Thursday, 28 June 2012

Tree sculptures and lesser stag beetles

In the last three weeks, I have been coming across Lesser Stag Beetles (Dorcus parallelipipedus) dead on the pavements in my street. June and July are peak emergence time for these dark, flattened beetles. Today we found 10 squished ones and a live one next to a chestnut tree stump, is this were they were coming from? I got the impression that the beetles might have been seeking shelter under the wheels of a car parked next to the stump, and they were inadvertently squashed every time the car moved. This tree stump used to be a tree sculpture (here for a photo, yes, the car behind is the beetle squasher!). Old trees that have got too big are partially felled in our neighborhood to avoid subsidence and then carved into statues. The dry dead wood soon becomes peppered with many tiny beetle holes, which are taken over by little wasps to nest, accompanied by their suit of parasitoids. The sculpture was taken down last year as it had started to rot and become unstable. The remaining stump was as soft as crumble. When I looked into it today, many large exit holes were visible on the surface. I dug a bit into the rotting wood with a stick and it didn't take long to find a Lesser Stag Beetle larvae. They have a large head, strong dark mandibles to chew the rotting wood and a c-shaped body curled underneath. The larva was very active, it turned round and quickly moved away hiding into the wood. Millipedes, woodlice and earthworms shared the dead wood with the beetle larva.
The collection of dead Lesser stag Beetles. The one on the bottom left-hand side is a large male with impressive jaws. There is huge variation in size amongst individuals.
A close up of the stump with exit holes.
An overview of the Chestnut tree stump
A side view of the young larva
Lesser Stag Beetle larvae take over two years to develop, and several stages may coexist in the same stump. Adults also may live several years, so it is a shame so many are dead, but this stump probably holds many tens of larvae and many adults have probably already dispersed successfully after emergence. 

Sunday, 24 June 2012

Neriene montana egg guarding

The contrasting red background of a kids wheelbarrow, made it easy to spot the egg sac of this Neriene montana female. The yellow eggs are visible through the loose, gauze-like silk wrapping of the egg sac. The female hangs upside down on her hammock web by the egg sac. She may possibly be able to lay more egg batches, as the female lives up to 7 months. Although egg guarding has not been reported in many money spiders and I could find very little on the reproductive behavior of this species, this photo confirms that the eggs may be laid very close to the web and will undoubtedly benefit from the female being nearby.

Tuesday, 19 June 2012

Six or eight legged bug army fighting aphids

 Neat rows of black aphids suck the sap of one of the stems of a Lesser Knapweed in the garden. This morning, I notice a hoverfly, Syrphus ribesii, around, she lands near them, flies straight to the top of the aphid group and curves her swollen, pointy abdomen towards the branch. She is egg laying, notice two elongated white eggs near her in the top shot. She came back again to lay more eggs near the same spot. Hoverfly larvae feeds voraciously on aphids and female hoverflies choose the best spots to maximise the chances of their offpring thriving. Aphids populations are booming now and several groups of insects and spiders exploit them as their predators and parasites, as illustrated in the following shots.
A hoverfly larvae eating an aphid in the roses.
A parasitic wasp approaches a group of elder aphids. She will inject an egg into the body of an aphid and the wasp larvae will develop inside it.
This other wasp is laying eggs inside the aphids.
Adult 7 spot ladybird eating an aphid on rose.
Araneus diadematus spiderling on its web with a captured winged aphid
Late instar harlequin larvae with aphid
Philodromus spider with prey
And a jumping spider
A mirid flower bug nymph, Anthocoris sp. sucking the juices of the aphid in much the same way the aphid does it to plants.

