Balmain bug

Ibacus peronii

Crustaceans
IUCN: Least concern

Usual depth52–199 m
Water temperature15–28 °C
Best monthsFebruary, July, and November
How commonOccasional

Photo credit: no rights reserved · CC0 1.0 · iNaturalist

About this species

Ibacus peronii, commonly known as 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.

Text from the Wikipedia article “Ibacus peronii”, licensed CC BY-SA 4.0. Read the article

Where and when

Where it has been recorded

Worldwide

Loading the map

Best months

Worldwide (open data)

January: 11 records
February: 34 records
March: 17 records
April: 10 records
May: 16 records
June: 21 records
July: 47 records
August: 22 records
September: 18 records
October: 27 records
November: 29 records
December: 13 records

Depth and water temperature

Depth

Mostly recorded at 52–199 m · Deepest record: 241.4 m

40–50 m: 1 records
50–60 m: 5 records
60–70 m: 3 records
70–80 m: 0 records
80–90 m: 0 records
90–100 m: 0 records
100–110 m: 2 records
110–120 m: 1 records
120–130 m: 0 records
130–140 m: 1 records
140–150 m: 0 records
150+ m: 5 records

Water temperature

Recorded in surface water of 15–28 °C

14–16 °C: 50 records
16–18 °C: 11 records
18–20 °C: 11 records
20–22 °C: 46 records
22–24 °C: 9 records
24–26 °C: 4 records
26–28 °C: 2 records
28–30 °C: 2 records

Names and classification

English: Balmain bug, Butterfly fan lobster, Butterfly lobster, Flapjack, Péron's Ibacus crab, Prawn-killer, balmain bug, butterfly fan lobster, butterfly lobster, flapjack, prawn-killer, sand crayfish, sand lobster, southern shovel-nosed lobster, squagga

Other scientific names: Phyllosoma Duperreyi, Scyllarus incisus

Similar species

Deep water bug
Ibacus alticrenatus
Japanese fan lobster
Ibacus ciliatus
Digging lobster
Ibacus novemdentatus
Serrate fan lobster
Ibacus brevipes
Glabrous fan lobster
Ibacus brucei
Ibacus chacei

Sources and credits

Names and taxonomy: WoRMS (CC BY 4.0) and the GBIF Backbone (CC BY 4.0). Photos: iNaturalist observers, each under the licence shown (CC0, CC BY or CC BY-SA).

Depth, temperature, months and maps: records from OBIS and GBIF under CC0 or CC BY.
Descriptions: Wikipedia, licensed CC BY-SA, each linked to its article.
Conservation status as published by GBIF (IUCN Red List).
238 open-data records from 1890 to 2007.
Species data updated November 3, 2026.

Log what you see on your next dive

The free DiveHive diver app keeps your logbook with every sighting and shows what lives at the site you dive next.

Join the waitlist