Garden Centre Spider

Bugblog has curled under a dry leaf and enjoyed an extended period of dormancy. The new year has brought some interesting invertebrates so I foresee some blog activity in the next few days. In a trip to the garden centre, a little spider dangled from the ceiling. Something called my attention: its front legs. They were long and robust, and adorned with dark tufts of hairs. The spider held them forward, using them as feelers as it moved. It reminded me of an orb web spider, but not one I had seen before, so I posted a photo on Twitter asking for help. Within minutes, Chris @BHWWildlifeGdn answered:

@aBugBlog uloborus plumipes? commonly known as the garden centre spider
— Chris (@BHWildlifeGdn) January 19, 2015

A close up of the spider in my hand, to give you a sense of scale

And so it was! This species has been expanding in the UK since the early 90s, when it was found in garden Centres in Reading, Liverpool and Southampton. In fact, it is not even mentioned in my spider field guides. Now it is widespread through most of England and large cities in Scotland, where it is almost exclusively found in or around heated greenhouses of garden centres, and is thought to have come with plants from Holland, where it was also found. The original distributions appears to be Africa and the Mediterranean, although it is expanding worldwide thanks to its ability to thrive in garden centres.
 Uloborids are cribellate spiders, they brush their silk with a comb-like set of bristles in their rear legs making the silk sticky. This silk is so efficient immobilising prey that uloborids have lost their venom glands, not that this makes much of a difference to us, as this species is so small its fangs will be unlikely to break the skin.
 I shall keep an eye for this unusual spider every time I visit a garden centre. It builds horizontal orb webs (although it is not a member of Araneae, but of Uloboridae) and sits underneath, resembling a fragment of dead leaf and their egg sacs are white and of an unusual shape too. Chris recommended looking around the lights.

More information
Page for Uloborus plumipes at the Spider and Harvestman recording scheme. Here.
Wikipedia page.

Hitchhiker crickets

For about a couple of weeks, my six year old daughter has been telling me about the crickets in her school playground. Crickets? surely they would be grasshoppers, I said dismissively. I shouldn't have doubted her identification abilities, as she confidently pointed at oak bush crickets when presented with photos in a field guide, and my husband and son also confirmed it. I was most intrigued, as bush crickets are rare north of the Humber. Last week I spent an embarrassing amount of time searching for the mystery crickets while the kids played after school, while other parents I know looked at me as if I was going nuts. 'I put in on the tree this morning', my daughter would said, 'I've seen four, no... five' I wondered if the kids throwing sticks to get at the conkers was also dislodging the crickets from the chestnut tree at play time. I searched and searched, and, although I did find some Field Grasshoppers, Chorthippus brunneus, nearby there was no sign of the crickets, so frustrating!

  Today, at school pick up time, she told me she had rescued one from a puddle under the chestnut tree. I searched and initially found none, but finally, I found a live female and a very squished male on the ground, hoorray! Both were collected and taken home, and to my surprise they turned to be the Southern Oak Bush Cricket, Meconema medidionale, distinguished from the related Oak Bush Cricket by its stumpy wings and larger male cerci. Oak Bush Crickets are nocturnal and live in trees canopies, so they are thought to be under recorded, although they are attracted to light, so they turn up inside houses in the summer. Instead of singing by stridulating with their wings like other crickets do, males attract females by drumming with their rear legs on the substrate, and this sound can be audible up to 1 m away. They are predatory crickets, and feed on small insects like aphids and leaf-miners (including those of Cameraria ohridella, the Horse Chestnut leaf miner). Despite their name, they occur in many tree and bush species and are a late species, with adults found from mid August up to the first frosts.

 Since the 1960s, the Southern Oak Bush cricket expanded its distribution range from its original homeland in Italy throughout large areas of Northern Europe, and is now also found in North America. It was recorded in the UK for the first time in the autumn of 2001, and since then, it has spread north up to Nottinghamshire. Given its flightlessness, it is surprising how fast they are expanding. A study systematically searching for this species in the recently colonised Slovak and Czech Republics found that they are found mainly in urban habitats like parks or campsites, often with localised populations near car parks and main roads, suggesting that they might be dispersed passively by vehicles, especially trucks and caravans. They are, unexpectedly, often found on vehicles.

