Little pole vaulters

Pottering around in the conservatory the other day I noticed a large springtail walking on the floor. When I say 'large' of course, it is in relative terms as the animal was around half a centimetre long. Springtails, or Collembolans are small wingless hexapods less than 1 centimetre in length, some - one of the smallest insects- less than half a millimetre. Due to their small size they often remain unnoticed, until they jump. And jump they can: springtails can cover many times (I have read up to 20 times) their own length in a fraction of a second. Their name gives away the mechanism they use to jump. They have a prolongation of their abdomen (a forked 'tail' or furcula) which is normally folded under the insect and secured in place with a 'catch'. On being disturbed, the springtail releases the catch and the 'tail' pushes fast against the substrate, catapulting the springtail into the air away from danger.
 My conservatory springtail proved easy to identify thanks to a very exhuberant mane by WAB member Jason Green as Orchesella villosa. Going back to old photos I found one where a couple of individuals of the same species enjoy the underside of a fallen apple with some slugs and woodlice like a group of friends that have found paradise.

Many resources on springtails state that their relationships with insects is unclear, as some research showed they might be more related to crustaceans. To clarify this debate, a recent paper by Regier and collaborators, based on a phylogeny of 62 genes showed conclusively that collembolans are indeed hexapods and more closely related to insects.
More information
A very informative account on Collembollans by Steve Hopkin here.
Collembola.org by Frans Janssens.
Regier, J.C. et al. (2010) Arthropod relationships revealed by phylogenomic analysis of nuclear protein-coding sequences. Nature, 463:1079-1083. here.

Woodlice hunting spiders

I occasionally come across Woodlice hunting spiders (Dysdera) in their silky day retreats when moving pots. These relatively large and brightly coloured spiders are strongly photophobic and run away from the light as fast as they can looking like they are dragging their bodies on the ground as they go. I haven't managed to take a decent photo of these spiders outside my plastic bug container (above) because of they dislike of lights. Dysdera spiders have traditionally been considered specialists on hunting woodlice. They have long, thin and highly mobile forward facing chelicerae (fangs) which it uses as pincers, catching the woodlice and then piercing the underside not as armoured side of woodlice. They are known to be able to deliver a painful bite if handled by brave humans. As they hunt during the night, when they come out of their retreats, their diet is difficult to study in the wild and there is some debate as to how specialised on woodlice these spiders are. In captivity, they are not fussy eaters, and feed on a variety of invertebrates, they seem to say no to nothing! What is certain is that they do eat woodlice, and the few times that they have been found in the wild with a captured woodlice suggests they might be an important part of their diet. Dysdera spiderlings raised on woodlice alone or combined with flies grew faster than those raised only on flies, sugesting some degree of physiological specialisation. In addition, not many spiders like woodlice - one of the few is the daddy long legs spider Pholcus- and here is a photo of it.

A Pholcus with its woodlouse prey in the kitchen

More information

S.D. Pollard, R.R. Jackson, A. van Olphen and M.W. Robertson (1995) Does Dysdera crocata (Araneae: Dysderidae) prefer woodlice as prey? Ethology, Ecolgy & Evolution 7:121-275. here.

J. A. L. Cooke (1965) A Contribution to the Biology of the British Spiders belonging to the Genus Dysdera. Oikos, Vol. 16:20-25. here.

Milan Rezac and Stano Pekar (2007) Evidence for woodlice-specialization in Dysdera spiders: behavioural versus developmental approaches. Physiological Entomology 32: 367-371. here.

Bug overload!

These days I find it difficult to settle on a topic for the blog. We have gone from long bug-poor weeks of indoor seclusion through the long harsh winter to a month of March when things seem to happen too quickly. So I am writing posts more alike to my nature notebook, which, by the way, was the original intention when I started. We had a lovely sunny, mild day today and I pottered about in the garden bug-watching and took a couple of local walks. Even when doing the shopping I came across bugs worth posting about. What to choose? I just can't.

Small Tortoiseshell on willow

A male Anthophora plumipes hovering

The morning started by my discovery of a bug magnet in a neighbours garden: a flowering willow. The large bush was teeming with bumblebees, all of the ones I could see were Bombus terrestris. A Small Tortoiseshell, the first one this year, feed in the catkins and several Anthophora plumipes males were hovering around ramming every now and then both the butterfly and the bumblebees. I took a few pictures but I wasn't close enough for good ones. I had to stop myself from picking up the binoculars, though, to watch the activity at close range. Nectar-feeding insects prefer to visit sources where flowers are in large masses, so that they save energy looking for the next source. Willows in early spring provide a large number of flowers where typically there are not many other species flowering, so they are sought after my many bees and bumblebees.

 A brimstone passed by flying over the gardens. This is my typical brimstone sighting, early spring, fluttering past, never stopping and I rarely see them again the rest of the year. A frustrating butterfly! The following photos illustrate other sightings.

A beautiful Harlequin sunbathing

A couple of mating 7 spot ladybirds

Baby millipedes found clinging to an old conker

Bug watching day

Around midday, a giddy Peacock - my first butterfly for 2010 - fluttered around the garden until it decided after a good while to settle and enjoy a sun spell on one of my first ground windowsills - which as you can see badly needs painting!. Peacock was also the last butterfly I saw in 2009 (29/10). Almost five months without butterflies is far too long!
 Then, I watched more Anthophora plumipes in the garden. I had seen one of the males patrolling the Tet-a-tet daffodils, but this morning a male actually fed from several of them.

I managed this shot of the male, tongue extended in preparation for landing on a Daffodil.

The male (or males) were feeding today on Muscari, Pulmoraria and the Daffodils. Often they dart to a clump of flowers, hover briefly to inspect them and dash away before I have the chance to press the shutter. Later in my street another A. plumipes was visiting pansies and cultivated primroses (both of them first time I see them visit). So that adds three more flowers to the plants for your 'Flower Bee Garden'.

Seven spot ladybirds and a harlequin were active in the garden, and a queen Bombus terrestris queen visited the garden looking for nesting sites with their characteristic low wandering flight. Two other unidentified bumbles flew overhead.

Bombus hypnorum here to stay

Coming out of work I see the first Bombus hypnorum of the year: a dying, squished female, possibly a queen. B. hypnorum, or the tree bumblebee is a newcomer in the UK. It appears to have arrived on its own steam, possibly an inseminated queen crossed the channel around the turn of the century. The first specimen was collected in the New Forest in July 2001. In mainland Europe it is a species closely associated to human habitats. It is a species quite easy to identify due to its striking coloration: ginger thorax and black abdomen with a white tail. It is a good size bumblebee, similar to B. terrestris.
 In July 2005 I reported the first B. hypnorum in Hull and I have recorded it every year since. In the UK B. hypnorum has expanded steadily through most of England - click here for the 2009 records - and it appears that its status as a British bumblebee is consolidated.
 It nests in trees, often in nest-boxes and also in roofs and while foraging, it has a preference for high flowers. The bumblebee is found from March until September. These are the flowers I have observed it foraging:
March: Mahonia
April: Cherry
May: Rowan, Comfrey, Cotoneaster horizontalis
June: Bramble, Deutzia, Cotoneaster, Comfrey, Angelica, Hebe, Snowberry bush
July: Teasel, Cotoneaster, Lavender, Hebe
August: Snowberry bush, Buddleia
September: Ceanothus

The first recorded B. hypnorum in Hull

The entrance to a B. hypnorum nest in a nest box. Flies appear to be always at the entrance.

BWARS gallery page for B. hypnorum here. You can also send your records to BWARS.

First B. hypnorum record by Dave Goulson and Paul Williams here.