Segregation and behaviuor of the parasitoid of longhorn beetles Sclerodermus brevicornis (Hymenoptera Bethylidae) in laboratory choice tests

Maternal care is an important and characteristic behavior in quasi-social parasitoids. The coexistence of numerous individuals on the same host helps to protect the offsprings from parasitism and conspecific intruders. Some researches has evidenced that also kinship relation can affect behavior and performances. In this study, we investigated some behavioral traits of Sclerodermus brevicornis (Kieffer) (Hymenoptera: Bethylidae), a quasi-social wasp found in association with Psacothea hilaris hilaris (Pascoe) (Coleoptera: Cerambycidae). We studied the ability of this species to aggregate/segregate as well as the reproductive ability when two hosts of the same dimension and species are available (P. h. hilaris larvae of 0.036±0.02g). Five choice tests, with 14 replicates each, were set up under controlled conditions with a different number of adult females (2-4) and a different degree of kinship (none, two siblings, all siblings) in a completely randomized design. Experiments were observed three times per day until offsprings emergence and data about segregation, movement, oviposition and offspring development were acquired. The aggregation between sibling and non-sibling differed significantly (F4,123=3.955, p=0.007) and in detail, in the tested conditions, emerged the preference of being alone or in the company of unrelated. This was also confirmed by the statistically significant differences between oviposition in sibling and non-sibling groups. All groups generally preferred to oviposit on both larvae in the test. Unexpectedly, females changed the host after paralysis and acceptance, moving from one host to the other and influencing, in some cases, the success.