 The fact that several individuals are present suggests that the crickets have been around for a while in the school grounds. Would a teacher returning from a visit down south might be responsible from the introduction of this cricket species in Hull?

The squished male

Side view of the female

UPDATE 8/10/2014
We released the female on the chestnut tree. Although she had lost a leg, she was quite capable of jumping, and hid under a shrivelled leaf. I found a freshly dead male in the same spot, quite intact. Here he is. Look how much longer his antennae are compared to the female.

More information
British Orthoptera & Allied insects page. Here.

Grabenweger, G., Kehrli, P., Schlick‐Steiner, B., Steiner, F., Stolz, M., & Bacher, S. (2005). Predator complex of the horse chestnut leafminer Cameraria ohridella: identification and impact assessment. Journal of Applied Entomology, 129: 353-362.

Vlk, R., Balvín, O., Krištín, A., Marhoul, P., & Hrúz, V. (2012). Distribution of the Southern Oak Bush-cricket Meconema meridionale (Orthoptera, Tettigoniidae) in the Czech Republic and Slovakia. Folia Oecologica 39(2) 155-165.

Liana, A., & Michalcewicz, J. (2014). Meconema Meridionale Costa, 1860 (Orthoptera: Tettigonioidea: Meconematidae)–The First Record In Poland. Polish Journal of Entomology, 83(3), 181-188.

Horse chestnut scale insect

From April to July, tree trunks and branches in our street become mottled with Horse Chestnut scale insects. The bright white, powdery substance under the 'scale' is the ovisac, loaded with thousands of eggs. The scale is the dead body of the female, which has invested her effort into the production of the ovisac, after months of feeding on tree sap, and whose function is now protect the ovisac. The Horse Chestnut scale insect, Pulvinaria regalis, is an invasive species from Asia found in the early 60s and described from specimens in Paris in 1968. It is a generalist species, found mainly in urban environments and feeds on a diverse array of deciduous trees, and has a liking for Sycamore and Maples, Lime and Bay leaf tree.
  Scale insects do not look much like insects, do they? What we called scale insects are adult females, with flattened shiny bodies hiding tiny legs underneath, and piercing mouth parts like a shieldbug (scale insctsct are homopterans). Pulvinaria regalis has some mobility before egg laying. Both the first nymph instar (called crawlers) and adult males look more like a typical insect.
 Horse Chestnut scale insects hatch in summer and move onto the underside of leaves, where they feed.  Then, before leaf fall, they move back to the tree trunks and branches. In spring, mature males and females appear. Mature males are winged but do not feed, so they spend their short lives looking for females and mating. Females crawl to leaves, mate and start feeding on the tree sap and when fully mature and ready to lay, they move onto tree trunks to lay their ovisac. Although they can appear in such large numbers, they do not obviously cause much harm to mature trees, although saplings or weak trees may suffer from loss of sap. Scale insects, in particular eggs and nymphs, are the main food source for some ladybird species such as Exochomus quadripustulatus, the Pine Ladybird, no wonder they are also common on our street.

More information
GB non native fact sheets

A cool harvestman

Today I came across an unmistakable harvestman species, Dicranopalpus ramosus. This species has - or is in the process of - colonising Europe from its original home in North Africa. It is unclear if this expansion has or not anything to do with human transportation, but it has been suggested that it could could have been introduced with garden plants or horticultural produce, and the species has carried on expanding. It was first noted in the UK in 1957, and reported in Scotland in 2000.

 This is the second time I spot this harvestman. The first time (07/11/2009), was in the same location and also on a headstone (above). They have a typical resting posture, close to the substrate, with their long legs outstretched to the sides, and they often rest alongside leaves or branches this way. When resting on walls - or in this case on headstones - they are easy to spot. The second distinctive feature is that, their palps are forked. Males have a dark mask across the eyes and plain bodies about 4 mm in length, females have pale eye region and dark patterns in their body, palps and legs. 

Adults are found from the end of July onwards, peaking in September, apparently happy to live until February or March if the frosts don't kill them. 

A female

Male showing the usual stretched posture.

Close up of the same male.

