Monday, 30 April 2012

Chirping lily beetles

The sun shone in all its glory to end this most rainy April. Many insects came out of their temporary hiding places to dry out and enjoy the warmth. Some of these were Scarlet Lily Beetles. I wasn't sure if I had an infestation, as I had collected just a couple of adults in the last few weeks, but today I found 12, the first ones were a mating couple. As I found them I placed them in a plastic pot, and while I was carrying it I noticed a faint chirping call. I thought that there must be a nest nearby with calling chicks, but then I realized that the sound was actually coming from the pot: the disturbed Lily beetles were stridulating! when I touched them, they chirped repeatedly. You can watch this short clip of them in the pot, as I push them inside the pot, they chirp - I was trying to place the camera on the pot opening to improve the sound recording, but they kept climbing up the pot.

The first description of the stridulation of this beetle was written by the early entomologist René Antoine Ferchault de Réaumur in 1737:
when one holds it, it lets a little cry be heard, produced by the friction of its last abdominal segments against the elytra, the more one presses the elytra against the body, the louder it cries
More recent studies have confirmed this description, and also shown that stridulation is common in the Lily Beetle subfamily (Criocerinae). The stridulatory apparatus consists on a file on the last tergite - the dorsal end of the abdomen - made of microscopic parallel ribs, which are scraped by files of sharp denticles in the underside margins of the elytra. The sound is produced while the abdomen contracts, and these contractions can be amazingly rapid, up to 200 times per minute and is loud enough to be heard if the beetles are less than 30 cm from your ear. The high variability of the chirps and the situations in which they are produced suggest that this behaviour is a defence mechanism: the beetle will chirp if captured and the sound can startle the potential predator to release the beetle before swallowing it. In other beetle species chirping is used in intraspecific communication, with the lily beetle, is is yet another way of avoiding being eaten.

More information
Michael Schmitt & Dieter Traue. 1990. Morphological and Bioacoustic Aspects oî Stridulation in Criocerinae (Coleóptera, Chrysomelidae). Zool. Anz, 1990, 225: 225-240.

Sunday, 29 April 2012

Another girdled snail

I spotted this Girdled Snail, Hygromia cinctella, the second ever I have seen, climbing up a wall in my street a couple of days ago. The white whashed wall made a white background for it and I was pleased to get to photograph the live snail as it went about its business.

Saturday, 28 April 2012

A bumper year for 7 spot parasites?

In the last few days I have found quite a few 7 spot ladybirds parasitized by the wasp Dinocampus coccinellae in the garden: live ladybirds snared to a silky cocoon underneath them. Today I did a quick count and found eight. You can see their portraits on this post. This is being a successful year for 7 spots: there are so many around it is hard not to get one or two ladybirds in the background of any bug photo I take! It is no surprise that ladybird parasites are enjoying this ladybird bonanza. If you want to find out more about the rather gruesome Dinocampus life cycle click here.
One on sage
on the conservatory frame
a second one on the spurge
one under a Lamb's Ears leaf
An odd one, with the cocoon on one side on a bougainvillea leaf in the conservatory
one on an orchid in the conservatory
a second one on sage

Thursday, 26 April 2012

Dinner of the green bug muncher

After the very rainy April we are having a teasel growing in the garden is looking very luscious. It has grown a large rosette of leaves, and developed two large leaf-cups which are filled with water to the rim. If you want an account on this fascinating carnivorous plant, check here. I had a peek a couple of days ago to check if any drowned invertebrates were visible. And there were indeed! On the bottom cup (above) a 7 spot floated on a very cloudy liquid, while on the top one, a drowned slug was visible at the bottom of the clearer water, and a few small unidentified insects. What a catch!

