Cemetery Bugs

There is a large cemetery nearby and today me youngest daughter came with me and decided to have a bug safari. It was the first visit in the year that I have taken many more invertebrate than bird photos.

A pine Ladybird on orange lichen, Xanthoria parietina 

A group of the blind millipede Blaniulus guttulatus, with Porcellio scaber and a while slug under a piece of wood

A colourful cluster of Harlequin ladybirds appeared to have emerged from a crack in a damaged tree and some were flying off

Peacock sunbathing

A carpet of Lesser Celandines

Flowering Willow

Harlequins and Amaurobius (with nests?) under broken headstone.

Overwintering

 BugBlog has been dormant for a few weeks. Somehow, posts somehow never went past the project status. But today, the sun shone after days of rain and gloominess, and in a walk at the park, my 4 year old and I did an informal ladybird survey. We checked many tree trunks and spotted lots of ladybirds, not as many Harlequins as other years, but still the easiest ladybird to find in the park. They were quite active as it was mild, and walked on the tree trunks in the sun. More than 40 in total, as the cluster of Harlequins above nestled in a little hole on a tree trunk was a little tricky to count. A single 2 spot ladybird completed the survey.

Inside curly cherry leaves with their food

Yesterday we gave our cherry tree a light trim, removing shoot tips damaged by the black cherry aphid. The leaves curl up, sheltering hundreds of aphids (above). Inside the leaves, with their prey, there were hundreds of Harlequin larvae larvae, a few 2 spot larvae and with few adults of both species, a 10 spot ladybird and a few predatory hemipteran bugs.

A mirid bug Deraeocoris ruber (I think!)

10 spot ladybird, near a black cherry aphid

Fully grown Harlequin larvae

2 spot ladybird larvae

Two spot ladybird

An unusual 2 spot ladybird with 3 spots!

Cherry wars

The new shoots of my cherry tree are covered on Black Cherry Aphids, Myzus cerasi. The new leaves are stunted and folded, sheltering the aphid colonies which produce abundant honeydew - loved by bees and bumblebees. Ladybirds have also arrived at the tree in search of the aphids. There are many Harlequin ladybirds, mating, feeding and laying eggs (above).

Today, tens of Harlequin egg clusters were very obvious under the leaves...

...often close to aphid infestations. 

One of the clusters was already hatching: a new generation of Harlequins 

There were also many 2 spot ladybirds on the cherry, I am not sure they are as advanced on their life cycle as the Harlequin, although this pair was mating. Given the strong impact of Harlequins on 2 spot populations, it is obvious there is more than one war going on in the cherry tree. All the photos, except for the top one (26/05/12) taken today.

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.

Lay them and eat them

During the past week, Harlequins have become more noticeable. I spotted a few walking on a tree trunk in my street. Today, passing by the same tree I had a look and saw many clusters of bright yellow-orange eggs laid on small crevices on the tree trunk, they are not wasting time! One of the Harlequins seemed to be laying (above). I also noticed that some egg clusters looked like they had been partially predated. The culprit is not hard to find: Harlequins are known by their cannibalistic tendencies, so - hungry after winter - , they may turn to eat eggs laid by other ladybirds. They also may be able to eat their own unfertilised eggs.

A Harlequin stretching its wings in the sun

A cluster of eggs

Harlequin near cluster with predated eggs

A close up of another cluster. Note the chewed up egg on the top right hand side.

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

Twelve bugs of Christmas

Today we woke up to a mild, sunny day and I was pleasantly surprised by the diversity of active bugs about. I made a count of species and when I got to twelve I was reminded of the traditional carol and made up a buggy version:

12 ladybirds walking | 11 winter-gnats dancing |10 honeybees buzzing |9 bluebottles basking | 8 leafhoppers leaping | 7 woodlice hiding | 6 hoverflies flying | 5 snails sleeping | 4 spiders weaving | 3 harlequins | 2 drone flies | and a bumblebee on ivy

The honeybees in the local wildlife garden were coming out tripping over each other and ladybirds (7 spots mostly but also harlequins and 22 spots) were awaken by the mild temperature. I counted 5 spider species outside (Tegenaria, Zygiella, Pholcus, Steatoda, Linyphia). The main surprise was the bumblebee worker, extremely fast and active and with pollen baskets full with pollen.

