28-June London’s Eight-Legged Acrobats & Silk-Spinning Caterpillars

Spitting spiders (Scytodidae) have just one representative in London Scytodes thoracica which can be found in our homes. In the wild it used to be found under stones and among deep vegetation. It is famous for spitting thread laced with gum and poison to cover its victims till they are rooted to the spot. Having just small fangs it then waits to bite a vulnerable spot such as a wing or a leg. Although nocturnal, if seen it is easy to recognise as unusually its carapace (i.e. head and thorax joined) and abdomen are more or less similar in size and it is yellow-brown and black.

Another family of spiders found in our houses are the cellar spiders (Pholicida). One typical species of this group found in London is Pholcus phalangioides which looks for all the world like a daddy long-legs except for the fact it is usually found sitting in the centre of an open tangle of threads like other cellar spiders. If some small unwanted creature accidentally stumbles into the web it is capable of gyrating so fast it becomes blurred. This violent reaction is meant to either frighten away the intruder or dislodge it. Another family of spiders that can vibrate are the buzzing spiders (Anyphaenidae), the males of which sit on leaves vibrating to attract females. Anyphaena accentuata is one of the species that could well be in every wood in London. It is pale yellow to pinkish brown with two variable black marks on its abdomen.

Jumping spiders (Salticidae) are amongst the most rewarding to watch. They are sometimes noticed on walls and are not above jumping onto an inquisitive finger. They tend to have four of their eyes that are considerably larger than the rest and look a little like headlights. Not just this but they have a habit of standing and staring at us, their eyes not just moving from one side to another but sometimes even changing colour. Once seen it is worth waiting for the “jump” which can be up to twenty times the spider’s body length. However, in the Zebra spider Salticus scenicus, a species often found in houses with zebra-like markings, the “jump” will be little more than a centimetre.

Comb-footed spiders (Theridiidae) get their name from the comb-like bristles at the end of their hind legs which they use to throw silk onto their prey. These combs we cannot see but we can see their tangled webs of random construction which is a typical feature of the family and is why they are also called tangle-web spiders. The webs often have a small cup-shaped retreat at their edge where the spider sits and waits. They tend to be small, glossy often attractively coloured spiders with round bodies and short legs. Theridion sisyphium, the Mothercare spider, is one well-known species with white lines across its abdomen which is found in bushes and low vegetation. Like other comb-footed spiders it wraps up its prey and leaves it fixed to the web but is better known for feeding its young with spider milk.

Nursery web spiders (Pisauridae) are also known for looking after their young in this case constructing a “nursery tent” for their spiderlings then sitting beside it to protect them. Pisaura mirabilis is one species that may be seen in woods and on heaths. It is a large spider (10-15 mm) with conspicuous tear marks beside its eyes and a yellow line down its back. The male is famous for presenting its mate with a silk-wrapped corpse then waiting for her to start to eat it before copulating with her.

The webs of funnel web spiders can look a little like sheets of silk with a central funnel at the end of which is often a dangerous-looking spider. These sheet webs are seen on bushes and low vegetation and are held in place by a patchwork of other threads. One largish species the Labyrinth spider Agalena labyrinthica (12 mm) has been found on Hampstead heath. If an insect walks across its web or a grasshopper lands on it Agalena will dash out of its funnel and bite its prey. Unlike many other spiders it will often remain with its fangs in its prey and continue to suck its body fluids till all that is left is a husk.

The corpse is then often just left discarded at the edge of the web. Another unusual feature of this spider is that the female allows the male to cohabit with her. However, some time after copulation she will leave him and her “labyrinth” to build a silken cocoon to house her hundred or more eggs. She then protects them till they hatch and then she dies.

Caterpillars

. Tussock moth caterpillars have distinctive toothbrush-style tufts of hair along their backs and other caterpillars have bright colours, spines or horns which can help to identify them. Others stand out because they are either very large, live in silken tents or perhaps just hang from trees on silk threads.

The eggs of some of our butterflies e.g. Brimstone, Orange tip, Green hairstreak, Peacock and Painted lady are all now hatching. Several of the blues, the Comma and the Purple hairstreak may well have hatched a little earlier. The caterpillars of some skippers, the Ringlet and Marbled white can all be found in several different months of the year and butterflies that have more than one brood e.g. whites, Adonis blue, Holly blue, Speckled wood and Red admiral are all seen in more than one season. Compared with moth caterpillars our butterfly caterpillars are not usually particularly colourful but some, such as the blues, do have very beautiful, highly sculpted eggs. Many of our butterfly caterpillars are small, green with thin lines of colour usually either yellow, reddish or purple.

A row of tufts along the back could indicate a Red admiral, Small tortoiseshell, Peacock or Comma. Any found on buckthorn are likely to be Brimstone butterflies as they have such a restricted diet.

It is easy enough to find caterpillars of white butterflies on cabbages in gardens. Wimbledon common is a good place to see geometers on the oak trees either looping when disturbed or hanging on silk threads. Sometimes notices are put up where there are silken tents filled with such gregarious caterpillars as the Brown tail.

These are to warn people that if these caterpillars are touched they can inflict serious skin rashes. More recently in London there have been notices about the Oak processionary moth which has long, poisonous, white hairs but is better known for its habit of abandoning old nests and all the caterpillars moving in a procession, nose to tail to find a better place to feed and build a new silk tent.