Saturday, 16 June 2012

Girl power: sex and parthenogenesis in Vine Weevils

ResearchBlogging.orgPrecariously perched on a young oak branch, a Black Vine weevil, Otiorhynchus sulcatus, the first of the year. I am really not looking forward to seeing them, but they have an intriguing life cycle, which is key to their success. The Black Vine weevil is a generalist feeder which in the early 19th century was only known in a small area in Central Europe and since then has expanded to much of the world aided by human activities and has become a pest of a range of agricultural and horticultural plants, despite being a flightless, sluggish insect.
 The remarkable thing about them is that all Black Vine Weevils are female. A weevil does not need to find a partner to mate before reproducing, she just emerges from the soil, stumbles to the next suitable patch and lay eggs. The next generation of daughters will be genetically identical to their mum, forming natural clones. Parthenogenetic lineages in general are good colonisers, and expand their population ranges more easily than their sexual relatives. Individuals might disperse the same distance during their lives, but in the parthenogenetic species a single individual can successfully colonise a new patch and establish a new population, while the sexual species needs at least two individuals of different sex - or a fertilised female - and then has to cope with the disadvantages of inbreeding if it succeeds. Most parthenogenetic insect species are flightless, which suggests that parthenogenesis is more advantageous if the insect is naturally a poor disperser.
But there is another card up the weevil sleeve. These beetles are triploids, instead of having the usual two sets of chromosomes (that is, being diploids, like us) they have three. Polyploids are often larger than diploids and may enjoy further ecological benefits such as more resistance to the cold or wider ecological tolerances. Ecologically, parthenogenetic weevils have moved much from their origins in the moist valleys of the Alps, and are now able to persist even indoors, munching the roots of plant pots.
They might not be the most attractive insects, but these weevil story of success shows that appearances can be deceiving and that, sometimes, girls rule.

More information

Lundmark M (2010). Otiorhynchus sulcatus, an autopolyploid general-purpose genotype species? Hereditas, 147 (6), 278-82 PMID: 21166797

Friday, 15 June 2012

A Strawberry Seed Beetle

ResearchBlogging.orgGiven that the weather is so damp and cold I am seeing very few insects these days other than bumblebees. At least I have plenty of time to tidy up my ever growing photo library! While going through my ground beetle photos, I thought I would share this shot of  Harpalus rufipes, a common species that I have even found inside the house. The species is quite distinctive with its orange legs and its wings covered on very fine hairs - giving the elythra a matt feel when compared with head and front of the thorax. This is an omnivorous beetle: it will predate small invertebrates but also feeds on seeds, and gets its English name from the damage it inflicts on strawberries. The species is biennial. It breeds in August and the adults overwinter and overlap with the larvae. The larvae dig deep vertical where they cache seeds, which I thought it is pretty cool behaviour for a beetle. As other common European invertebrates, it was introduced in North America before 1937.

More information

Loughridge, A., & Luff, M. (1983). Aphid Predation by Harpalus rufipes (Degeer) (Coleoptera: Carabidae) in the Laboratory and Field. The Journal of Applied Ecology, 20 (2) DOI: 10.2307/2403519

Hartke, A., Drummond, F., & Liebman, M. (1998). Seed Feeding, Seed Caching, and Burrowing Behaviors of Harpalus rufipes De Geer Larvae (Coleoptera: Carabidae) in the Maine Potato Agroecosystem. Biological Control, 13 (2), 91-100 DOI: 10.1006/bcon.1998.0645

Thursday, 14 June 2012

Never hold a Black Clock in your mouth

I found a squished ground beetle on the pavement today, Pterostichus madidus, and I thought I would share with you some photos from last year of a very alive individual of this species . Curiously this carabid beetle has a curious English common name: the Black Clock. According to the book Bugs Britannica, by Marren and Mabey 'clock' was a word in widespread use to mean any big buzzing insect. As many carabids, however, this is a fast, non-flying nocturnal predatory beetle which runs to hide quickly when uncovered. This one was found under a grass tussock in the garden. Look at his sharp jaws!
 Ground beetles have glands at the end of the abdomen that produce defensive, foul tasting and caustic secretions. I must quote here an incident involving ground beetles described by Charles Darwin
I must tell you what happened to me on the banks of the Cam in my early entomological days; under a piece of bark I found two carabi (I forget which) & caught one in each hand, when lo & behold I saw a sacred Panagæus crux major; I could not bear to give up either of my Carabi, & to lose Panagæus was out of the question, so that in despair I gently seized one of the carabi between my teeth, when to my unspeakable disgust & pain the little inconsiderate beast squirted his acid down my throat & I lost both Carabi & Panagæus!
The pains beetle collectors went through to capture priced ground beetles! You can admire the handsome Crucifix Ground Beetle (Panagaeus cruxmajor), also known as 'Darwin's lost beetle' here. Unfortunately, due to collecting and habitat degradation, this species, formerly widespread, is now just know from three populations in the UK.
But back to my beetle, I managed to take some shots of the individual scurrying off for cover on the soil, and then I decided to capture it and give it a session in the white bowl. I think the following two photos show the pros and cons of the natural versus the white background.

