Stinky sticks

I keep black beauty stick-insects, Peruphasma schultei which hide, not by looking like vegetation but by being black, velvety (hence non-reflective) and nocturnal. However, although usually calm when handled, they do have active defences which I discovered recently when retrieving a large females that had escaped to climb the curtains. I felt something wet on my hand, and when I looked there was a milky, eye-wateringly acrid liquid. I knew that a lot of stick-insects can spray defensive chemicals but hadn't witnessed this one before. Fortunately a quick Google told me that this had been investigated by Dossey et al. (2006), who discovered a new defensive compound that they named 'peruphasmal' after the insect producing it.

Peruphasma schultei

Peruphasmal is an isomer of dolichodial, a compound in the iridoid group.

structure of dolichodial

Iridoids are found in many plants (usualy in the form of glycosides) and may be active ingredients in those used medicinally. They are also likely to have a defensive function, protecting the plant against herbivores. Dolichodial and its isomers are found in plant essential oils, and as in this case, in the defensive sprays and secretions of some insects, possible being sequestered from food plants, or being produced by the insect's metabolism (they are intermediate compounds in the production of alkaloids for example). My P. schultei are fed on privet (Ligustrum sp.) which is in the family Oleaceae, one of those known to produce iridoids, so sequestration is plausible. The toxin in Ligustrum appears to be the glycoside syringin, known originally from lilacs, but now known to be a white, crystalline, bitter toxin in many plants including privet, hence its alternative name 'ligustrin'. So, this is a likely candidate for the source of the insect's defence. In plants, iridoids are usually bound to glucose, and peruphasmal is also sprayed along with glucose. Whatever the source - there is more research, but not much - it is an effective defence; my reaction was to put the insect down and wash off the secretion - a predator would have been sprayed in the face...



References

Dossey, A.T., Walse, S.S., Rocca, J.R. & Edison, A.S. (2006). Single-insect NMR: a new tool to probe chemical biodiversity. ACS Chemical Biology 1(8): 511-514.

Black beauty - no, not the horse.

I've posted a few times about my stick-insects - Macleay's Spectres (Extatosoma tiaratum) and can report I now have a lot (like, a pint!) of eggs. They were certainly fecund. I'm not currently raising these however, as I have a different species after a friend sent me a batch of eggs of Black Beauty stick-insects (Peruphasma schultei).

Whereas E. tiaratum are fairly common, P. schultei are not, at least not in the wild. They come from northern Peru and are known only from a 5-hectare area at 1200 - 1800 m altitude in the Cordillera del Condor, a mountainous area known as one of the world's biodiversity hotspots. There they feed on pepper-trees (Schinus spp.) but in captivity, are happy with privet, lilac and honeysuckle (and probably some other small shrubby trees too). They prefer drier conditions (40-60% humidity or thereabouts) than species from more humid areas of the tropics and should be fairly straightforward to keep without expensive equipment. They were only discovered and described in 2002 (Conle & Hennemann, 2005) and relatively little is known about them, although tyhey are popular and are cultured and shared around the world without being collected from the wild. 

This means that although there are plenty of care-sheets on the web, they tend to say exactly the same thing based on not-that-much hard evidence - so, amendments and new info is always useful. For example, I have since found out that they are remarkably good at dying. As the hatchlings tend to hide during daylight, they sometimes crawl beneath things, get stuck and starve. So, no more newspaper in the bottom of the hatchery. Some simply failed to thrive, while others were eaten by a larger specimen that turned cannibal despite having plenty of leaves. They are now segregated more carefully and I'm raising a second batch of eggs alongside the original cannibal. Problems aside, they are rather splendid - velvety black except for reddish mouthparts (and when mature, wing-flaps) and yellowish eyes - they are sometimes called golden-eyes stick-insects. Here they are:

New hatchling. Note the white bands near the tips of the antennae.

Side view of about a 3rd instar nymph looking for something to climb onto. The kinked antennae are due to a problem during the most recent moult.

Good view of the reddish mouthparts and yellow eyes.

In 'scorpion' posture. Note the wing-buds.

Reference

Conle, O. V. & Hennemann, F. H. (2005). Studies on neotropical Phasmatodea I: A remarkable new species of Peruphasma Conle & Hennemann, 2002 from Northern Peru (Phasmatodea: Pseudophasmatidae: Pseudophasmatinae). Zootaxa 1068: 59-68.

Cretaceous Crato creature 2

Though I do look at a lot of invertebrates, I rarely delve into palaeontology - however, a little while ago I did look at a bug from the Crato Formation (about 110-125 myo) in Brazil. I recently went shopping online again and found another one listed only as an 'insect' and not at all expensive, so (as the images looked fine) I decided to go for it and see if I could identify it myself. This is what appeared:

My 'new' Cretaceous Crato insect

It is by no means a large insect - the body is about 12mm long, the cerci (or 'tails') about 15mm if straightened, and the wingspan around 18mm. Using Bechly (2007), it didn't take long to determine that this is a mayfly, an adult or almost-mature 'subimago', probably of the family Leptophlebiidae. Apparently it is found reasonably often, but its taxonomic position is unclear - it may even be in a different family and is known simply as 'species 1'. So, that's as far as my identification can go - basically, it's a mayfly but beyond that nobody really knows. However, this doesn't mean its features can't be examined more closely...

Cretaceous mayfly: Leptophlebiidae (?) sp. 1

The head, thorax (orange and fairly uniform) and abdomen (speckled with pale pimples) can be clearly differentiated and four of the legs are visible, indicated by green arrows. The abdominal segments and midline, though slightly deformed are also visible (see the drawing below) as are the large forewings. The dark line extending top-left may be another leg - it's certainly about the right size.

