New paper on the behaviour of processionary caterpillars
Recently, a new paper on the Movement behaviour of two social urticating caterpillars in opposite hemispheres has been published in the Movement ecology journal. This is a step towards developing surveillance and delimitation tools for emerging and invasive pests and pathogens on trees and forest - one of the key goals of the HOMED project. To develop such tools, researchers first need to understand the behaviour of these organisms. Behaviour of pre-pupation processions of Ochrogaster lunifer and Thaumetopoea pityocampa have been described before, however, all studies contained no quantitative data and analyses of the processions.
The current study on the movement behaviour of the two species of urticating processionary caterpillars determines where they disperse in the environment to pupate. The paper is a foundation for investigating the cues these urticating Lepidoptera use from the environment to navigate, with a focus on vision. The next step will be to mitigate harmful impacts on humans and animals.
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.
Thaumetopoea pityocampa and Ochrogaster lunifer are urticating species of processionary moths that are medically important in Europe and Australia, respectively. Every year from March to May in Australia and Italy, both species of mature larvae leave the nest in a procession from the host tree to search for a suitable pupation site underground. During this period, it is the highest risk for humans and animals to encounter processions and can result in serious health problems. The aims of the research were to determine the distance, duration, orientation and response to visible light of the processions traveling from the nest/first sighting to the potential pupation site. Pre-pupation procession behaviour of the two species was explored and compared in an Italian pine forest and semi-urban university campus in Australia, respectively. Thaumetopoea pityocampa processions travelled to lighter areas of the environment in no preferred orientation, whereas, Ochrogaster lunifer processions travelled to the darker areas of the environment generally towards north and south. A valuable outcome of this research is that knowledge of dispersal movements in these important pest species can facilitate building models to predict exposure risk and application of pest management strategies.