Itchy caterpillars

Cocky apple stinging caterpillar



Thosea penthima Turner (Identified E.D. Edwards 24/5/00)

Food plants

Collected from Planchonia careya (F. Muell.) R. Knuth, (the "Cocky Apple or Billy Goat Plum") in Darwin 12/3/82 and Terminalia ferdinandiana the "Kakadu Plum" in Darwin, March 1982 by P. Whelan and W. Kelton.


A pale yellow and light green larvae with an oval flattened appearance with numerous protuberances along each side and two rows of protuberances dorsally. The moth is light brown and of medium size with a thin dark line transversely across the forewing.


The main food plants are Terminalia ferdinandiana and Planchonia careya. Infested trees or shrubs usually have the appearance of eaten leaves but there may be only a few larvae on each tree. 

Pupation occurs in a relatively hard parchment-like ovoid cocoon between or on leaves, with a flattened portion at the site of attachment to the leaf. Exposure is often from walking with bare legs through regrowth of annually burnt or cleared Eucalyptus woodland, in the early to mid wet season when small shrubs of Planchonia careya or Terminalia ferdinandiana are usually present.

Medical effects

Contact with the caterpillar to the rear of my thigh resulted in a sharp painful burning sensation which intensified after 15 minutes with a muscle ache. 

The ache was reduced after 25 minutes with a continuous burning sensation. After one hour, there was a mild burning sensation which had subsided by one and a half hours. I have experienced a number of very sharp and painful stings from these species.


Avoid food trees in urban or bush settings, particularly if there is evidence of fresh skeletonising or partly eaten leaves.

Remove trees in urban sites or destroy larvae at resting stage at the base of the food trees by residual application of insecticide to the trunk or leaves of the tree and by wrapping loose bagging impregnated with insecticide at the base of the tree. Burn the area around the base of tree during the day when the caterpillars are resting.

Do not have outside fluorescent or incandescent white lights on after sundown in problem areas or when moths are active.

Do not touch the light brown moths.

Do not sleep or sit under lights when the moths are attracted to the lights.

Wash affected clothes or skin well with soap and water.

Apply ice packs or soothing lotions such as Stingose, Calamine Lotion or papaya creme. Antihistamine medications may be required for severe or generalised reactions. Medical advice should be sought for severe reactions.


Isbister GK and Whelan PI. 2000. ‘Envenomation by the billygoat plum stinging caterpillar (Thosea penthima)’. Medical Journal of Australia. 173:654-655.

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Last updated: 29 August 2016

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