Right forewing of Leptophlebiidae (?) sp. 1

The front margin of the wing is well preserved, along with sections of some of the veins radiating from the base, and some areas of the wing membrane itself. Not bad for its age... I think the outline suggested here is quite accurate as the shape is similar to other specimens, though maybe a little of the hind edge is missing.

The pair of long cerci, typical of this species (well, taxon - it might be one of several similar species) - note the thickened bases.

So, having investigated the main features, I decided to follow the methodology of other palaeontologists and produce a line drawing to try to elucidate the detail without the distraction of mineral colours and textures - these are useful when looking at some features, but a hindrance for others. By photographing, printing, tracing and scanning, this is what I came up with:

Line drawing of my specimen of Leptophlebiidae (?) sp. 1

Personally, I'm quite happy with this - although the wing membranes (for example) are lost here, the body segments are a little clearer and I think a sense of the overall level of preservation is clear e.g. the slight fragmentation of the cerci. Such specimens are generally given a catalogue number including an abbreviation of the museum they are in e.g. NHM 23438 would be specimen 23438 in London's Natural History Museum; maybe this mayfly should be DSH 00002, the second fossil insect in my collection of curios...

To finish, it's worth noting that the Leptophlebiidae are still around - there are about 2000 species worldwide, including 6 in Britain, though they have 3 cerci (one reason why the species here is of uncertain family), and the larvae have forked gills on their abdomens giving them their common North American name of 'prong-gilled mayflies'.

Reference

Bechly, G. (2007). Insects of the Crato Formation. In: Martill, D.M., Bechly, G. & Loveridge, R.F. (eds.). The Crato Fossil Beds of Brazil: Window into an Ancient World, Cambridge UP, pp. 142-426.

Fascinating toxic frogs

I'm moving away from my usual topic today by looking at a species that is neither British nor invertebrate - the green and black poison arrow frog Dendrobates auratus. Poison arrow/dart frogs (they have several non-scientific names) are familiar to many people because of their toxicity and bright colours, but what is actually known about them?

Dendrobates auratus showing green and black colouration.

Well, first of all, although there are around 175 species of arrow/dart frogs (all in the family Dendrobatidae), only 3 are known to be used to coat blowpipe darts with poison, and none of these are in the genus Dendrobates. So, we know that the common name is not an accurate description - good start! Now onto a little background info.

Found in humid lowland and submontane forest and secondary vegetation up to about 1,200m altitude, D. auratus is native to Central America (Costa Rica, Nicaragua & Panama) and NW Colombia and, although many dendrobatids (like many amphibians worldwide) are rare and/or decreasing, this species is not currently threatened in the wild, being rated as of 'Least Concern' by the IUCN. There are also some feral populations in Oahu, Hawaii following a release of around 200 frogs in 1932 as an attempt to control non-native insects - these bred successfully and their descendents persist in the island's mountains and valleys (McKeown 1996). It is a highly variable species with at least 15 distinct colour forms known in the wild - as well as the typical green shown above, there is yellow, largely black, largely brown and the rare blue which is known from the Pacific side of Panama, but threatened with extinction due to clearance for agriculture, which fragments the habitat, though the species as a whole can live around humans (e.g. in parks, gardens and rubbish dumps (Heselhaus 1992, Ostrowski 2009). Being small (c. 20-40mm depending on form) and brightly coloured, tt is a popular pet among keepers of exotic herpetofauna and over-collection may be an issue, although there is a thriving captive breeding trade supplying much of the demand.

It is a semi-arboreal species, conducting much of its activity in trees up to some tens of metres above the ground but descending to the ground to travel between trees as it can not jump between them. Climbing is aided by pads at the ends of its toes (visible in the photo above). Females lay clutches of 3-13 eggs on leaf-litter which the male guards (Heselhaus 1992); they hatch after about two weeks and the male carries tadpoles to stagnant water in a tree-hole, leaf axil of a bromeliad, or small ground-level pool (van Wijngaarden 1990). The tadpoles feed on protozoans and rotifers, metamorphosing after 39-89 days, with sexual maturity being reached in 6-15 months, and a life-span of at least 6 years in captivity (Zimmermann & Zimmermann 1994). Females compete for males, attempting to monopolise them and being known to destroy the eggs of rivals (Summers 1989). If you would like to hear a brief recording of their call, go here.

Although not the most poisonous of dendrobatids, it is toxic enough to make a human unwell with skin glands producing an alkaloid derived from the ants that form much of the wild diet (Caldwell 1996). This reduces the risk of being attacked by predators such as theraphosid spiders AKA tarantulas (Gray et al. 2010), although some of the development of toxicity (e.g. in different popualtions, and captive-bred individuals fed a wild diet) are not fully understood.

So, to finish, why did I decide to look at this species? Well, it is a charismatic species and makes a change from my long run of invertebrate posts. I am also a member of Hampshire Conservation Volunteers - our logo is a frog so we adopted a D. auratus (now named 'Den Bates') at Marwell Wildlife and I wanted to know more about it - if you like this idea, the yellow and black D. leucomelas is still available for adoption...

