Freshwater Life - A field guide to the plants and animals of southern Africa

11	Text by Fabian Haas

Earwigs, crickets and grasshoppers

Earwigs

Order Dermaptera

Medium-sized insects (10–15mm in length) with typical forceps-like structures at posterior end. Show maternal care, the mother cleaning and defending the eggs (10–50 in a batch) and attending first instar nymphs. Intricately folded hindwings concealed under short and leathery forewings. Depending on species, forceps are used to unfold the wings in a fairly slow process, thus flight is never used in escape. Forceps are also used in courtship behaviour, defence and catching prey. Earwigs are not true water insects, but some prefer a moist (micro-) habitat. Most are omnivorous. About 50 species occur in southern Africa, but only a few are associated with water.

1 Tawny (Giant) earwig

Labidura riparia

A large, winged earwig with long antennae and forceps (larger and more curved in male, 1). Light brown to yellow in colour, often with darker stripes on forewings. Digs small tunnels and chambers under stones and debris where it hides, broods and cleans batches of large white eggs (1a). Size: Up to 30mm. Biology: Requires sand, and is thus often found along river banks and on beaches, where it actively hunts for other small arthropods. Raises forceps over head when threatened (1b).

Crickets and grasshoppers

Order Orthoptera

Medium-sized to large insects with strong chewing mouthparts; wings may be reduced or absent. Hindlegs modified for jumping. Many produce intense sounds in a variety of ways: crickets use specially modified forewings, while grasshoppers use forewings and hindlegs for sound production. Locusts can be major crop pests; some, like the Migratory locust, are significant pests on a global scale. Eggs deposited with an often sword-like ovipositor into soil, or into living plant tissue, including that of water plants. Some herbivorous species feed only on water plants.

2 Pygmy mole crickets

Family Tridactylidae

Shiny black or sand-coloured. Similar habits and life history to African mole cricket (see 4, below), but not closely related to it and forelegs not strongly modified. Hindlegs enormously enlarged, with characteristic large tibial spur and swimming plates. Forewings reduced, but hindwings present and capable of flight. Size: <20mm in length. Biology: Strong swimmers on and below surface. Can jump from water surface; on ground exhibit formidable jumping abilities. Dig and occupy short tunnels in moist sandy places, usually near streams or artificial water bodies. Emerge from burrows to feed on plant detritus and algae. Three genera in region: Tridactylus has one species in South Africa, Afrotridactylus has two and Xya (2) has seven.

3 Groundhoppers (Grouse locusts)

Family Tetrigidae (Tettigidae)

Superficially small grasshoppers, but with a massive dorsal extension of the thorax, which extends backwards over the abdomen and often beyond its tip. Forewings small and scale-like; hindwings well developed. Size: 7–20mm in length. Some species squat and flightless. Biology: While not strictly dependent on water, commonly found on moist bare ground around margins of lakes and dams. Many species swim and dive well and sometimes rest by clinging to water plants. Feed principally on plants and algae. Eggs laid in batches in the soil, without bonding glue.

4 African mole cricket

Gryllotalpa africana

A strongly built brown cricket with large prothorax and massively developed forelegs, highly modified for digging in soil, much like the forelimbs of moles. Well-developed short forewings and large fan-like hindwings, the tips of which stick out like spikes when folded. Size: 25–33mm in length. Biology: Found in humid to wet soils close to the banks of rivers and pools, but also on irrigated lands. Good swimmers and flyers, they live in soil and dig extensive tunnels and galleries up to 100cm long (4a), gnawing on roots, rhizomes and tubers, but also taking earthworms and insects. May occur in masses, when they can become general plant-eating pests. G. africana may actually comprise several similar but distinct species.

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