No records were available for East Yorkshire, so these now have been uploaded into iRecord.

More information
Page in the British Spiders site.

An Australian invader

 
I have seen this moth quite a bit around in the garden since the 5th of March, and yesterday I took some shots of it and identified it as Epiphyas postvittana, the Light Brown Apple Moth. This Australian native leaf-rolling moth is a generalist feeder regarded as a minor agricultural pest, mostly of apples, in the UK, where it was introduced in the 1930s. The larva feeds on a range of fruit trees and vegetables, by making a silky retreat from which it can feed undisturbed. Adults are dimorphic and also rather variable, although males have a more sharply defined pattern (I think the one above is a male).
It is the first time I come across an Australian invader in the garden.

More info at UKmoths.

Ups and downs of ladybirds

I came across a 2 spot ladybird today on the way home (above, being checked by a garden ant). This ladybird species seems to have been the main loser in the Harlequin ladybird invasion, with a 44% decline since the harlequin arrived. They share habitat, and the small size of the 2 spot makes it easy prey of the harlequin when in the larval stage. The future does not bode well for the 2 spot. The same stretch of road where we found the lone 2 spot is a Harlequin hotspot: today there were tens of active harlequins, and we counted not one...

 not two...

 not three...

but five pairs mating.

A beautiful pair, but not for the lilies!

This pair of Scarlet Lily Beetles, Lilioceris lilii, was mating on my Asiatic lilies a couple of days ago. These shiny leaf-eating beetles have emerged from the soil, where they overwinter, just when lily shoots and leaves are well developed. Both adults and larvae are voracious and can quickly defoliated plants. I have posted on this species before, but you can submit your records to the RHS Lily Beetle Survey, where there is more information on the species.

Silent aliens

Have a look at these:

Harlequin Ladybird

Lily Beetle

Western Conifer Bug

They are invasive insect species in the UK. They are also so bright, or large, that they are hard to miss. You'll come across them even if you don't look. Many, many other alien invaders are harder to notice, they arrived, and before anybody other than specialist taxonomists noticed, they have spread across sizeable portions of the country. Many such silent invasions involve invertebrates that are small and or hard to identify.
  Clutches of snail eggs in the soil of pot plants, or dormant adults in cracks in stones or other cargo are often sent as inadvertent stowaways across countries thousands of miles away. They arrive in the destination, thrive and begin a quiet invasion. As many snails are tiny, and to the untrained eye they look identical to other snails, they are transported about very often. A sizeable fraction of the snails species of Central Europe is now thought to be of alien origin (about 15%), most of Mediterranean origin and the trend is of a recent increase, aided by increasing temperatures and commerce. In some extreme cases the ability of the snails to disperse is extremely limited, or their requirements for specific substrata so high that they scarcely move after introductions. Such is the case of Papillaria papillaris, a minute snail native of Italy, Sicily and Malta. These snails were likely to have been introduced in the UK in the 18th century with Italian ornaments or stonework, then prized by affluent stately home owners. Just two populations (in Brownsea Island Castle and Cliveden House) have been found so far. Amazingly, they have barely moved a few meters in this time, although they form self-sustaining colonies. Likewise, in Spain, this snail is restricted to walls and ruins from the Roman period, two millennia living practically where they were placed!
 Of course, there are many examples of the other extreme of the spectrum. Species that quickly spread on arrival, or after a lag period. An example is the Girdled Snail, Hygromia cinctella, a snail of Mediterranean origin which now is rapidly expanding in the UK. It was first noticed in the South in 1950, and it has now reached Glasgow, that is fast - for a snail. There have been suggestions that the snail might travel as stowaways in cars! Although this might seem outrageous, snails' habit of climbing up vertical surfaces and attaching itself firmly for aestivation or overwintering might facilitate this and it has been documented that this behaviour increases transport by cars. The girdled snail is 1 cm across and triangular when looked at from the side, with a pronounced keel that sports a pale line. At a distance looks like a juvenile garden snail. My daughter, however, noticed this snail on the pavement in my street a few days ago and it was necessary to rescue it from being crushed by passers by. I only noticed it wasn't a garden snail when I picked it up, after it had retreated into its shell.  I will keep a close eye and see if it has already arrived in my garden.