Mate-guarding in Dendrobates auratus

References

Caldwell, J.P. (1996). The evolution of myrmecophagy and its correlates in poison frogs (Family Dendrobatidae). Journal of Zoology (London) 240(1): 75-101.
Gray, H.M., Kaiser, H. & Green, D.M. (2010). Does alkaloid sequestration protect the green poison frog,
Dendrobates auratus, from predator attacks? Salamandra 46(4): 235–238.
Heselhaus, R. (1992). Poison-arrow Frogs: Their Natural History and Care in Captivity. Blandford, London.
McKeown, S. (1996). A Field Guide to Reptiles and Amphibians in the Hawaiian Islands. Diamond Head Publishing, Los Osos, California.
Ostrowski, T. (2009). Dendrobates auratus.  [accessed 13/08/2012].
Summers, K. (1989). Sexual selection and intra-female competition in the green poison-dart frog, Dendrobates auratus. Animal Behaviour 37(5): 797-805.
van Wijngaarden, R. (1990). Enkele klimaatgegevens en waarnemingen in de biotoop van de gifkikkers Phyllobates vittatus en Dendrobates auratus. Lacerta 48(5): 147-154.
Zimmermann, E. & Zimmermann, H. 1994. Reproductive strategies, breeding, and conservation of tropical frogs: dart-poison frogs and Malagasy poison frogs. In: J.B. Murphy, K. Adler and J.T. Collins (eds). Captive Management and Conservation of Amphibians and Reptiles. Society for the Study of Amphibians and Reptiles, Ithaca (New York). Contributions to Herpetology Volume 11, pp. 255-266.

Wheels of life

Straight in with a question today - have wheels evolved in nature? Now, I know it's been written about before, and there's no shortage of discussions on any number of online forums (or fora if you prefer), but it's something I've been musing on and coming up with some underlying questions - so, here goes with one my rare forays into the more speculative realms of biology and ecology...

Firstly, why might wheels be a useful adaptation? Well, they could provide an efficiency and simplicity of motion in some circumstances - I can certainly imagine animals using wide wheels to trundle across the soft sediments of the ocean floor for example (much like the wire-wheeled lunar rovers from Apollos 15-17). However, legs and fins generally work pretty well, with wheels really coming into their own on straight, smooth, hard surfaces. These are not common in nature, though humans produce plenty of them - and hence plenty of wheels. So, a lack of evolutionary advantage might be one reason why natural wheels are not widely seen.

Secondly, what do I even mean by a wheel? Here, I am only considering something that has an axle or bearing. There are plenty of organisms that roll - the South American pebble toad Oreophrynella nigra that tumbles down slopes to avoid predation, the wide variety of tumbleweed plants (and the rarer 'tumblefruits' such as Physaria) that disperse seeds as they roll with the wind, and the puffballs of the genus Bovista that are also blown around and so disperse their spores more widely. Ocean currents roll the coral Porites lutea across the sea floor and the small stomatopod mantis shrimp Nannosquilla decemspinosa can curl up and roll slowly like a wheel if stranded on a shallow damp sandy shore, thus returning to the sea. These are all interesting in their own right, and there are other examples, but none of them are wheels.

In fact, there don't appear to be any organisms that roll along on wheels in the way that humans' various vehicles do. As mentioned above, there may simply be no evolutionary pressure to produce a wheel, but there are also developmental constraints. For example, to have a wheel in a multicellular organism is tricky because, to be able to rotate freely, the wheel needs to be detached from the rest of the organism. If this is the case, how could it maintain a blood supply, neural connections and so on? Two options come to mind:

1. The wheel could be made of 'dead' material secreted by the organism, such as carapace material. This could grow as a toroid (doughnut-shaped) swelling on a limb/axle and gradually separate by thinning near the limb. This could produce a passive wheel on an axle much like a wood-turner produces a freely movable (but not removable) ring from a single piece of wood.
2. The wheel could be alive but self-contained. If a ring of cells developed as above and then detached, to be an effectively autonomous wheel, it would have to have its own energy supply (photosynthesis, chemosynthesis?) and so on.

Neither of these options have been discovered in nature, though this does not mean they never will - my feeling is that the lack of need is more likely to prevent wheels evolving than developmental problems. So far, I have not differentiated between passive and active wheels i.e. whether they simply roll like a cart (reducing the friction that would be caused by dragging) or are actively rotated by an energy source. Active wheels are developmentally even more problematic as a torque needs to be applied - in animals, motive force is produced by muscles, but this would not work on wheels as they need to be freely rotating. However, in bacteria, the problems of producing motive force, overcoming inertia and so on have been solved. In fact, the only example discovered so far of a true biological wheel (an active one that produces continuous propulsive torque around a fixed structure), is the bacterial flagellum, the  a propeller-like thread used for locomotion. Where the flagellum enters the cell membrane, there is a motor protein that works like a rotary engine, powered the flow of hydrogen ions (i.e. protons) across the bacterial cell membrane down a concentration gradient created by a proton pump. A similar system using a sodium ion pump exists in the genus Vibrio.

The structure of the flagellar base showing cutaway details of the 'motor'. Thanks go to Mariana Ruiz Villarreal for putting this and other diagrams in the public domain.

At an even smaller scale, the enzyme ATP synthase (which is involved in energy storage and transfer within cells) is somewhat similar to bacterial flagellar motors and is likely to be an example of modular evolution i.e. where two separate structures or sub-units (which evolved and previously functioned separately) become joined or associated, and in doing so gain a new function.

