Background: Investigating movement ecology of organisms has economic, societal, and conservation benefits. Larval movement of insects for example, plays many significant ecological roles, and with the expansion of the human population and development, encounters and conflicts with insects have increased. Urticating caterpillars are a health concern to people and animals, especially when they disperse in a gregarious and synchronised manner in areas frequented by humans. Ochrogaster lunifer and Thaumetopoea pityocampa from the southern and northern hemispheres respectively, are two geographically-isolated species of moth with similar gregarious urticating caterpillars that can outbreak causing defoliation and medical issues. Methods: Each year from March to May, O. lunifer and T. pityocampa caterpillars leave their nesting sites and form head-to-tail processions on the ground in search of pupation sites. This pre-pupation procession behaviour and its associated risk of human contact with O. lunifer and T. pityocampa caterpillars were studied and compared in Australia and Italy, respectively. The distance, duration, orientation and response to visible light of the pre-pupation processions were studied in both species to determine general patterns. Results: In the morning, O. lunifer and T. pityocampa processions travelled on average 40 and 16 m per day from the nest in 153 and 223 min respectively, in search for potential pupation sites. Ochrogaster lunifer pre-pupation processions travelled generally to the north or south when leaving the nest, as was their final orientation to the bivouac/pupation site. Whereas T. pityocampa processions had no preference in orientation. Ochrogaster lunifer and T. pityocampa pre-pupation processions travelled towards the darker and the lighter areas of the environment, respectively. During our observations, 27% of O. lunifer and 44% of T. pityocampa processions had contact with humans driving, cycling or walking. Conclusions: The amount of human contact is surprising and alarming, because of the serious health implications they cause to humans and animals. The processionary dispersal on the ground risks further spread of urticating hairs that can be easily detached, and particular during inadvertent contact. Our limited sample size of T. pityocampa processions may benefit from more observations to make conclusive remarks on their pre-pupation behaviour. Understanding the movement behaviour of O. lunifer and T. pityocampa pre-pupation processions around populated areas is crucial for predicting exposure risk and application of management strategies.

Establishing in the right location is particularly important for larval insects. Lepidopteran females are generally selective when choosing oviposition sites to ensure the best survival for their offspring. Unlike most social and shelterbuilding Lepidoptera, egg batches of the pine processionary moth, Thaumetopoea pityocampa Denis & Schiffermüller (1775) (Lepidoptera: Notodontidae), are oviposited randomly on the host tree. Thaumetopoea pityocampa is gregarious throughout all larval instars and live in silken tents, spun repeatedly and maintained by the colony during larval development. In this study, a single T. pityocampa egg batch was transplanted on Pinus nigra trees free from natural egg batches in one of four compass orientations: north, east, south or west. The orientation of transplanted egg batches had no significant effect on the final survival of the larvae. Thaumetopoea pityocampa larvae were behavioural thermoregulators from first to final instar and tended to position their tent in a southerly orientation for maximum sun exposure. Thermoregulation was the utmost priority for T. pityocampa larvae as they feed through the winter. Feeding behaviour and number of tents built by early instars changed as larvae became older, and this could be explained by natural enemy avoidance and/or evasion of plant defence. The results can help predict larval movement and assist in pest management strategies for T. pityocampa at a microhabitat level. This study is the first to investigate detailed movement behaviour of all T. pityocampa larval instars on a host tree, describing the transition of larvae starting as patch-restricted foragers to central place foragers.

Each life stage of an insect faces the challenge of various mortality factors. Through experimental and observational studies, we use those mortality agents to our advantage to control outbreaks of pest insects. The processionary caterpillar Ochrogaster lunifer Herrich‐Schäffer, 1855, is a widespread native moth in Australia that defoliates host trees and causes medical problems in humans and animals. Anastatus fuligispina (Girault 1939) is an egg parasitoid described from eggs of O. lunifer in eastern Australia nearly 80 years ago for which few life history traits are known. This is the first study to investigate the life history of A. fuligispina, factors associated with parasitism levels in O. lunifer egg masses and its impacts on egg mortality. We found that parasitism level was related to the total number of eggs in an O. lunifer egg mass, with higher parasitism occurring in masses with fewer eggs. The inaccessible physical structure of the O. lunifer egg mass by layering and encasing eggs with other eggs and the searching efficiency of the parasitoid are possible key factors. Other variables such as exposure time in the field, host tree species and number of undeveloped eggs in the egg mass did not affect the level of parasitism. Further investigations on the life history of A. fuligispina may open possibilities for its application in controlling O. lunifer populations.