Wildlife garden meadow unfurling

The meadow in the wildlife garden is growing fast, speckled with buttercups and with the wide geranium and cranesbills carpeting it. Today it was warmer than previous days, with sunny spells. In the morning, I checked for insects and spiders. Female wolf spiders, at least two species, basked with their egg sacs. I also spot several nursery web spiders, I try to get close without spooking them, slowly crouching down to their eye level. When they bask, they often cross their front legs in front of them (above), but if they sense danger, they spread them out or just dash down into the grass. I see several males, each of them with a distinctive colour pattern.

Rhopalus subrufus

The large narcissus fly, Merodon equestris, many around, my first of the year.

A Scatophaga sp. fly

A Lucilia sp. greenbottle

Mating 14 spot ladybirds.

An unfortunate 7-spot ladybird fell prey of the teasel.

Wolf spider with egg sac.

Amber snail, many on the rotting vegetation around the ponds edge.

Cheilosia sp. a hoverfly on a buttercup.

Mating Corizus hyoscyami

A very pale grey male.

The same male than the top shot.

No butterflies, today, just a few Mint moths, Pyrausta aurata, in the marjoram.

Hairy shieldbug

This side shot of a Hairy Shieldbug, Dolycoris baccarum, in the wildlife garden, shows well where its name comes from. Its hairiness does not show in a more usual top shot (below).

Bug heads

Dead heading is one of the rules of gardening, isn't it? You are told to remove the faded flowers so that seeds don't form, as they extract lots of energy from the plant. But what will you miss? you want to look at seedheads. In a walk around my local wildlife garden I found that meadow cranesbill's seedheads were busy with shieldbugs of several species, feeding on them. Among the bugs there were some striking black and red ones (above), which I had never seen before, they were very flighty and the light conditions were not right, but I managed some shots. Upon looking into the British Bugs site I identified them as Corizus hyoscyami a species that during the last decade has expanded throughout England from a few coastal locations in Wales, another species that, according to the NBN gateway, wasn't known to have crossed the Humber before.

Corizus hyoscyami feeding on developing cranesbill seeds

Nymph Green Shieldbug, Palomena prasina

Rhopalus subrufus, one of the most abundant today

The first Green Shieldbug Palomena prasina adult of the year

Likely Corizus hyoscyami nymph. Thank you to Dave who identified it in a comment.

Dolycoris baccarum Hairy Shieldbug

This dark Forest Bug, Pentatoma rufipes, had a ride home on my trousers 

I must remember to leave my geranium seedheads for next year, as true bugs (hemiptera) are one of my favourite insects. One job less to do, and plenty of opportunities to enjoy bugs.

More awakenings

 The early spring temperatures continued today. Ants were scouting out of their nests, sage leafhoppers were active and honeybees and droneflies enjoyed the Laurustinus. I waited until the bee and the dronefly visited the same inflorescence to take the above shot. I wonder if the Laurustinus flowers change colour when they are pollinated, in the same way as the Horse Chestnuts, white when fresh and turning red when already pollinated and stop producing nectar. 

We counted over 100 7-spot ladybirds in the garden. Some were eating aphids on the spurge.

The entrance of the burrow of a large Amaurobius spider under a garage roof. If you click to embiggen you can see the remains of a wasp a Harlequin and some wings I cannot identify, possibly from bluebottles.

A green shieldbug, Palomena prasina, on its dark winter attire came out of its overwintering refuge.

 Wolf spiders enjoyed the sun on the sunny side of the garden.

A new adult generation of Woundwort shieldbugs

Every day I check the Lambs ears for the Woundwort (or Bronze) shieldbugs, Eysarcoris venustissimus. They are usually immobile and once you've found them once, they are easy to find, although they will hide under the leaves if they feel threatened. They form clusters on the tips of leaves, not only of the Lambs ears, but also on the Enchanter's nightshade, which covers the ground on this side of the garden. Today I spotted the first adults of the year, four of them, one on a cluster of final instar nymphs; another, still white (above), looked like it had just moulted into adulthood.

A new and shiny adult Woundwort shieldbug adult on Lamb's ears

A fresh adult with three final instar nymphs

These are some nymphs on the seed stalks of Hedge Woundwort: their colours make them almost invisible at a distance, as the stalks also have a contrasting green/black pattern.

Lambs ears shieldbugs

Although I keep Lambs ears (Stachys byzantina) in the garden for the benefit of the Wool Carder bees this plant also attracts many other bugs. They provide a lot of structure with their large woolly leaves, and spiders, harvestmen and ladybirds are often found on them. They also offer sheltered overwintering opportunities. My other favourite lambs ears bug is a true bug, the pretty shieldbug Eysarcoris venustissimus, also known as the Woundwort shieldbug, as their usual feeding plant is the native Hedge Woundwort (Stachys sylvatica). This is a small shiny bug that appears in a single generation per year. The adults are bronze, grey and white with fine black speckling. They emerge from hibernation in April and can be found mating on May. Females lay their eggs in Stachys plants. Nymphs can be easily found on July and August and by September there is a new adult generation. Today, I watched at least nine nymphs in various stages of development on the Stachys plant. Nymphs are green and black or pinkish and black. All the nymph photos were taken today. 