So, although true wheels have not been discovered in multicellular organisms, and both developmental and utility constraints make their evolution highly unlikely, maybe impossible, there are ways that wheels might be used in nature:

1. Through symbiosis, joining two otherwise unrelated structures/organisms in order to get round the developmental problems preventing direct evolution of wheels. This could be instinctive (imagine an extension of dung-ball rolling by dung-beetles) and is an idea which has been explored in fiction, e.g. in the Amber Spyglass (Philip Pullman, 2000). In this book, an alien race known as the Mulefa use large, round seed pods as wheels. They put these on sideways-oriented claws (which act as axles) on two of their legs, using the other two legs to push themselves along. The symbiotic aspect occurs because the trees that produce the seed pods depend on the rolling action under the weight of the Mulefa to break open the pods and allow the seeds to disperse and germinate. A number of other science fiction novels consider biological wheel use in a variety of ways, but Pullman's is probably my favourite so far, though other examples include David Brin's Brightness Reef (1995) and Infinity's Shore (1996), and Wheelers (2000), co-authored by Ian Stewart and Jack Cohen (who happen to be a couple of Terry Pratchett's collaborators if you like a bit of nerd-trivia).
2. Through tool use. Humans do this, using wheels widely - could other species do the same, even if with less technological sophistication? I'm just waiting to see corvids start rolling past...

OK, I think that's enough speculation for one day - if anyone out there does know of other examples of 'bio-wheels', I love to hear about them, so feel free to add a comment.

OMG in the OMZ: massive marine microbes

Today, I'm drawing inspiration from the Census of Marine Life, a decade-long project which has produced a huge inventory of marine life - a baseline catalogue to be used for further research and to inform the management and conservation of marine life. The Census looked at all scales from microbes to whales, at all latitudes and at all depths. The Census has produced a range of books, both popular and technical - one of the most straightforward and non-specialist, 'Citizens of the Sea' (Knowlton 2010) provided a couple of snippets that induced me to delve into the detail rather more...

First up, megabacteria - not the disease of budgies (which is actually a yeast), but very large true bacteria discovered off the coast of Chile and Peru in the 1960s. Placed in the genus Thioploca, the bacteria are filamentous and 2 to 7 cm (yes, cm) long. Secreting mucus, they form vast mats (the largest covering 130,000 km-sq) in/under the 'oxygen minimum zone' (OMZ), an area at 40-280 m with very little dissolved oxygen; instead they have to rely on hydrogen sulphide in the sediments. They oxidise this using nitrates (from sea water) which they can concentrate up to 500 mM in the liquid vacuole that occupies over 80% of their cell volume, even though the concentration of nitrates in sediment is only around 25 μM. Mucus-sheathed transport filaments send this nitrate 5–10 cm down into the sediment and reduce it, thus oxidising the hydrogen sulphide and creating a coupling of the nitrogen and sulphur cycles in the sediment (Fossing et al. 1994), producing pyrite and elemental sulphur as a result (Ferdelman et al. 1997). Thus, organic matter (in the form of anaerobic dissolved organic carbon) can be oxidised at low oxygen concentrations. The mats also provide food and shelter for a range of animals including squat lobsters (Pleuroncodes monodon), amphipods, and ophiuroids (Grupe 2011). As the OMZ shares features with conditions during the Proterozoic period (2.5 bya to 650 mya), and similar microfossils have been found, such bacteria may provide an insight into ancient life forms and ecology as well as performing a still little-known but key function in nutrient cycling. Research is ongoing with one recent example investigating Thioploca found in Danish waters where (in the species T. ingrica) nitrate accumulation was lower at around 3 mM, with bicarbonates and acetates used as carbon sources, and no mat being formed (Høgslund et al. 2010). 

A core from a Thioploca bacterial mat. The core is about 8 cm across and the mat about 1 cm thick. The mat is made up of many bacterial filaments with individual cells visible to the naked eye as white threads. Huge for bacteria! Photo courtesy of NOAA/Lisa Levin.

Now, ocean acidification due to carbon emission from fossil fuels may affect marine microbes - with microbial ecosystems responsible for between 50 and 90% of all marine biomass and over 95% of marine respiration, they maintain Earth's habitability though their influences on climate (they can sequester atmospheric carbon dioxide), nutrient cycling and the decomposition of pollutants (Leahy 2012). So, this could be very serious indeed and current research is looking at the  sensitivity of marine microbes to acidification. If I find links to results from this research, I'll post an update, plus I have some more bacterial and marine posts (among others) in the pipeline.

References

Ferdelman, T.G., Lee, C., Pantoja, S., Harder, J., Bebout, B.M. & Fossing, H. (1997). Sulfate reduction and methanogenesis in a Thioploca-dominated sediment off the coast of Chile. Geochimica et Cosmochimica Acta 61(5): 3065-3079. Fossing, H, Gallardo, V.A., Jørgensen, B.B., Hüttel, M., Nielsen, L.P., Schulz, H., Canfield, D.E., Forster, S., Glud, R.N., Gundersen, J.K., Küver, J., Ramsing, N.B., Teske, A., Thamdrup, B. & Ulloa, O. (1994). Concentration and transport of nitrate by the mat-forming sulphur bacterium Thioploca. Nature 374: 713-715.
Grupe, B. (2011). Sea Floor Habitats of the Chile Margin. NOAA Ocean Explorer [accessed 15/02/2012].
Høgslund, S., Nielsen, J.L. & Nielsen, L.P. (2010). Distribution, ecology and molecular identification of Thioploca from Danish brackish water sediments. FEMS Microbiology Ecology 73(1): 110-120.
Knowlton, N. (2010). Citizens of the Sea: Wondrous Creatures from the Census of Marine Life. National Geographic, Washington DC.
Leahy, S. (2012). Giant Bacteria Colonize the Oceans. Tierramérica. [accessed 15/02/2012].

