Insects of Chesworth Farm wetland

The Six-spot Burnet is a regular day-flying moth and seen on the wing throughout the farm from June right through to August. It loves the flowers of open fields such as Common Knapweed and all species of thistles. Its larvae feed on many of the plants found in these and other fields throughout the farm and these include both the Common and Greater Birds-foot Trefoil.

Two of our regular hoverfly visitors to the waterside plants in the Riverside fields are the sun flies. These insects form a small group of hoverflies that all show the boldly striped thorax, which provide their alternative name of “the Footballers”. We have two species that regularly visit the flowers around the water meadows Helophilus pendula (meaning hanging-marsh-lover) and H. hybridus. You may hear them “buzzing” as they sit on the flower heads. Their larvae, the rat-tailed maggots, live in ponds and wet areas around manure heaps – where there is plenty of decaying vegetation.

Rat-tailed maggots are the larval form of a small number of hoverfly species (including the two species of sun fly mentioned here). These are the largest of the hoverfly larvae and as their name suggests have an extended “tail”. This tail holds the breathing tube that it extends to the water surface enabling these grubs to breathe. A delicate array of small hairs, setae, around the end of the tail prevents water from entering the breathing tube. The rat-tailed maggots generally filter-feed on small underwater organisms found in rotting and decaying vegetation. Here the deep pits left by cattle’s hoof-prints at the water’s edge can provide the ideal conditions for these maggots to live.

Despite the pressures faced by many of our bumblebees the Common Carder Bee (Bombus pascuorum) seems to be expanding its range, probably because of its wide taste in habitats. They can be seen on most of the fields around the farm – wherever there are flowers, really. The new queens emerge from hibernation early in the year (March) and start searching for nest sites, which are made underground. To cover their nest they gather moss by scrabbling among the grass sward – an activity that gives rise to their common name.

A dragon or a damsel?

ruddy darter

Common Darter

One of the easiest ways to tell the difference between dragonflies and damselflies (often known by the name of their scientific order, ‘Odonata’) is to look at their wings when they are still. The dragonfly has wings that remain at right angles to the body while damselflies lay parallel over their body and tail.

Of all the dragonflies that visit this area, the Common Darter (Sympetrum striolatum) is probably the one you are most likely to see – and one to which you will get closest! The mature males are almost completely red in colour while the females and young are orange/yellow to tan. The other darter that can regularly be seen around the boardwalk is the Ruddy Darter (Sympetrum sanguineum). Although very similar to the Common, the Ruddy Darter has all black legs and a slightly “clubbed” abdomen. Both species can be seen from June through to November in good years but are most abundant in July and August. The Common Darter is known for its ability to establish itself in new ponds and is probably one of the commonest insects in this group.

A large, easily-identified dragonfly, the Four-spot Chaser (Libellula quadrimaculata), is often seen resting on rushes and grass stems. The wings clearly show the dark spots from which it gets its name (although you can argue that there are eight altogether). There are two further dark patches at the base of each hind wing that are much bigger on the males. As its name also implies, it chases its prey and is seen most often flying purposefully over the open water, hunting.

The Azure Damselfly (Coenagrion puella) is on the wing from early April and can be seen all the way through to September in good years. At Chesworth the best months are June and July. The adult males are the beautiful blue colour while the females are a rather drab green.

Other dragonflies and damselflies you may see over our wetland but not shown on the interpretation board, include:

Banded Demoiselle (Calopteryx splendens), Beautiful Demoiselle (Caloperyx virgo), Emperor Dragonfly (Anax imperator) and Southern Hawker (Aeshna cyanea). Both of the demoiselles are usually seen in the earlier part of the summer season – from mid May through to early September. The dragonflies however, generally emerge a bit later from mid June – but may still be seen on the wing in October.

LINKS

British Dragonfly Society – Sussex Group

Sussex Moth Group

Bumblebee Conservation Trust

Illustration by Helen Joubert Design

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