An early instar nymph. The object near it are seeds of Circaea luthethiana

A group of Wounwort shieldbugs with a green shieldbug nymph.

A last instar nymph. They can be recognised by their black wing buds

A mating pair on Stachys bizantina (11/5/11)

UPDATE 25/08/11. Replaced a photo with the early instar one.

Bug babies leave their siblings

After at least ten days clustering together on top of their egg cases, the 28 Green Shield Bugs, Palomena prasina, nymphs finally left their siblings after moulting into a greener instar. This is the sequence of events:

12/7/11

13/07/11

20/07/11 All have now moulted into the greener 2nd instar

22/07/11. The nymphs start to disperse in the morning.

22/07/11. After an hour, only three reluctant nymphs remain on the egg cases. In the evening they had all dispersed. 

Some of the adventurous nymphs. I found one a meter away from the egg cases.

Poisonous bug babies cluster together

These newborn green shieldbugs, Palomena prasina, look most unlike adults. They have a bright black-red warning colouration in their first instar, for a few days they cluster tightly together on top of their egg shells. After moulting into their second instar they change colour to green and black and they disperse away from their siblings. All shieldbugs, including nymphs have stink glands between the first and second pair of legs. If handled roughly they can release repellent chemicals and they are often brightly marked. But why do these bugs cluster together?
 The contrasting black and yellow or black and red patterns of Cinnabar moths, ladybirds, Burnet moths, bumblebees and wasps are visual signals to potential predators indicating that the animal is distasteful, poisonous or dangerous in some way. The predator, having had a nasty encounter with the aposematic organism learns to avoid it. But how does does aposematism evolve in the first place? You would think that the first aposematic individual either dies or is injured in the process, so it cannot be though natural selection, right? One possibility, first suggested by Sir Ronald Fisher in 1958 is aggregation of related aposematic organisms:

For, although with the adult insect the effect of increased distastefulness upon the actions of the predator will be merely to make that individual predator avoid all members of the persecuted species, and so, unless the individual attacked possibly survives, to confer no advantage upon its genotype, with gregarious larvae the effect will certainly be to give the increased protection especially to one particular group of larvae, probably brothers and sisters of the individual attacked. The selective potency of the avoidance of brothers will of course be only half as great as if the individual itself were protected; against this is to be set the fact that it applies to the whole of a possibly numerous brood

Fisher's hypothesis of kin selected aposematism has been questioned recently. Although aposematic organisms tend to be gregarious, phylogenetic analysis suggest that aposematism evolved before gregariousness, so aposematism makes gregariousness easier to evolve, and not the other way round.
 Birgitta Sillen-Tullberg carried out some elegant experiments showing that aposematism can give direct benefits to the individual, and that kin selection is unnecessary. She presented hand reared Great Tits (Parus major) with two colour forms of the same bug species (Lygaeus equestris), one grey and black (cryptic), and the other - the common form-  red and black (aposematic). A group of tits was presented with cryptic prey and another group with aposematic prey in 11 trials per bird. Great Tits learned to avoid both cryptic and aposematic prey - remember both are equally distasteful - but attacked cryptic prey more readily from the first trial.

In addition, when attacked, aposematic prey survived more, indicating that the tits were more wary when attacking it.
Being grouped, though, can confer further advantages. Gabriella Gamberale and Birgitta Tullberg carried out experiments testing the effect of grouped versus solitary prey - bugs, Spilostethus pandurus - on learning avoidance by predators - chicks in their experiments. Chicks learn to avoid aposematic shieldbugs in fewer predation attempts, and were less likely to attack twice they are aggregated than if the prey is solitary. They concluded that gregarious aposematic prey are a more effective signal for the chicks to learn, the reasons why this could be are still unclear.

References
Fisher, Ronald A. (1958). The Genetical Theory of Natural Selection Dover Publications, Inc. Other: 0-486-60466-7
Sillen-Tullberg, B. (1985). Higher survival of an aposematic than of a cryptic form of a distasteful bug. Oecologia, 67 (3), 411-415 DOI: 10.1007/BF00384948
Gamberale, Gabriella, & Tullberg, Birgitta S. (1996). Evidence for a more effective signal in aggregated aposematic prey. Animal Behaviour, 52 (3), 597-601 DOI: 10.1006/anbe.1996.0200

A Hawthorn Shieldbug

We came across a couple of Hawthorn Shieldbugs, Acanthosoma haemorrhoidale, on a large hawthorn hedge at the edge of our local park yesterday. This is a strong contender for the most beautiful British shieldbug, large and shiny, with bright green and red markings, finely punctured and with broad, pointy "shoulders". They are found in a range of trees and shrubs, but their favourite food is haws, the berry produced by the Hawthorn, although they also feed on leaves or other fruit such as apples, piercing them with their rostrum, their sucking, needle-like mouthpart. As other shieldbugs, they overwinter as adults, often darkening their colours at the end of autumn, and emerge in the spring to feed and mate. Eggs are laid around May and the nymphs develop during the summer into increasingly larger stages quite different in colour to the adults. The new adult generation would emerge in August.
 Until recently, the Hawhorn shieldbug was common only in southern england, but his distribution has expanded north recently and now can be found in Scotland too.

A Hawthorn Shieldbug on Hawthorn

Final stage Nymph (2nd August 2008)