Is it a hornet? No, it's Britain's biggest fly

At first glance, Britain may not stand out as the home of impressively large insects - the largest beetles are tropical, as are the stick insects, large water bugs and largest butterflies. We do have some large dragonflies such as the Emperor Dragonfly Anax imperator, and a male Stag Beetle Lucanus cervus is always striking, but Britain is not home to the 'island gigantism' seen in, for example, the Giant Wetas of New Zealand, particularly the Little Barrier Island Giant Weta or Wetapunga Deinacrida heteracantha, the world's largest orthopteran (grasshoppers & crickets). The world's largest fly is Gauromydas heros, a member of the family Mydidae found in Brazil. It can be up to 60 mm long (excluding appendages) and is a wasp mimic, but relatively little is known about it with few specimens being collected as the adult lifespan appears short.


However, Britain is not without its own sizeable flies as noted during a visit to Hatchet Pond yesterday. Although used heavily for recreation, this site is home to many uncommon plant and invertebrate species, and one of these was this striking insect seen shortly after arriving.

The Hornet Robberfly Asilus crabroniformis, Britain's largest fly.

This is of course the Hornet Robberfly Asilus crabroniformis, Britain's largest species of fly, seen here resting on a dry stick in damp grassland. Although it can't rival G. heros, large specimens are about half its size with the body length varying from 18-28 mm (this individual was at the upper end of the range).


Despite the large size and bright yellow abdominal section (it is a hornet mimic), it is remarkably well camouflaged when the brown wings cover this area. As it is a 'darting' hunter (capturing prey via short darting flights, usually of no more than 50cm, but sometimes up to 3m), this cryptic colouration is presumably important, while defense may also be involved as it has been seen hanging upside-down when resting at night, a position that displays only the cryptic brown colours of the underside - in this position it has the appearance of a dead curled-up leaf (Clements & Skidmore 1998). The hunting flights are launched from low-lying perches such as the stick in the photo above; prey items are large insects such as grasshoppers, larger beetles and flies, butterflies, moths, bees and wasps (WBP 2008) and take 10-30 minutes to drain using the fly's sharp piercing mouthparts (Stubbs & Drake 2001).

A. crabroniformis is associated with a range of open habitats such as heath and various types of grassland with rough shrubby vegetation, and is associated with old dung with females laying their eggs on or under the crust, particularly cow dung, though also horse and (if in mounds) rabbit. Despite this fairly broad habitat requirement, it is a local species rarely found in large numbers. The map below (courtesy of the National Biodiversity Network) suggests a fairly widespread distribution in southern Britain; however, some of these records date from before the loss of much of its habitat (especially in East Anglia) - most recent records are from the heaths of Dorset, Hampshire (as here) and Surrey, plus chalk grassland in Hampshire and Wiltshire, with scattered records elsewhere.

Distribution map of Asilus crabroniformis in Britain (as of 08/08/11)

Although it has no specific legal protection, it was listed as Notable (scarce) by Falk (1992) who noted key threats as:

• Habitat loss/degradation due to conversion to intensive agriculture or forestry.
• Loss of dung and associated beetles due to removal of appropriate grazing animals e.g. replacement of cattle by sheep in much of its historical Hampshire habitat (Stubbs & Drake 2001) and removal of dung during paddock management (WBP 2008). Sheep dung appears to be unsuitable for A. crabroniformis and the shift from cattle to sheep accelerated during the BSE outbreak of the 1990s (Clements & Skidmore 2002).

Since then, Stubbs & Drake (2001) have also noted a new threat in the form of avermectins used as a veterinary treatment to remove parasites from the guts of livestock. In some cases, this makes dung harmful to the dung beetles which appear to be important in the fly's life cycle (see below). Further, WBP (2008) suggest a possible effect of climate change as adult activity appears to be temperature-regulated (i.e. reliant on high ambient air temperatures), though it is unclear whether this would simply increase levels of adult activity and if so, whether this would be beneficial or harmful.


The life cycle is not fully understood, but the later-instar larvae are free-living in the soil and thought to be predatory on dung beetle larvae (geotrupines such as Minotaur Beetle Typhaeus typhoeus) which are associated with herbivore dung. The diet of early-instar larvae is unknown as eggs are laid in dry dung which has no large insect larvae, only small invertebrates such as nematodes and springtails. Territorial behaviour has been suggested, centred on dung-pats (e.g. by Stubbs & Drake 2001) but this has never been clearly demonstrated with Clements & Skidmore (2002) indicating no strong territoriality following their mark-recapture study - indeed individuals could be seen sharing parches and previous records of agression may be attempts at copulation. Clements & Skidmore (2002) found the mean adult lifespan to be 15.9 days in the field with peak emergence in late July and August following a larval lifespan thought to be 2-3 years, although this is not well documented (WBP 2008).


Regarding conservation, it seems clear that this is a scarce species which has declined over recent decades - it is therefore of key importance to understand the combination of habitat and stock-related factors which may benefit it, especially as even historical records appear to show populations as being somewhat erratic with local ones becoming extinct as others appear. However, this shifting distribution may be threatened with collapse if suitable areas of habitat become isolated, especially as research suggests dispersal rates may be limited with individuals rarely moving more than a few hundred metres, and often less (Clements & Skidmore 2002). This, a range of conservation measures need to be considered:

• Maintain rotational grazing management by suitable species to ensure a continuous dung supply.
• Prevent excessive scrub invasion of suitable habitat while ensuring a range of vegetation type/structure.
• Reconsideration of the widespread use of avermectins.

These are simple enough in concept, but of course not so straightforward to implement. Asilus-friendly habitat management should be quite easy to achieve (at least in principle, assuming the time and resources to control scrub etc), though beyond the bounds of the nature reserve it is less clear how the loss of cattle dung can be reversed. However, education of land-owners is important and simple measures can ensure a continuous supply of horse dung, although again it will require a considerable change in behaviour to reduce the use of avermectins which are popular broad-spectrum treatments. In the end, this is a charismatic species which, with a little effort and creativity, could be more widely known and popular as 'Britain's biggest fly'.




