Tuesday, 30 March 2010

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.

Saturday, 27 March 2010

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

Wednesday, 24 March 2010

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.

Tuesday, 23 March 2010

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.

Monday, 22 March 2010

At close range

If a neighbour had casually seen me on my garden this morning, he or she could have rightly thought either that I was out of my mind or that I was practicing some tai-chi. But no, in one of the few sunny spells we had on an otherwise windy, cold morning, an Anthophora plumipes male stopped to sunbathe for a bit longer than usual. It is the longest time I have seen one of these fast high-pitched buzzing bees sitting still. The spot was quite near to the wall where I photographed the male in yesterday's post, possibly the same individual, but the background was much more interesting and I wanted to get a closer picture. Unfortunately, a barrier of lavenders, plum branches and primroses separated me from my subject, so I had to stretch and contort, while supporting myself with one hand on the mud, moving very slowly to take this photo one-handed. I just cannot hold it for a future post, as it is since now my favourite A. plumipes male photo. After a few minutes, the male started looking around nervously, flicking his antennae and, having warmed up, flew away.

Sunday, 21 March 2010

Anthophora plumipes is back!

Yesterday it was the equinox, so it is finally spring. We had a sunny mild day today and from first thing in the morning we've had a couple of Anthophora plumipes males patrolling in the garden. I saw the first male of the year on the 17th of March, but it was too fleeting a sight and he did not stop. Today I managed a few shots during the few seconds one of the males Anthophora stopped to rest on a wall. You can see their forward-pointing middle legs, with the plumes of hairs that give them their name. These bees - as honey bees and bumblebees - are extremely endothermic, that is, they are able to increase their body temperature with respect to their environment and this allows them high activity levels at temperatures where other insects just sunbathe to increase their body temperature. Experiments by Graham Stone and colleagues have studied the ability of A. plumipes to increase their internal temperature. Accordingly, at the 8 degrees in which bees were active this morning, their body temperature is likely to have been around 28oC. The males patrolled constantly in a route around the garden and occasionally stopped to feed in some small Daffodils and Primroses. Males always emerge first from the nest where they were born, followed by the females. This is so because in the long tunnels where females nest, they lay fertilised eggs first (which will become females) and the last ones unfertilised (which will become males) and the bees emerge in reverse order of laying as the last eggs laid are closer to the opening.

Friday, 19 March 2010

The stone dwellers

When repotting a Rosemary I disturbed this Brown Centipede (Lithobius forficatus) which had taken residence at the bottom of the pot. It obviously was taken aback and sat still on the ground for a few moments so I went to grab the camera. Centipedes lose moisture from their bodies quite fast, as they lack an impermeable layer in their integument, so they live in moist environments and are most active at night. For this reason, when exposed from their hiding places under stones, logs (or pots!) Brown Centipedes tend to run away from the light as fast as they can and scuttle under the nearest dark crevice. These common centipedes are carnivorous or detritivorous, feeding on springtails, aphids, flies, spiders, mites, millipedes and molluscs which they immobilise with a venom they inject through fang-like apendages located at the sides of their head.
A close up of the Brown Centipede showing its fattened head with eyes made of a cluster of simple eyes (ocelli), the side of their fangs under its head and their long mobile antenna.
I found this cluster of eggs under a pot last May and a Lithobius next to them. Unfortunately, the little information on eggs I found describes that they lay eggs singly and bury them. I counted 42 eggs here.
Although quick, the Brown centipede is a small animal, up to 3 cm in length, and due to its habits, hard to watch. In contrast the longest centipede can reach over 30 cm. Watch a video of this giant centipede, Scolopendra gigantea, moulting and searching for prey in this post of The Bug Whisperer.

Tuesday, 16 March 2010

Dronefly portrait

I photographed this female dronefly, Eristalis tenax, sunbathing on the Phlomis bush. I like the soft green of the leaves and I played with the depth of field to make the background blurry. If you download the large version of the photo you can see yellow pollen on the fly's legs and some has transferred to the leaves. The only flowers nearby were a few crocuses, so I guess the dronefly had been feeding on them before.

Monday, 15 March 2010

Third bumblebee of the year

A funny title you'd think. Well, I saw my first bumblebee on the 10th, then another on the 13th (both flying over and unidentified) and today, finally I saw one close enough for identification: a Buff-Tailed bumblebee or Bombus terrestris on a pot. Flew quickly away before I could take out my camera (the photo on top is from october 2008) but at least I got a clear ID. It hasn't been particularly sunny today, but it is noticebly milder, around 10 oC, and things are quickly changing in the garden. The Grape Hyacinth flower spears are pushing through the leaves, box buds are bursting. The two last dormant ladybirds on the monkey puzzle have finally broken their long sleep and are moving about.

Wednesday, 10 March 2010

Sweet Snowdrops

I cannot get enough of the sunny weather we are having during March. Today, Honey Bees were foraging on Snowdrops and Crocuses. The one on the top photo was clearly collecting pollen, retreating after entering each bloom and hovering while rubbing their legs together. A full pollen basket is clearly visible.
There were two honey bees at the same time in this crocus.
I also saw my first bumblebee today, flying high over my garden, so I couldn't ID it. I was a bit surprised Anthophora wasn't the first bee of the year.

Monday, 8 March 2010

A glimpse of Spring

We've had a wonderful sunny start of March. Mornings are still frosty, but - compared to the past three long, cold, cloudy and gloomy months - spring seems to be on its way. The first Grape Hyacinths (Muscari racemosum) of the year have opened, joining Snowdrops, Crocuses and Primroses. Today I've been tidying up in the garden. There have been many plant casualties of this unusually cold winter, but the survivors have started to grow, buds are thickening and leaves slowly unfurling.
A Wolf Spider (above) walked on a white wall and settled on an Ivy leaf to sunbathe.
 The pair of 7-spotted ladybirds, of which I wrote before, are still nestled together amongst the spiky leaves of the monkey puzzle tree. They have been there since early November. In contrast, I have seen active ladybirds in more sunny positions in the garden, enjoying the sunshine and hiding again afterwards.
A 7 spot ladybird enjoying the sun
A Bluebottle feeding on an Ivy leaf
Unidentified fly