Side view showing the keel and pale edge.

Underside showing the lack of umbilicus

More information

Burçin Aşkım Gümüş and Henk K. Mienis (2010) Records of Papillifera papillaris affinis in continental Spain and their connection with walls and ruins from the Roman period. The Archaeo+Malacology Group Newsletter, 18: 1-4. here.

Janet Ridout-Sharpe (2010) Papillifera papillaris: a second colony is discovered in England. The Archaeo+Malacology Group Newsletter, 18: 1-6. here.

Alena Peltanova, Adam Petrusek, Petr Kment, Lucie Jurˇicˇkova (2011). A fast snail’s pace: colonization of Central Europe by Mediterranean gastropods Biological Invasions : 10.1007/s10530-011-0121

The impact of Harlequins on native ladybird fauna

Harlequin ladybirds (Harmonia axyridis) are one of the most obvious invasive species in the UK. They are large and voracious and there was much speculation on their potential negative impact on the native ladybird fauna, given that they are regular predators of other ladybirds, especially during the vulnerable larval and pupal stages. An open access paper published today by Helen Roy and collaborators uses a powerful combination of citizen science (in the form of Ladybird online surveys) and systematic surveys to address directly the impact of Harlequins on the distribution and abundance of eight once common and widespread ladybird species in the UK, Belgium and Switzerland. Their statistical analysis on geographic distribution addressed the impact of the arrival of Harlequins on each species for well-sampled km2.
 The results are very clear, but also worrisome: the arrival of Harlequins had a negative impact on the distribution of 5 out of 8 species in Belgium and on 7 out of 8 species in Britain. The effect was large and the affected species have now contracted in range. The effects were striking for the small 2 spot ladybird, Adalia bipunctata, - a tree specialist - , which declined a 30% in Belgium and 44% in Britain in the 5 years following the Harlequin arrival. Although some of these species that were already declining, the presence of the Harlequin intensified the rate of decline.

Figure 1 Effects of Harlequin arrival on the distribution of eight native ladybirds based on predictions for an average 1-km2. Prediction is based on the fixed effects of the models and ignores random variation in occupancy among specific 1-km2. Absent assumes the 1-km2 is not colonized by the Harlequin, and present assumes the 1-km2 was colonized in 2001 (Belgium) or 2004 (Britain) by the Harlequin. Note that our predictions are shown in the measurement scale (probability of occupancy), rather than the modelled scale (logit). (from Roy et al 2012)
  The systematic surveys of ladybird abundance in the tree habitats favoured by Harlequins supported these results and showed that the numbers of all native ladybirds decreased since their arrival, especially markedly in the UK. The only species relatively immune to their invasion is the 7 spot ladybird, a large species that favours herbaceous vegetation and is less likely to overlap in niche with Harlequins.
 Local or regional extintions of some tree specialist species seem like a certainty, and the impact this will have on agricultural systems is hard to predict. The following gallery is a celebration of the diversity of native European ladybirds, with the species used in the study.

Pine ladybird, Exochomus quadripustulatus

 Orange Ladybird, Halyzia sedecimguttata

A winter aggregation of 7 spot ladybirds, Coccinella septempunctata

Cream Spotted Ladybird Calvia quatuordecimguttata

 10 spot ladybird, Adalia decempunctata

2 spot ladybird, Adalia bipunctata

14 spot ladybird, Propylea quattuordecimpunctata

22 spot ladybird Psyllobora vigintiduopunctata 

More information
Roy, H., Adriaens, T., Isaac, N., Kenis, M., Onkelinx, T., Martin, G., Brown, P., Hautier, L., Poland, R., Roy, D., Comont, R., Eschen, R., Frost, R., Zindel, R., Van Vlaenderen, J., Nedvěd, O., Ravn, H., Grégoire, J., de Biseau, J., &; Maes, D. (2012). Invasive alien predator causes rapid declines of native European ladybirds Diversity and Distributions DOI: 10.1111/j.1472-4642.2012.00883.x


Gardiner MM, O'Neal ME, & Landis DA (2011). Intraguild predation and native lady beetle decline. PloS one, 6 (9) PMID: 21931606


Gagnon AÈ, Heimpel GE, & Brodeur J (2011). The ubiquity of intraguild predation among predatory arthropods. PloS one, 6 (11) PMID: 22132211

Is global warming erasing a melanism cline?