References

Clements, D.K. & Skidmore, P. (1998). The autecology of the Hornet Robberfly Asilus crabroniformis L. in Wales, 1997. Countryside Council for Wales Contract Science Report No. 263. Bangor.


Clements, D.K. & Skidmore, P. (2002). The autecology of the Hornet Robberfly Asilus crabroniformis L. in Wales, 1997-1999. Countryside Council for Wales Contract Science Report No. 525. Bangor.

Falk, S. (1992). A Review of the Scarce and Threatened Flies of Great Britain (Part 1). NCC, Peterborough.

Stubbs, A. & Drake, M. (2001). British Soldierflies and their Allies. BENHS, Reading. 

Worcestershire Biodiversity Partnership (2008). Hornet Robberfly Asilus crabroniformis Species Action Plan. [accessed 08/08/11]

Beetle Carnival! An Inordinate Fondness #16

It's been a quiet week or two for me on the blogging front - too much of the paid stuff to do. Still, I knew that for once I had a post booked in advance - issue #16 of the beetle-focused blog carnival 'An Inordinate Fondness'. This is the first time I've hosted a blog carnival (my own blog's not even a year old yet), so where to start?

Well, at the (conceptual) beginning with an excellent post about being drawn into beetling in the Ozarks, the acquisition and building of equipment, and occasional bouts of wifely disapproval - here's Basic Beetling by the Ozarkian. This has a few larger beetles illustrated (though we all know how many are tiiiiny) and mentions the assumption that they'd all be large - like The Perching Dung Beetles of Wongabel by BunyipCo. Apparently, in the Neotropics, dung beetles arrange themselves by size on perches, something that - if you wish to observe it - means sitting out in the rainforest at night; sounds good to me!

Anthocomus rufus (nope not featured anywhere else here!)

Sticking with the dungy theme, plus locations that seem exotic from my location in suburban southern England, the Natural History Museum (to me, the 'Mother Ship') would like to tell us all about the 2nd part of their expedition to Tanzania, this time to the Udzungwa Mountains where it appears they had to Exit, pursued by... a buffalo. Having done plenty of East African fieldwork in my time, I know the feeling... Still, despite the tetchy vertebrates, they found some fine dung beetle specimens using dung-baited traps, and more - including a mystery cerambycid - what more could you want? Well, what about the charismatic scarabaeid Paracotalpa ursina from Sam Wells Bug Page. These were recorded in an ordinary city park in Fresno, showing that witnessing their weighy grass-stem-toppling antics doesn't require a well-funded research trip to a remote 'corner' of the globe.

Hmmm... how about a paper on 'voyeurism in the Coccinellidae'?

Next, and switching families, here's some excellent tiger beetle photography from beetle-friendly ant specialist Alex Wild at Myrmecos (one of my personal favourite invertebrate blogs)? Marvel at the metallic green-ness, fear the mighty mandibles, but you can't avoid the gaze of Alex's Six-spotted Tiger. Also looking at cicindelids, AIF's very own Ted MacRae takes a look at some recently published work on the Rediscovery of Cicindela scabrosa floridana; as with any such rediscovery of something thought to be extinct, there is optimism about it being extant, tinged with concern about its long-term prospects. More research, and hopefully effective habitat management, will tell... In the meantime, don't forget to check out Ted's identification challenges!

Off to a couple of photography sites now, starting with something a little smaller than a dung or tiger beetle - I just love Giraffe Weevils so thanks to Kurt at Up Close With Nature as they don't exist in my part of the world. I was similarly pleased by the Headlight Beetle at Nature Closeups; a Costa Rican click beetle (elaterid) with bioluminescent spots on the pronotum, and something I had never heard of even though there are apparently numerous such species spread across several genera.

Not a monkey on my back - a weevil on my finger...

Getting back to a bit of 'diagnostic morphology' (one of my favourite aspects of entomology), and finally introducing some carabids which I've so far neglected in this post, Dave Ingram at Island Nature has been searching Vancouver Island for beetles and tracked down a mystery carabid - why not take a look and see what the Backyard Beetle turned out to be. He's also been looking at introduced European species which I am familiar with such as this Gorgeous Ground Beetle.

And finally [insert fanfare here], we return to the Natural History Museum's Tanzanian expedition to try to find out the identity of their mystery cerambycid at And the beetle you have been waiting for... Will it be identified, will it remain a mystery? Head over to find out, and maybe check out their latest video offering too.

One of my specialist group, the Chrysomelidae - leap, tiny flea beetle!

And so we finish - I decided to illustrate this post with a few fairly random beetle photos of my own - better photographers than me are featured in the carnival links above, but please do have a browse around my site. It's not all beetles, and some posts are even about things with bones, though invertebrates do play a major part. I hope you enjoyed this carnival; next month's AIF#17 will be at Biodiversity in Focus so don't be shy - submit a post or two, and maybe even host (it's quite easy) - it's what makes the carnival go round!

Cretaceous Crato creature!

Last year, I was mooching around some fossil sites online and found some insects for sale. They were from an old collection and had originally been collected from the Crato Formation in Brazil. Many interesting specimens had already been sold, but among those remaining was a rather nice little beetle (according to the seller) around 12.5mm long excluding appendages. Such items are popular with collectors (including plenty with more money than me), but this one had been broken in half and neatly glued. So, still complete, but less popular with collectors and hence more affordable. Result! I bought it...

