Broad types of caterpillars

Itchy Caterpillars

Caterpillars that have non-venomous hairs that cause mechanical irritation, hypersensitivity type reactions or foreign body reactions.
  • Often a problematic diagnosis: patients or a group of may present with an unknown rash, usually a papulourticarial rash. There is rarely a history of contact with a caterpillar. The rash can result from contact with the itchy caterpillars or from airborne caterpillar hairs. The season, geographical location or collection of cases (outbreak) is usually how the diagnosis is made.
  • History: important to establish the source of the caterpillars or caterpillar hairs.
  • Examination: papulourticarial rash that may come and go depending on exposure to the caterpillars. Sticky tape testing can be done where sticky tape is applied to the rash and then examined under the microscope for caterpillar like hairs.
  • Treatment: removal of the source of caterpillars and symptomatic relief.

Mistletoe Brown-tailed Moth (Euproctis edwardsi)
This is probably the commonest cause of caterpillar dermatitis in Australia and has been responsible for many outbreaks in Eastern Australia.
Balit C, Ptolemy H, Geary MJ, Russell RC, Isbister GK. A caterpillar dermatitis outbreak following contact with the hairs of the Mistletoe Browntail moth (//Euproctis edwardsi//) Med J Aust 2001; 175:641-3

Stinging Caterpillars

Caterpillars that have hollow spiders that contain venom that is injected when pressed against skin.
Stings usually cause local raised wheal type reactions that last a few hours to a day. Treatment is symptomatic for the majority of cases.
  • Limacodidae
    • Doratifera spp. : common in most parts of Australia, “spit-fires”
    • Thosea penthima
  • Nolidae Uraba lugens
  • Megalopygidae
    • Megalopyge opercularis “puss’ caterpillar U.S.
  • Saturnidae
    • Lonomia spp. in South America – severe systemic effects
Figure: Sting from a caterpillar in NSW Australia commonly referred to as a spitfire (Picture by Michael Downes)

Lonomia spp. (South America)

  • Severe systemic envenoming
  • Previously: acute renal failure occurred in 18% of cases and was fatalities occurred.
  • Antivenom is now available.