 The 2 spot ladybirds, Adalia bipunctata, I find in my garden are of the typical morph, red with 2 black spots, one in the centre of each wing case, but there is also a melanic morph in this species* - black with four red spots - and several rarer intermediate morphs, which are determined genetically. Some colour morphs tend to be more common in some areas than in others. This geographic variation is thought to reflect differences in temperature regulation between morphs. Melanic ladybirds benefit from thermoregulating more effectively in certain microclimates: when there is little, intermittent sunshine and is colder. This advantage becomes most important in early spring, when after emerging from hibernation ladybird behaviour is strongly limited by temperature, so the black ladybirds can start reproducing earlier. Paul Brakefield and Peter de Jong have studied the polymorphism in the two spot ladybird in Holland for 30 years. The two spot colour polymorphism, nicely matched the differences in climate between the warmer coast and the colder inland areas. At the beginning of their study period, in 1980, the dark morph was commonest inland, where it reached 60%, and its frequency decreased gradually towards the coast (less than 20%). Samples taken in the same transect since then show how the sharp decline in frequency of the dark morph gradually disappeared to the point that there was little if no differences between sampled areas in 2004, with the frequency of the melanics in inland areas dropping to similar levels than the frequency in coastal areas. Brakefield and de Jong think that the disappearance of this cline is a response of the ladybirds to the gradually warming climate in the area.

Figure 1 Changes over time in the proportion of the illustrated melanic and non-melanic morphs of the two-spot ladybird beetle along a transect of ca. 115 km in length in the Netherlands (bottom-left). Samples were collected in each of the 5 years indicated at 16 more or less evenly spaced localities from west to east. Colouring of years matches the histograms for melanic frequency in the individual samples from each locality. The panel on the bottom-right shows deviations in average temperature from a ‘normal’ season/year at De Bilt (red spot on map). From left to right, columns represent data for winter (Wi), spring (Sp), summer (Su), autumn (Au) and the overall year (Tot), respectively, and from top to bottom for different years beginning before the period of ladybird sampling. The colour of each block indicates the extent to which the average temperature in the particular season/year deviated from ‘normal’; white, no deviation, blue, cooler than normal (dark blue more extreme than light blue), red, warmer than normal (dark red more extreme than light red)(from Brakefield & de Jong, 2011)

The story has a second dark aspect. The researchers had trouble reaching acceptable sample sizes in the 2004 sampling season. They even failed to find 2 spot ladybirds in two localities where they previously had been abundant. They attribute the decrease in numbers of the 2 spot ladybird to the impact of the invasive harlequin ladybird, which reached Holland in 2002. Not only the melanism cline is gone, but the 2 spot seems to be dissapearing as well.

References

Brakefield PM, & de Jong PW (2011). A steep cline in ladybird melanism has decayed over 25 years: a genetic response to climate change? Heredity PMID: 21792220

*UPDATE
So it seems I do have melanic 2 spots in the garden (above). Thank you to Helen Roy, who curates the Ladybird survey site for the ID.

On the Western Conifer Seed Bug and Christmas trees

This large, striking bug entered the house at night through an opened window. It is the alien species Leptoglossus occidentalis, the Western Conifer Seed Bug, a native from western North America, where is a minor pest of conifers. This species has long antennae and large rear legs, a pale zig-zag mark on the wings, and distinctly flattened and enlarged tibia, which gives the name to its group, the leaf-footed bugs. During last century, this species spread across North America and during the last decade has also been introduced in Europe, where it has quickly spread from the initial introduction point in Italy. It was accidentally transported in timber, and its spread could also possibly been aided by Christmas tree shipments. Nymphs and adults feed on the sap of cone seeds and buds, and therefore the damage is restricted to seed production. In continental Europe, where there are established populations, it does not appear to cause much damage. Every now and then, there are migratory influxes to the U.K. from the continent, as occurred in 2008. The bug often falls in moth traps, and is a good flyer. It is most obvious in the autumn, when it moves about looking for suitable hibernation sites, often entering buildings and sometimes forming large aggregations, attracted by pheromones produced by males. Nymphs have been found in a few sites in the U.K., so it appears to be establishing.
 If you have seen this bug, you can report it here.