Pterostichus madidus, 12 May 2012
More information
Charles Darwin letter to Leonard Jenyns in the Darwin Correspondence project.
Crucifix ground beetle (Panagaeus cruxmajor) UKBAP plan.

Monday, 11 June 2012

Figwort Weevils

I found this Figwort Weevil, Cionus scrophulariae, individual near a mating pair on Buddleia. I used to see them on Figwort, but they also feed on Mullein and other plant species, usually near the flower buds or young shoot tips of the plants. The larvae is unmistakable: it looks like a slimy yellow-green blob with a black head, and is found on the same places that adult frequent.
Mating pair
Two larvae and evidence of their eating the Figwort
Another mating pair

Sunday, 10 June 2012

A morning beewatching

A warm morning of sunny spells, bees come out en force. A Cuckoo bumblebee, possibly a male Bombus vestalis (above), a cleptoparasite of Bombus terrestris fed on the Erysimum Bowles Mauve. Bombus pratorum workers and males are feeding on many flowers, Centaurea montana, Chives and Herb Robert, surprisingly also Foxgloves and also nectar robbing the Comfrey.
A couple of queen bumblebees, Tree (above) and Buff Tailed bumblebees feed together on the patch of Red Valerian for a long time.
On the Oxeye Daisies, a Lasioglossum sp.
The first leaf-cutter bee, Megachile willughbiella, of the year feeding on Erysimum. I also saw it on the geraniums.
 Wall Rocked receives a visit of a very worn Andrena
The new Osmia caerulescens are now everywhere. The males have been checking the bee post. In the next shot, a male stretches its tongue, amazingly long. No surprise its preference for Sage and Lamium maculatum in the garden.
This female sunbathing next to the Sage shows why they are called Blue Mason Bees
The summer bees overlap on early June with the last of the spring bees. An Anthophora plumipes female was briefly feeding also in the amazingly popular Erysimum. Finally, Red Mason Bees, Osmia rufa were abundant. Overall 11 species, not counting honeybees. A wonderful morning bee watching!

Wednesday, 6 June 2012

The Panther Spider

Upon removing a pot from a wall this morning, I exposed a beautiful adult female Mouse Spider,  Scotophaeus blackwalli, her abdomen full and glistening. Although initially flighty, she eventually settled on the white bowl and allowed me to take her portrait. In his classic book 'The World of Spiders', packed full of interesting observations on the behaviour and natural history of British Spiders, W.S. Bristowe described these nocturnal spiders and their relatives as the 'panthers or pumas of the invertebrate world'. However, a few lines later he pushed aside their hunting habits and instead gave this spider a much less impressive common name:
If an English name were needed for our only domestic species, which is found rarely away from man's buildings in hollow trees, it would be appropriate to call her the Mouse Spider on account of her glossy grey abdomen. But she can be a very fierce mouse. She reaches 11 mm. and has short brown legs and a rather narrow head.
He goes on to describe its ability to subsist without water for months and its prowling behaviour 'at night on walls and ceilings in search of prey, retiring behind pictures or onto crevices in walls during the hours of daylight.' He must have kept this spider in captivity and observed it carefully and he goes on to describe its encounters with prey and its short mating behaviour. He describes to have observed two cases of mating in July. And it is at this time of year that adult specimens can commonly be found.

More information
Bristowe, W.S. 1958 The World of Spiders. Collins New Naturalist Series, London. 304 pp.