Here it is - my Cretaceous insect complete with crack, but otherwise in good condition.

...and so, it has sat in my curio cabinet for a while, until today I decided to find out more about it. First of all, the location. The Crato Formation is of Early Cretaceous age and is found in the Araripe Basin of NE Brazil. It is an important Lagerstätte (an undisturbed fossil accumulation, and today's first new word) which has yielded many important fossils - the decay conditions (or taphonomy - new word no.2) are unusual and mean that limestone accretions formed nodules around dead organisms, preserving more soft parts than is usually the case; there have even been Odonata specimens with preserved iridescence, and fish with their stomach contents preserved! The strata were mostly laid down mostly during the early Albian Age (approx 108 mya) in what was then a shallow inland sea. Crato has long been considered part of the Santana Formation (also important for palaeontology), but this is about 10 my younger and the two have now been formally separated.

Sadly, local mining activity damages the sites and a significant trade in illegally collected fossils has developed over the last decade or so. As such specimens are likely to be lost to science (not to mention incidental damage to the site), paleontologists are quite rightly calling for an urgent preservation programme - I'm glad that my specimen was legitimately collected and studied well before this became a problem; a reminder to check the provenance of anything like this, particularly for non-specialists like me who might otherwise not be aware of problems with particular sites, however well known to specialists.

So, I know it's a bit more than 100 my old, and it might be a beetle - what next? Well, as I've mentioned before, I'm no palaeontologist, but it's time to take a closer look...

The front half.

The two circular structures in the middle of this picture almost look like they could be eyes, but they are behind the sinuate line that I think must be the rear of the head or front of the pronotum. These, along with the yellowish 'figure-8' behind them, and the white subtriangular 'shield' behind that, appear to be the underlying attachments and musculature below the pronotum - possibly attachments between the prothorax and pronotum, and/or the attachment points of the elytra. The eyes appear quite bulbous and between them is a blunt protrusion - the mandibles or other appendages?

The thorax and abdomen.

Moving further back, there is a central division (about in line with the crack) and this looks very much like the rear of the pronotum. Behind this is a white area in the centre of the abdomen, surrounded by darker oblique abdominal segments; nothig too surprising there. The legs appear fairly simple and are all present - in front of the head is what might be a thickened front left femur, but I can't tell for sure - certainly the other femur looks somewhat thickened where it joins the tibia. Now, time to zoom in a bit more...

The tip of the front left leg.

The legs don't appear to have any major adaptations or obvious spines, and going by the above picture, terminate in a single straight to slightly curved claw. Moving onto the head, there seems at first to be few features, but closer examination provides a little more, at least tentatively:

Close-up of mouthparts.

Close-up of left eye (the circle is approx 0.3-0.5mm across).

 

An even closer look at the left eye.

The blunt protrusion at the front of the head does appear to be the mandibles, and they appear fairly simple (there's just a hint of a serrated join between the two halves, or is that wishful thinking aided by the handy placement of crystals of rock?); in any case there's little more to be seen here. However, zooming in on the left eye (the better preserved of the two), does reveal some interesting detail. Within the blue circle above is an area that, down the microscope, is not only shiny, but also has a few surviving ommatidia (lenses of the compound eye). At this point, my camera can do no better, but I hope that you can see some of these (six or so, faintly at the centre of the blue circle). They appear to be separated (unlike a mosaic arrangement), and thisis seen in some modern beetles (as well as the trilobite fossil that's also in my cabinet). Now moving rearwards again...

Close-up of part of the pronotum/thorax.

Close-up of abdominal segments.

 The pronotum shows layers of tissue in close-up; both what looks (to me) like chitinous material, and a small amount of what I think is soft tissue - the small folded purplish area just below the centre. The abdomen shows a similar mixture of textures, and I have to wonder whether the faint striation in the centre is the remains of muscle fibres, some other structure, or an artefact of preservation. Any thoughts on this are most welcome.

Close-up of the tip of the abdomen.

 Lastly, looking at the tip of the abdomen, what appears to be the pygidium (rear-most segment) is visible. This looks like a pair of curved 'pincers' but I expect is simply an artefact of preservation i.e. a gap left when the fossil formed. Still, some insects do have structures like this, so it could be something genuine - again, ideas are gratefully received and it would be great to be able to identify some reproductive apparatus...

So, after all that, what do I think I've got? Well, going by the general shape and simple legs, I thought it was probably a water beetle - something like the family Noteridae ('burrowing water beetles') which is already known from Crato/Santana. This example shows some similar features - leg form, overall shape, the round pronotal attachments behind the head. However, a message from Beetles In The Bush (see below) provided a quite different hypothesis. The eyes are where I think they are (the ommatidia are a good clue!), and the femurs are enlarged, and likely to be raptorial. The 'mandibles' appear to be the clypeus (so, the 'serrated join' mentioned above is an artefact/wishful thinking after all), and the revised ID is that it's a belostomatid hemipteran - a group still around and known at the 'giant water bugs' (which I've seen plenty of on my travels), although this one is less giant than many. The body shape is right, and having looked at some other images of fossil belostomatids (like this), the oblique abdominal segments are closer than seen in water beetles. Like the Noteridae, they've been found at Crato before and have one of the best fossil records of any insect group (presumably because of their large size and relatively frequent/rapid burial in shallow waters). So, I have a new (and better) ID, but I'm open to suggestions and further hypotheses. It's not the beetle I thought I'd bought, but it's still excellent and I remain fascinated by it - I'd love to learn more; I do have an 'Atlas of Macroinvertebrate Fossils', but it's only got two insects in it which are nothing like this.