References
Lis, Jerzy A., Barbara Lis & Jerzy Gubernator (2008). Will the invasive western conifer seed bug Leptoglossus occidentalis Heidemann (Hemiptera: Heteroptera: Coreidae) seize all of Europe? Zootaxa, 1740, 68-68
Taylor, S.J., G. Tescari & M. Villa (2001). A nearctic pest of Pinaceae accidentally introduced into Europe: Leptoglossus occidentalis (Heteroptera: Coreidae) in Northern Italy. Entomological News, 112, 101-103.
Blatt, S. & Borden, J. (1996). Evidence for a male-produced aggregation pheromone in the Western Conifer Seed Bug, Leptoglossus occidentalis Heidemann (Hemiptera: Coreidae) The Canadian Entomologist, 128 (4), 777-778 DOI: 10.4039/Ent128777-4

A red lily beetle

I spotted a handsome, bright scarlet beetle, hiding under a lily leaf. It didn't take long to identify it as the red lily beetle, Lilioceris lilii, with its long antennae and black legs and head. I took it to the white bowl and it showed two behaviours that may have helped this species expand its range from Asia to many temperate areas following horticultural Asiatic lilies: it plays dead when handled or disturbed and flies readily. The adult and larvae feed on lilies and fritillaries of many species and they can defoliate the plants very quickly. They have a single generation per year: the adults emerge in september and overwinter in the leaf litter. When the lily leaves appear the adults wake up and mate. They lay bright red eggs in lines underneath the leaves and the larvae, which are also red, disguise themselves on their own fecal matter, so that they resemble fragments of dirt.

The species was first introduced in the UK in 1943 and has recently expanded quickly in range. Now is present all over England, and parts of Wales and Scotland. Two species of parasitoids have followed the expansion of the beetle into the UK.

More information

The red Lily beetle website.

Alien Invaders

Today I saw the first Harlequin ladybirds of the year. Two individuals adjusting their position in a railing to catch the winter sun. In September 2006, I came across a beautiful, but strange, ladybird. Yellow, large and with 21 spots, I had never seen anything like it, and it wasn't in the insect guide I checked at home. A few weeks later, I found a large black ladybird with black spots. I had a little plastic container with me and took the insect home to photograph it. This time I took a bit more time to identify it. It was a Harlequin, a non-native ladybird species that since 2004 it has rapidly spread across the UK. The Harlequin is native from Asia, and has been widely used as pest control in greenhouses, from where it has escaped. The species had spread invasively in the USA and mainland Europe, from where it invaded the UK.
 This ladybird is unique in that it shows a large variation in color patterns between individuals. The following photos, all taken in Hull, illustrate this.

There was already a very well organized survey to follow the spread of this species in the UK, the Harlequin Ladybird Survey, and I reported these sightings. Data sent by members of the public (in the form of records and photographs) have helped to follow this invasion in great detail. This series of maps from the survey's website show the spread of the Harlequin in the UK year on year.
There is lots of info from the website, not only on the Harlequin, but also on the native ladybirds. You should be able to identify not only the adult ladybird, but also the larva. Here you can compare it with a 7-spot larvae.

Harlequin ladybird larva (with two lines of reddish spiky tufts on top of abdomen).

A 7-spot ladybird larvae (only black tufts on top of abdomen). Tufts are not obviously spiky.

Should we be concerned? Despite the Harlequin being a quite handsome bug, there are fears its explosive spread could result in threats for other ladybird species, either directly or indirectly. They are reportedly very aggressive toward other ladybirds and even humans! Although I must say I have often collected them by hand and they seem not to be aggressive when being handled carefully, in the same way the 7-spot. They eat larvae and eggs of ladybirds if aphids become scarce. Their populations might not be kept in check by predators and parasites. Also, they hibernate in houses in a communal way and they can become a nuisance.

 In Hull, the Harlequin became very common in 2007, but didn't see many in summer 2008, maybe the gloomy, wet summer didn't suit them!