WETLANDS - OTHER INVERTEBRATES

Dozens of invertebrate species besides dragonflies are found in water and plenty more can be seen close by. A handful are shown under Ponds in the Garden section of this website; here are a few others.

Mayflies have a bizarre life cycle, living in the water for two years as nymphs then emerging as adults in swarms purely as mating machines who die within a day.

Like Odonata, they are suited best by clean water and the commonest is Ephemera danica (body length 25mm), whose larvae feed on algae and debris. The winged adults which emerge from the water are called duns and are dull in colour because not fully mature - they soon moult after finding cover in nearby vegetation (nettles, hedges and so on), thereby reaching the full, shiny adult state.

Much smaller, and with two 'tails' rather than three, is Centroptilum luteolum (8mm),which rather cocks a snook at its title by being found from April to October.

There are about 200 different types of Caddis Fly in Britain. They tend to be brown or black and intriguingly some live as nymphs by covering themselves in a portable casing of debris, such as plant material or sand grains, drawn from the bottom of the river or pond. These generally are not predatory, unlike the free movers. Most of the group, like Mayflies, do not feed after emerging as adults.

Alder Flies (Sialis lutaria, 15mm) are related to Lacewings and their larvae are predators living in still or slow-moving water. The adults, which are weak fliers, emerge in large numbers in late spring, eating little and laying eggs on aquatic plants or any flora overhanging water, such as trees. The larvae fall in once they have hatched.

The Raft Spider (Dolomedes fimbriatus, 20mm) is much commoner than its relative from the Pisauridae family, Dolomedes plantarius, which is endangered and found only in East Anglia. Both species require swampy conditions and are large and robust, capable of catching sizeable prey including damselflies and small fish. The latter are attracted to the surface by the spider vibrating the water with the front legs.

Females can lay up to 1,000 eggs in sacs which are ferried about underneath the abdomen. Spiderlings can be found in shrubs or trees rather than in the water.

Not many Hymenoptera are based entirely around wetlands because of the threat water poses to their nest sites. Two notable exceptions are the bees Macropis europaea (10mm) and Hylaeus pectoralis (7mm), each of which is nationally scarce.

Macropis europaea relies on the lovely, and strictly wetland, plant Yellow Loosestrife (Lysimachia vulgaris). The latter can be found in large stands near some waterways and it is always worth looking for the bee in such places.

Females, who have white scopae (pollen brushes) not only collect pollen pretty well exclusively from Yellow Loosestrife; they also rely on oil the plant contains to provide waterproofing for the nest, which is in soil in damp areas. The oil is turned into a wax-like substance. Male Macropis europaea have a yellow face.

The yellow-faced bee Hylaeus pectoralis is commonest in West Sussex, Hampshire and Dorset and needs stands of Common Reed (Phragmites australis). Nests are constructed inside vacated cigar-shaped galls of the Chloropid fly Lipara lucens, with up to eight cells per nest.

A number of hoverflies have an association with damp habitats. Anasimya contracta (8mm) is striking in looks with aquatic larvae. In contrast, Eristalinus sepulchralis (12mm) is relatively drab. However, it is distinguished by its spotted eyes. These are unique among the family and give it much more the look of a horsefly. They are pretty active and their larvae need enrichment, as in rotting vegetation or even manure. Ripponensia splendens (9mm), the only member of its genus in Britain, is bright as a button in all areas of the body. They peak in July and are fond of flowers in general and umbellifers in particular. Neoascia interrupta (7mm) was added to the British list in 1981 and has subsequently been recorded quite widely in south-east England, suggesting that its nationally scarce status may not be wholly accurate.

A number of soldierflies and their allies have a close link with wetlands and one of the banner species is the Clubbed General (Stratiomys chamaeleon, 12mm), with the female pictured at the top of this page and the male shown via the link just given. This is an Endangered species found in only one area in England, Oxfordshire. The larvae develop in wet mud, and shallow water with a high calcium content in sheltered pools that warm up quickly. Adults are mostly seen in July and August on umbellifers.

From the same genus but doing rather better is the Banded General (Stratiomys potamida, 12mm), which has increased its range over the last 30 years. The brilliant yellow markings, size and shape of both these Stratiomys species set them apart from most in the family. Certainly the Black Colonel (Odontomytia tigrina, 8mm) is one that looks monochrome by comparison.

Sexual dimorphism is clear with the Black Snipefly (Chrysopilis cristatus), a common species around well-vegetated water bodies. The male is dark and relatively skinny but the female is paler and quite dumpy.The larvae live in wet mud and are claimed to have toxic properties.

Snail-killing flies are often found near water and one of the most striking is Sepedon sphegea (8mm), which has orange-red femora and tibiae. This is a widespread species. It is not the adults that kill snails but the larvae.

Common Gnats (Culex pipiens, 5mm) have egg rafts which produce vast numbers of adults but they are not in the habit of biting humans, aiming mainly at birds, which presumably get their own back by catching and eating a lot of gnats.

Two ladybirds, one pretty common and one certainly not, have a close association with wetland. The Water Ladybird (Anisosticta 19-punctata, 4mm) is best looked for on reeds, where it hunts aphids, and is present year round. The orange colouring of the spring changes to beige by late summer. The species winters in sheltered spots in the vegetation it inhabits. The Five-spot-Ladybird (Coccinella 5-punctata, 4mm) was never common in the area covered by this website. Now seemingly it is extinct, being limited to parts of Wales and Scotland. It is associated with unstable shingle on rivers though it occupies other habitats in mainland Europe.

Most bush-crickets are suited by dry conditions but an exception is the Short-winged Conehead (Conocephalus dorsalis, 16mm), which used to be found exclusively near the coast but has been spreading inland and is now fairly common in wet or damp areas in the south of England. Warmer summers may be helping this development.

Swallowtails (Papilio machaon, wingspan 85mm) are not only magnificent but also one of a mere handful of butterlies specialising in wetlands, and as a result of their requirements - the only foodplant for larvae is the rare Milk Parsley (Peucedanum palustre) - the species is restricted to parts of Norfolk.

In those localities, such as Catfield Fen National Nature Reserve and Hickling Broad, it is doing well. However, long-term survival depends on so many variables, including regularly cutting reedbeds to enable the foodplant to thrive (it grows only in very wet marshes), that one cannot be entirely confident about the butterfly's future. Swallowtails are on the wing in June.

Also seen in June is the Elephant Hawk-moth (Deilephila elpenor, wingspan 70mm), which is the commonest of the group and found in a wide variety of habitats. Wetlands are one of these since two of the moth's foodplants are Bogbean and Great Willowherb.

Elephant Hawk-moths gain their name not from the appearance of the adult, which is one of the prettiest of the hawk-moths, but from the remarkable way the caterpillar can change its shape when threatened. The head retracts and the front of body, dominated by two false eyes, swells up.

Images © Jeremy Early. All rights reserved.

In 2013 I published My Side of the Fence - the Natural History of a Surrey Garden. Details may be found, and orders placed, via this hyperlink My Side of the Fence. In November 2015 Surrey Wildlife Trust published the atlas Soldierflies, their allies and Conopidae of Surrey, jointly written by David Baldock and me. Details are on this web page: Atlas.