Lastly lastly - for a brief extract from the 'insect' chapter of 'The Crato Fossil Beds of Brazil' (Martill, Bechly & Loveridge, 2007, Cambridge University Press), look here. For more about the whole book (it's not cheap though, RRP £92), look here (Amazon has a 'look inside' link for this title too). Soooo tempting...

All the lonely beetles, where do they all come from?

Shortly before World War II, London’s Natural History Museum published the first edition of Common Insect Pests of Stored Food Products (Hinton & Corbet 1943), a slim volume providing a guide to the identification of such insects. Although not specifically covering beetles or non-native species, the topic is such that many of the species covered were indeed beetles, and that are number of these were introduced to Britain. However, it was not until the publication of Volume 1 of Insect Travellers (Aitken 1975) that the beetles recorded from cargoes imported into Britain were surveyed and presented comprehensively, whether or not they were seen as pest species. In Volume II (Aitken 1984), which covered insects other than beetles, the numbers, types and origins of cargoes were updated,  and extended to cover the period 1957 to 1977. The 1970s saw a shift from cargo stowage in ships’ holds towards the use of freight containers; in turn this led to the decline of ‘traditional’ ports with piecemeal unloading which allowed for easier inspection and application of insecticides. Therefore, ship and wharf inspection was virtually superceded by increased vigilance inland by the 1970s e.g. at the end points of cargo distribution such as factories, warehouses, mills and farms.

Fast-forwarding to 2010, a lot has changed. Britain now has a Non-native Species Secretariat (NNSS) with its associated Non-native Species Information Portal (NNSIP) of factsheets currently in development. In 2005, Natural England undertook an ‘Audit of Non-native Species in England’ which tabulated 2721 species and hybrids, of which 98 were beetles. Looking at these, the origins/native ranges can be approximately split as follows:

Europe 43

Australasia 16

North America 10

Asia (as a whole) 5

Eurasia 5

East Asia 3

South America 3

‘Tropics’ 3

Central America 2

Palaearctic 2

Africa 1

Europe & Africa 1

South Atlantic islands 1

Unknown 3

Although there is some doubt about the origins of some of these (e.g. a few listed under ‘Europe’ could turn out to be Eurasian), by far the most prevalent source of non-native beetle species is elsewhere in Europe, even though Asia, and especially China, is often cited anecdotally as such a source. It is true that many non-native plants originated in China, and that increased Chinese exports are likely to increase the transport of species from East Asia. However,  it should also be remembered that some Chinese beetles found in Britain and elsewhere are particularly striking such as the Asian longhorn beetle (Anoplophora glabripennis) and the citrus longhorn beetle (Anoplophora chinensis). These have in turn induced the production of many factsheets and column-inches about their invasiveness and damage to timber (e.g. Haack et al. 2010) and that the Internet allows much faster and broader familiarisation with such species than was the case when introductions were first being catalogued.

Asian longhorn beetle (Anoplophora glabripennis)

While other invertebrates may show a similar pattern (of 34 spiders on the NNSIP register, 20 are from Europe and none are strictly Asian), looking at new and potential invasive species as a whole (i.e. including all animal taxa) shows a different pattern. For example, since their 2005 audit, Natural England’s horizon-scanning (Parrott et al. 2009) highlights 63 species across its red ‘alert’, yellow ‘watch’, ‘black’ and ‘climate’ lists; of these, North America (13), East Asia (12) and Asia (9) are the key areas of origin with only 5 species originating elsewhere in Europe and 7 more widely in Eurasia.

There are many factors here, but some seem to stand out; 

• Beetles move by many means, often helped by humans, but many introductions into Britain are likely to be from Europe as their ranges expand northwards with climate change.
• Many terrestrial invertebrates, especially small species, can spread to new areas unaided – this is seen with ‘ballooning’ spiders.
• Larger species, particularly invertebrates are often spread intentionally such as fish species introduced for angling or ornamental purposes and subsequently escaping or being released.

So, to return to the title question ‘...where do they all come from?’, the answer is that they are from more-or-less everywhere, but often just across the English Channel – for those of us interested in species recording and finding new beasties, they are likely to keep us busy and there will no doubt be further striking exotics hitting the headlines as they appear in fruit shipments and imported houseplants. Meanwhile, the small and less obvious beetles will be making their quiet way from continental Europe...

References

Aitken, A.D. (1975). Insect Travellers. Volume I. Coleoptera. Technical Bulletin 31. Ministry of Agriculture, Fisheries and Food. HMSO, London.

Aitken, A.D. (1984). Insect Travellers, Volume II. MAFF Agricultural Development and Advisory Service Reference Book 437. HMSO, London.

Hinton, H.E. & Corbet, A.S. (1943). Common Insect Pests of Stored Food Products. British Museum (Natural History), London.

Haack, R., Hérard, F., Sun, J., & Turgeon, J. (2010). Managing invasive populations of Asian longhorned beetle and Citrus longhorned beetle: a wWorldwide perspective Annual Review of Entomology, 55 (1), 521-546 DOI: 10.1146/annurev-ento-112408-085427

Parrott, D., Roy, S., Baker, R., Cannon, R., Eyre, D., Hill, M., Wagner, M., Preston, C., Roy, H., Beckmann, B., Copp, G.H., Edmonds, N., Ellis, J., Laing, I., Britton, J.R., Gozlan, R.E. & Mumford, J. (2009). Horizon Scanning For New Invasive Non-native Animal Species in England. Natural England, Sheffield. (Natural England Contract No. SAE03-02-189, Natural England Commissioned Report NECR009).

Thank you to the US Fish & Wildlife Service for putting this image in the public domain. Much appreciated.