Wednesday, 25 April 2012

The end of the affair

As the solitary bee herald of spring, Anthophora plumipes, is my favourite bee. It is with some sadness I found this dead male on the path today. The rain might have contributed to its demise, but it might also have reached the end of its natural life. In my patch, the first males appear at the beginning of March, and the last males, usually worn individuals, fly until the middle of May, barely two months of male activity, but the lives of individual males are bound to be even shorter, something I was referring to in my last post. On the bright side, the females will be still busy nesting for another month

On the odd life cycle of bumblebees

I stopped by the comfrey patch this morning. The comfrey has now been in blossom for a good month. A Small White butterfly was feeding on comfrey, but I couldn't snap her. A ginger queen Bombus pascuorum fed on the blossom. A queen wasp got comfortable on a leaf and basked in the sun, as did some hoverflies. While I watched a couple of Anthophora plumipes males patrolling and feeding, a tiny worker of the tree bumblebee Bombus hypnorum, the first of the year, turned up (above). As I compared the sizes of these two bees – the bumblebee worker was smaller than A. plumipes - I reflected on the different life cycles of these two bee species. A. plumipes, a solitary bee, has males and females, while bumblebees, in addition of males and females (queens), have a worker caste. In bumblebees there are no males for most of the year: A male has a relatively short - if hectic - life. Upon emergence in the summer, he will find a queen and mate with her. The queen will store his sperm and use it to fertilise her eggs the following spring, when she will emerge from overwintering, build a nest and lay fertilised eggs, which will hatch into worker larvae. She will be busy collecting nectar and pollen from early flowering trees and plants to rear these larvae, and once the workers emerge, they will take over from the queen in collecting more nectar and pollen for subsequent eggs, although they won't reproduce themselves.  In the summer, the last batch of eggs of the queen will produce new queens and males, which the workers will help rear. Once they leave the nest, the founder queen and workers will die and the cycle starts again. Wasps, ants, bees, and bumblebees (hymenopterans) share a weird way to determine the sex of the offspring: fertilised eggs become females and unfertilised eggs become males: a system called haplodiploidy.
  Most sexual organisms have two sets of chromosomes: a set they inherit from their mother and another that comes from their father, but as bumblebees and other hymenopterans do not have a dad they just have a single set of chromosomes, the set coming from their mother.
How strange is that? If you think about it, the system means that bumblebee males don’t have dads, they also cannot have sons, only daughters, although they can have grandsons and have granddads. In addition, this arrangement causes strange relationships between the family members. We are equally related to our parents than to our kids – on average – but due to haplodiploidy, bumblebee sisters are more strongly related than they are to their mums. This is because full sisters have received an identical set of chromosomes from their dad, in addition to the set they receive from their mum, which is a mixture from the sets the queen received from her parents.
 This unbalanced genetic relationship between mother-daughters and sisters is thought to underlay the evolution of the worker caste, which do not reproduce, but help their mother to rear their own sisters.
The solitary bee Anthophora plumipes
A wasp? No, the exquisite wasp mimic hoverfly Myothropa florea
This is the real wasp. A queen common wasp 
Hoverfly Syrphus ribesii 
Another basking fly
A queen Bombus pascuorum

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.

Saturday, 21 April 2012

A wet bee on bluebells

Continuing with the rain theme. Here you have a shot I took earlier of a soaking wet Melecta albifrons, during a brief sunny spell. She was still alert enough to offer me her middle leg (a defensive behaviour of bees and bumblebees) when I touched her.

Wednesday, 18 April 2012

Chameleon bug

I took this portrait of a Green Shieldbug during a light shower today. There are three Green Shieldbugs feeding on the spurge, one of them, is the brightest green:
Compare with one I found at the end of March:
A brown, pinkish-purple individual. It is hard to believe they are the same species, but this colour change, which can happens in a few days, is typical of Green Shieldbugs. There is a single generation per year, with green adults emerging at the end of the summer. In November, the Green Shieldbug turns a dark bronze brown, which merges it better with its surroundings during overwintering. Come spring, adults emerge from their overwintering sites and climb over trees and bushes to feed, mate and lay eggs, and they go back to green again. A true chameleon bug!

