Sunday, 14 September 2014

Motherly candy-striped spiders

I find maternal behaviour of spiders fascinating, and I keep an eye for it whenever the opportunity arises. When repotting my gingko bonsai on the 2nd of September, I noticed a couple of rolled leaves. They contained web shelters of Candy Striped Spiders Enoplognatha ovata/latimana. One of them had a female with her egg sac, the other already contained spiderlings (above). I checked today again, both females were guarding their spiderlings. The first one approached the entrance of her leaf to check what was causing the disturbance, the spiderlings clustering together like Araneus spiderling balls. The spiderlings have been in one of the nests for almost two weeks. Will the presence of their mother increase their chances of survival? will the mother feed during this time? In the related genus Theridion (Enoplognatha ovata was previoulsy called Theridion ovatum) the presence of the mother guarding the egg sac appears necessary for egg survival (although there were some loses due to parasitism from a tiny wasp). The mother not only sits near the egg sac, attached to her by a silk thread, but she is on the alert, and will move the egg sac to the centre of the web when predators are nearby. Unguarded egg sacs are rapidly predated by insects (ants, earwigs) and other spiders. And what about the spiderlings? what do they have to gain from their mother's care? In the Happy Face Spider, Theridion grallator, the female loosens the egg sac allowing the emergence of the spiderlings, and then captures prey for her brood. The spiderlings are under the female care up to three months, until they disperse and feed on their own. The female might produce another egg sac if the first one is lost, but she will die by the end of September early October. The spiderlings will disperse and overwinter near the ground.
One of the females, in close contact with her egg sac (2/9/14)

More information

Friday, 12 September 2014

Land flatworm

Some posts take a long time to come out. This one in particular has been on the shelf for a long time. The reason? I wasn't sure of the identity of the animal for a while. I found it under a stone on the 29th of September 2012. A small, shiny white long thing, looking like a piece of root, but then it moved! What on earth was it? I picked it up and placed it on the white bowl, where its paleness didn't contrast as brutally with the background. A very stretchy animal, with no rings or setae: cannot be a nematode or an annelid... a flatworm? I got excited, a land flatworm, wow!, I didn't know we got these in gardens. Then I thought, wait a minute, isn't there an invasive land flatworm? I researched the topic. Yes, there are three species of native British land planarians...and at the turn of the XXI century 10 introduced species. After some inquiries it turned up mine was probably one of the native species, Microplana scharffi. Thank you to Christian Owen in iSpot who identified it for me.
The flatworm with its head up

Elephant hawkmoth and caterpillar eyespots

While visiting a farm in the Peak District, we stumbled with this awesome mini beast: a fully grown Elephant Hawkmoth caterpillar. I had been wanting to see this caterpillar for a long time. Knowing that they like willowherbs I had often look for them when I saw a drift of rosebay willowherb. But not this time, somehow, its dark colour made it stand up against the green foliage. She was hanging upside down from the underside of a rosebay willowherb leaf, on a plant growing by a hedge.
 While handling it it adopted all the postures this caterpillar is known for, suggesting either an elephant, when the caterpillar is fully extended, or a snake, when the caterpillar is disturbed and it raises its front, while retracting its head.
 A 'snake' resemblance is a recurrent theme in various large caterpillars from several families, and it has been suggested that this way the caterpillars gain protention from birds, wary of snakes, which are startled when the caterpillar moves its head and the eyes are exposed on the thickened anterior end.
 A Canadian team formed by Thomas Hossie and Thomas Sherrat carried out an interesting set of experiments using pastry caterpillars, which they exposed to natural predation by placing them in branches in the wild. They used pastry caterpillars coloured with food dye with or without eyespots with or without defensive posture ('snake') and with or without countershading.Their results suggested that the presence of eyespots and the raised position might deter birds from eating the caterpillars and countershading and the position of the eyespots in the thickened anterior end has a protective effect too. But don't rely on me telling you, as you can read it from Hossie's himself in his blog Caterpillar Eyespots.
A close up of the eyespots.
The 'elephant' pose.
and the 'snake' pose
another angle of the snake pose
And of the elephant pose.
The happy caterpillar munching away on its new home.

Sunday, 31 August 2014

Three bright characters for the end of August

Some invertebrates appear as heralds of autumn, and today three striking ones were present in the garden. Migrant Hawkers have been around for a while, forming loose swarms that hunt between 2 and 8 m high, often well away from water. In the cooler, shorter days of late summer it becomes easier to come across sunbathing ones, perched on a branch, often more than one near each other. I flushed this male a few times as I went about in the garden, until I finally spotted him hanging from its perch. I got so close taking the macro above that I could have kissed him.
A single Red Admiral was also about, alternating between feeding in the buddleia and basking on a brick wall. During sunny spells she closed its wings, while during passing clouds she revealed its fresh, amazingly marked wings to their full splendor. This was a beautifully marked individual, the small, delicate blue markings on the edge of its wings very apparent.

I used the flash to counteract the sunshine and reveal the intricate patterning of the underwings, which can make the butterfly well camouflaged.
This garden spider, Araneus diadematus, is one of the largest in the garden, she hangs her web on the side of the rubbish bin, and has her retreat under the rim. Given the size of this species, detailed inspection of the epigyne is possible without even disturbing the spider (click on the photo to see it).

Thursday, 28 August 2014

Common Darters

There were at least two male Common Darters, Sympetrum striolatum, around the wildlife garden pond today. If you move slowly, they are great posers and allow very close approximation. Their faces are locked into a perpetual smiling grimace, adding to their charm. If you watch them from a close distance,  you'll notice that they are constantly flicking their heads around, looking for insects flying overhead. If a suitable one is detected, they dart off, returning to their perch to eat their prey.

The ever smiling darter
A short clip of the darter watching for prey.