Ibacus peronii

Ibacus peronii, the Balmain bug or butterfly fan lobster, is a species of slipper lobster. It lives in shallow waters around Australia and is the subject of small-scale fishery. It is a flattened, reddish brown animal, up to 23 cm (9 in) long and 14 cm (6 in) wide, with flattened antennae and no claws.

Description

In common with other slipper lobsters, Ibacus peronii has a broad, flattened body and a large carapace. The carapace is reddish brown, and reaches lengths of 2–8 centimetres (0.8–3.1 in), with the whole animal able to reach a length of 23 cm (9 in), and a width of 10–14 cm (3.9–5.5 in). The antennae are also short and broad, and the flattened form of the whole animal allows it to partly bury itself in soft substrates. There are no claws on the five pairs of legs. Captured animals typically weigh around 120 grams (4.2 oz), but the weight can range from 80 to 200 g (2.8 to 7.1 oz).

The species is sometimes confused with the Moreton Bay bug, Thenus orientalis, but they can be distinguished by the placement of the eyes: the eyes of I. peronii are near the midline, while those of T. orientalis are at the margin of the carapace.