Tuesday, 17 April 2012

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.

Friday, 13 April 2012

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.

Wednesday, 11 April 2012

The sunny side of the fence

The outside of our garden fence is east facing. Many insects and spiders like to bask on it: even normally ground loving invertebrates climb up on it to get the sun a bit earlier. In the last few days I have been watching (mainly) spiders on the fence early in the morning. The male Nursery Web spider (Pisaura mirabilis) on the top shot, warms up on the side of the fence, in almost the same spot every day.
After warming up yesterday he went down to the weeds at the base of the fence to hunt, and caught a greenbottle fly
A crane fly resting, legs outstretched on the fence.
A male Xysticus cristatus, much darker in tone than the female. This is a ground dwelling crab spider and he was basking about 10 cm from the ground, but it is much easier to spot on the fence.
And an eager male Wolf Spider displaying to the female. Alternatively lifting each palp, trembling and getting closer to her very slowly on tiptoes. She kept tapping the ground with their front legs, and didn't miss a movement. When he got very close, almost touching her, she retreated cautiously, tapping regularly.

Tuesday, 10 April 2012

Red Mason bee male checking out Melecta

A Melecta albifrons male has been feeding lazily on the Erysimum in the afternoon a sunny day.  Clambering over the flowers, not bothering to fly, this cleptoparasitic bee behaves in a very different way to its host: the buzzing, hovering, always alert Anthophora plumipes. Red Mason bee (Osmia rufa) males are patrolling the flowers and they check everything vaguely looking like a Red Mason bee female. With their contact, they scare away females A. plumipes - which I guess feel harassed like they do when their own males jump on them. A male Osmia rufa sees the Melecta and jumps on it. Just a quick contact, presumably chemical cues are checked and if not right, the bee flies away. The Melecta stays on. And when I check the camera, I am thrilled I got the shot!
Melecta albifrons male (photos 26/03/2012). They are handsome bees.

Food for the queen wasp

Queen common wasps (Vespula vulgaris) are very active at the moment. After emerging from their overwintering sites, the queens must build their paper nests, lay eggs and raise the first batch of larvae. They also need to feed themselves. Wasps do not have long tongues and need accessible nectar or other sugary sources. The wasps in my garden love the spurge for that very reason (above), and later in the season they feed on Fennel and Ivy flowers, which have easy reach nectar. They act as pollinators like bees and hoverflies.
They also like ripe fruit and sap from tree trunks.
 The hunting wasps do later in the season (insects, spiders or scavenged meat from sandwiches or carcasses) is not for the adult wasps to eat but for their carnivorous larvae, which will feed on chewed up meat or insects and exude a sugary substance for the adult wasps.

 I do not really know what wasps are up to in my cherry tree (photos above from 28th and 29th of march). They do not visit the flowers but the emerging leaf buds. Are they searching for the nectaries? I doubt it. The photos show they seem interested in the bud covering leaflets. I'd be interested to hear if you know what wasps are getting out of it.

Sunday, 8 April 2012

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.

Sunday, 1 April 2012

New resident male nursery web spider

We have spent much of the day out, sorting out the garden and pottering about the house. In one of the comings and goings I noticed a male nursery web spider (Pisaura mirabilis) sunbathing by our garden gate. By its size I think it is a subadult. I have blogged on this spider before because of its peculiar mating behaviour. The male offers the female a wrapped up prey and plays dead. The females carry their large egg sac in their chelicerae until the spiderlings hatch, but they build a 'nursery web', in the shape of a tent, which they guard and where her spiderlings develop before dispersing. This is an obvious spider that likes to sit in the open with its legs stretched, relying on its camouflage to remain undetected. The photo above, taken by my 9 yr old daughter with her Canon Powershot A495, shows the eye arrangement and striking colour pattern nicely. A beautiful spider, I hope to come across it more often.
A close up of the spider, showing the enlarged palps
Typical posture of Pisaura mirabilis with outstretched pair of front legs