Here is a slideshow of bugs seen and photographed today

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.

The face of the alien aphid muncher

This Harlequin ladybird happily eating an aphid on the 6th of November illustrates how active many of these ladybirds still are. I found young and old larvae, pupae, mating adults and also dormant adults in a small area near in my local park. Harlequins are multivoltine, and will carry on reproducing as far as conditions are suitable. In northern Europe, two generations and possibly three if weather conditions allow can occur, as adults do not need to enter dormancy before they can reproduce, as it is the case with the 7 spot ladybird.

The maladapted parasite

There is a corner in my local park which is always teeming with Harlequins. At this time of the year adults ready to hibernate and grown larvae about to pupate dot the railings and fenceposts. A couple of days ago I came across this individual dragging a strange large lump behind as it sluggishly walked on top of a railing. I took a photo and wondered if it was a parasite. Parasites in Harlequins are very interesting, as, this ladybird being an invasite species, they might be adapting to the newcomer and helping keeping this species in check. Richard Comont, from the Centre for Ecology and Hydrology in Wallingford, after checking the photo commented:

It looks like a Dinocampus which has got caught up in the ladybird's wings - I think you can just about see some segmentation at the bottom of the yellow lump. Dinocampus seem to be a bit disorientated in Harlequins - they seem less able to fully paralyse the adults on the way out - so possibly might sometimes emerge from the top of the abdomen, from between the tergites rather than the sternites, which could result in the emerging larva ending up in the wing like this.
Dinocampus, on emerging, usually parasitise their host ladybird, cutting the nerves connecting the legs to the nervous system, and potentially also the tendons of the leg abductor muscles which allow the ladybird to move its legs away from its body (so that when the parasitoid's cocoon is spun between the ladybird's legs it can only be clutched tighter). However, Harlequins with Dinocampus are often not fully paralysed, and instead stumble around slowly, almost drunkenly.

It appears that some native ladybird parasites are also attempting to parasitize the newcomer invasive Harlequin, which is encouraging. Evolutionary success for parasites in expanding their host range to include Harlequins however, will only come if the parasite is successful completing its life cycle in the new host. The offspring of the parasite must actually be able to become a successfully reproducing individual in the new host, and the disorientation of the Dinocampus in Harlequins, which could often result in their larvae being unable to spin its cocoon under the host - which is walking around dragging it - suggests that their success in surviving and actually becoming an adult parasite might still be far lower than in the native ladybirds. They still might have some way to go.

I am most grateful to Richard Comont for allowing me to reproduce his comments in this post and to Lori Lawson Handley for kindly forwarding my photo to some knowledgeable ladybird experts.

UPDATE
From an e-mail from Richard Comont (15/11/11):

I’ve found a couple of these ‘parasitised’ Harlequins today – and the ‘parasite’ was just a pool of reflex blood, which the wing had folded around into a kind of bag – no evidence of parasitism at all!

That's science for you!

Queens, harlequins and admirals

The last mild, sunny days of autumn are bringing out scores of insects. Standing under a large flowering ivy today the sound of buzzing bees, bluebottles, droneflies and wasps was extraordinary, especially given that November is only a couple of days away. Yesterday, six red admirals sunnied and gorged themselves on the ivy blossom. They are charging batteries before their migration to South Europe and North Africa.

Red Admiral and passing droneflies on ivy

 A green shieldbug, Palomena prasina, climbing a tree.

 Today, a queen Bombus hypnorum fed on lavender flowers. 

 A female Araneus diadematus spider sat proudly on her silky egg cocoon. 

Honeybees on ivy flowers

Dozens of harlequins and 7 spot ladybirds flew about landing on a sunny wall and leaving again.