Itchy caterpillars

Family

Lymantriidae

Euproctis lutea (formerly Porthesia lutea) Fabricius. Identified by R. Southcott, South Australia.

Food plants

Collected by P. Whelan on the Barringtonia acutangula (L.) Gaertner (Freshwater Mangrove), Darwin 7 April 1982, and on the Planchonia careya (F. Muell.) R. Knuth (Cocky Apple), Jabiru, July 1982 and Katherine, May 1980.

Appearance

The early larval instars (caterpillar larval stages) are a pale cream with sparse medium length hairs, and an almost hairless appearance. The later instars are a pale light brown with a darker patch of four tufts just behind the head region and two darker tufts at the rear end. The moth is pale yellow with a fine pattern of lighter yellow lines.

Biology

The primary food plant appears to be the Freshwater Mangrove, although it is seasonally common on the Cocky Apple. It is found generally across the Top End of the Northern Territory (NT). 

The eggs are laid as a pale scale covered mass on the leaf surface of the food plant. The larvae on hatching, feed together on the same leaf for the first instars and weave a thin silken shelter across the surface of the leaf beneath which they shelter. The early instars leave a characteristic skeletonised portion on the leaf. If a larvae is dislodged from the leaf they are suspended by a silken thread and soon climb back to the leaf. 

During the later instars, the larvae are found sheltering on the shaded side of the base of their food tree in a silken shelter, together with shed skins. The adult moths are strongly attracted to light and can rest and lay egg-masses on surfaces near the attracting light. They will alight on pale surfaces such as sheets and clothing on clothes lines at night.

Medical effects

I brushed a mature larvae on the inside forearm and very soon produced white 3mm x 3mm urticarial lumps surrounded by a large (5cm x 5cm) reddened area. The arm was extremely itchy from one minute to two hours afterwards. Contact with the scales covering the egg mass can produce the urticaria reactions as well.

Contact can be made with the early instars by walking beneath or even close to the food tree. Touching the trunk of the tree when later instars are present is sufficient to come into contact with the poisonous hairs. Touching the affected area of the skin and then touching an unaffected area often leads to a spread of the problem. The silken shelters and shed skins can cause reactions months after the larvae are no longer present.

Symptoms can also be experienced from touching the mature moths. In April 1982 while two kilometres offshore from Port Keats, NT I handled the yellow female moth of this species attracted at night to light and inadvertently touched the region of my left eye. The eye region became itchy within a few minutes and soon became very itchy and uncomfortable and started to swell. After one hour the eye swelling completely obscured the vision in the eye, and the eye area was still swollen, although not itchy, 12 hours later.

On another occasion I awoke with itchiness on a bunk well out to sea, and observed an extensive urticarial rash on my trunk. An examination of the sheets revealed a moth of this species, and removal of the moth was sufficient to avoid further problems.

Young children have been observed with appreciable swelling around the eyes , ears and throat areas, and some with appreciable reactions have required medical attention.

P. Mackey (pers. com) reports itches for days after touching the moths.

Remedy

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 the application of a residual 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 yellow 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 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.

Reference

Southcott, R.V., 1978, ‘Lepidopterism in the Australian region’, Records of the Adelaide Children’s Hospital, vol. 2, pp. 87–173.

Southcott R.V. Moths and butterflies in Covacevich J, Davie P, and Pearn J, (editors)1987, ‘Toxic plants and animals, A guide for Australia’ Queensland Museum.