Alarodia nana (Möschler) (Lepidoptera, Limacodidae) is a major pest of Citrus in Jamaica. An outbreak of the larvae, the ‘ slug caterpillar ’, may result in severe defoliation. All stages are found on the foliage and are present throughtout the year; the adults are inactive by day and appear to be weak fliers.

Earlier attempts to breed the insect in the laboratory had been unsuccessful, and, whereas attempts at control had indicated that malathion was effective against the larvae, reingestation had invariably taken place, well-grown larvae being found five weeks after treatment.

In the present work, done in 1963–4, adults that emerged from field-collected cocoons held in wire-mesh cages over Citrus plants in the laboratory mated on the night of emergence and the females oviposited readily on the following night. A technique for rearing individual larvae and for measuring their head capsules is described. In the laboratory at a mean midday temperature of about 27°C., the incubation period of the eggs was 6–8 days, and the durations of the larval and pupal phases 25–42 and 14–19 days, respectively.

Results of a search for secondary host-plants from which reinfestation might take place were negative. Observations of emergence in the laboratory of adults from cocoons collected just before and just after the application to an orchard of a low-volume malathion spray derived from a 57 per cent. emulsifiable concentrate by dilution at the rate of 1: 80 in water showed that many pupae had survived the application, and suggested that reinfestation might arise from moths emerging from such pupae.

A field trial comprising two application of the low-volume spray of malathion was carried out; the second application, designed to destroy larvae derived from pupae that had survived the first application, was made after an interval of 312; weeks and was completely successcful.