22-Aug August's Hidden Wonders

When first encountered they often freeze or bob up and down or make a half-hearted attempt to slowly escape. They can easily lose a leg during these interactions leaving it to go on twitching for several minutes after being detached, possibly to confuse predators. Their second pair of legs act as their ears, nose and tongue and you can sometimes see them cleaning them with their other legs.

Compared with the vast number of spiders there is only in the region of twenty-five different harvestmen in Britain. Some of these have shorter legs, others stripes and they can also be several different colours. Their sac-like bodies are usually just 3 to 4 mm. in length but their leg span can often approach 100 mm. They feed on a wide range of small invertebrates e.g. worms, caterpillars, mites, aphids, springtails and small snails but also decomposing vegetable matter.

For this reason they can be found in a very wide range of habitats e.g. trees, hedges, meadows, gardens, walls as well as log piles, garden sheds and compost heaps. Paroligolophus agrestis is one of the most common species.

Harvestmice

They use their prehensile tails to grip one grass stem and then lean over to get hold of another but never jump. At one time they were popular pets having no ‘mousey’ smell and happily living up to 5 years in captivity. As you might expect they eat wheat, barley and oats but can also catch flies with their paws. Due to their diminutive size they easily die of exposure even after heavy thunderstorms. As winter approaches they leave these aerial nests and tend to move to drier ground, building moss-filled nests perhaps in hedges or grass tussocks to get them through the winter.

Dormice, another attractive rodent, are a little more common in London, still holding on in woods with a dense understorey in the Bromley area. They also build aerial nests and are particularly fond of building them in regularly coppiced hazelwoods. Their nests are often quite low down in among a tangled mass of branches and bramble where leaves may have collected covering the nest itself. Sometimes people claim to hear them snoring in such situations. They are famously lethargic as Lewis Carroll reminds us in Alice in Wonderland. They hibernate for half the year from October to March and sometimes even longer. During this period their temperature and blood sugar falls and their muscles tighten and become more rigid. This explains why they were able to be rolled across a table-top without waking up and also why sometimes boys were known to keep them coiled up in their pickets. If woken up they are still quite lethargic for some time.

In the nineteenth century they were common in places such as Blackheath, Harrow, Perivale and Coulsdon but are now rarely seen, being nocturnal. Their presence is sometimes betrayed by honeysuckle that has been stripped although other creatures can also be responsible for that. A more telling indicator are holes in hazelnuts that have very clean edges with no jagged bits. They have no prehensile tail like a harvestmouse but are agile and particularly good jumpers, using their tails for balance. Their drowsiness led to them being called dozing mice or sleepers and similar to harvestmice they were at one time kept as pets.

Caterpillars

Butterfly caterpillars tend to be small and either green or black but moth caterpillars are often considerably bigger and more colourful, some even reaching eight centimetres in length. Generally they feed at night and hide away near their food plant during the day but others such as Script and Ghost moths feed underground so we are far less likely to ever encounter them. If looking for some of the more interesting species it is worth examining favourite food plants such as oak, poplar, willow, beech, hawthorn, blackthorn and nettles. Garden plants are also surprisingly popular, even alien plants such as Buddleia.

Many species rely on camouflage to protect them from predators but others prefer bright warning colours or long poisonous hairs. Some that have spent the summer feeding in tree canopies now descend the trunk of the tree to pupate in the ground. On these journeys we often notice them either on a trunk or crossing paths or pavements.

Among the largest and most noticeable are the Hawkmoth caterpillars. In London there are three that might be seen, the Lime hawkmoth on lime trees and the Eyed and Poplar hawkmoths on poplars or willows. The Lime hawkmoth Mimas tiliae (60 mm.) has caterpillars that have even been called beautiful. They have diagonal yellow stripes and red dots or “eyes” with white pupils set on a lime-green background although it does turn more of a purple-brown approaching pupation.

The Eyed hawkmoth Smerinthus ocellata (80 mm.) caterpillar is similar but more of a bluish-green and has paler yellowish-green stripes and the Poplar hawkmoth Laothoe populi (65 mm.) is again similar but smaller with a yellow tail or horn compared with the darker horns of the other two. Whilst looking on poplars it is also worth looking out for another unusual caterpillar, the Poplar Kitten Furcula bifida (40 mm.) It is bright green with a purple saddle but noteworthy for its two long elegant tails.

One of the caterpillars most likely to be seen this month is the black and orange-yellow striped Cinnabar moth Tyria jacobaeae (30 mm.) defoliating ragworts. The centre of London is not a place you would ordinarily look for caterpillars but two you might see are the Sycamore and the Vapourer.

The Sycamore Acronicta aceris (40 mm.) feeds on sycamore but also on horsechestnut and plane trees all of which are common centrally. It is covered in long, yellow or orange hairs and is occasionally noticed curled up in a U-shape on pavements. The Vapourer Orgyia antiqua (35 mm.) also feeds on plane trees. It has a row of yellow brush-like tufts along its back. Like so many other hairy caterpillars these can cause a rash if handled. Other caterpillars with tufts (Tussock moths) include the Pale Tussock moth Calliteara pudibunda (40 mm.) which were so common in hop fields prior to insecticides they were known as Hop dogs by the pickers.

Two other caterpillars naturalists always hope to encounter are the bizarrely-shaped Lobster moth and the equally extraordinary Puss moth. The Lobster moth Stauropus fagi (60 mm) starts off life looking like an ant and ends up similar-looking to a reddish-brown lobster. It may possibly still be found on beech trees in Epping forest. The Puss moth Cerula vinula (65 mm.) conveniently feeds on the upper sides of poplar and willow leaves but inconveniently holds on very tightly if the tree is shaken so much so collectors used to tie sticks together to try and knock them off. It is a bright green caterpillar with a purplish saddle. If alarmed it swells in size producing a scarlet collar, two menacing false eyes and two bright red waving filaments. If this is not enough to deter its persecutor it can also eject a spray of formic acid from the back of its head.

A caterpillar much more easily found at this time of year is the Campion moth Sideridis rivularis (35 mm.). If the ripe fruit capsules of White campion are examined, inside there is often a small “pot” of seeds waiting to spill out but occasionally instead there is a large caterpillar sequestering there during the day, presumably having eaten the capsule’s contents.

Sometimes when a leaf is overturned there is a collection of what look like green and black moth or butterfly caterpillars which all raise themselves up vertically in an “alarm position” to deter predators. If examined more closely they have more than four pairs of false legs or prolegs typical of moths; they will all be sawfly larvae. We often don’t get to see butterfly chrysalises or moth cocoons being constructed or even find them as they are often dark in colour, hidden away or even buried. The silvery paper cocoons of Burnet moths attached to grass stems on good downland are a notable exception.