Techniques for assessing infestation trends of Latoia viridissima are presented in this report. A plot of the head capsule widths of larvae indicated six larval instars with instars one and two being more abundant. It also illustrated the composition of larval instars in the population and hence would serve as a standard against which future samples of the species could be compared. Larval survivorship data indicated heavy mortality (>60%) during instars one and two. Major mortality factors were an aggregate of natural enemies, particularly predators (causing 40–50% of the death during the age interval), parasitoids and pathogens responsible for 60–80% mortality throughout the entire larval life. The residual cocoon populations were further reduced by about 20–30% by parasitoids (Brachymeria sp., Chrysis spina, Cocygodes coccyx, Palexorista sp and Systropus pelopoeus) and a pathogenic fungus. Data from cocoon samples showed that the sexes of the moth could be separated on the basis of cocoon size. Cocoon weights were therefore, a better criterion than cocoon diameter values for separating the sexes; since overlap between the sexes was less than 5 % for cocoon weight as against 20% In the case of cocoon diameters. The separation point tended to lie between cocoons weighing 350–399 mg. Fecundity of the females was highly correlated with female weights (r = 0.901) and wing length (r = 0.89), The calculated fecundity of 143 eggs/female (using wing length) was not statistically different (P ≤ 0.05) from the observed value of 149 eggs/female. The significance of the findings as regards forecast of outbreaks and assessment of outbreak situations are discussed.

Field studies revealed the nettle caterpillar, Latoia ( = Parasa) viridissima, to be multivoltine with four discrete generations a year. The maximum egg (1800/100 fronds) and larval (1500/100 fronds) densities were attained in April/May 1980. The pupal population was generally low; the highest recorded density of 54/100 fronds was attained in March 1980 during the first generation.

Samples of larvae and pupae from the field were attacked by parasitoids in the families Bombyliidae, Braconidae, Chalcididae, Chrysididae, Eulophidae, Ichneumonidae and Tachinidae. These contributed to mortalities ranging from 6 to 30%, but their combined action with microorganisms (bacteria and fungi) accounted for 28–65% mortality of the insect.