L'aggregazione in Ceratomegilla undecimnotata Schneider (Coleoptera Coccinellidae): indagini preliminari sulla caratterizzazione chimica degli idrocarburi cuticolari e dei composti volatili presenti

Some species of ladybirds aggregate during summery and winter period. This phenomenon has been object of numerous studies in order both to understand its ethological meaning, and -potentially- to improve the employment of these predators in organic farming technique. Induction to summer migration seems correlated to photoperiod, temperature and hormonal pattern while onentation towards the tops of mountains appears related to visual stimuli. In this work, authors report some results in the attempt to identify contact and volatile compounds involved in aggregation of C. undecimnotata. Analyses were made in GC-MS both of heptanes extracts and volatiles collected using SPME technique. These expenments allowed us to identify hydrocarbon profiles of aggregate individuals. In particular approximately 28 compounds have been described, the most abundant of which are saturated and monounsaturated hydrocarbons with long chains from 23 to 33 carbons. No significant differences in hydrocarbons composihon were found between males and females and also between an Itallan and a French population. Analyses of head spaces in SPME have shown low concentrations of volatile compounds, among which a characteristic peak of palmitic aldehyde was determinate. These data, although preliminary, are the first GC-MS investigation on aggregate pheromones of C. undecimnotata. They will be used to devise behavioural bioassays and to establish the function of identified compounds.