Does Hermetia illucens recognize sibling mates to avoid inbreeding depression?

Management of genetic diversity in Hermetia illucens L. (Diptera: Stratiomyidae) commercial colonies is a key problem. Inbreeding depression can affect the maintenance and sustainability of insect farming, in particular small-scale mass-rearing, by reducing population fitness or causing colony collapse. In animals, kin recognition could play a role avoiding inbreeding and mating with sibling. To determine inbreeding impact in a H. illucens laboratory strain, the courtship and mating behaviour occurring between unrelated or full-sibling mates were compared in controlled crosses. Furthermore, selected lifetime parameters, including egg laying and fertility, developmental time, total fecundity, and sex ratio, were compared. Inbreeding depression can be observed by second generation of full-sibling mating, with a severe reduction of produced progeny (emerged adults per female, No-Sib: 234.9 ± 38.0 vs. Sib2: 64.3 ± 16.7). No differences attributable to kin recognition were noted in the pre-copula and post-copula behavioural sequences. However, copulation was prolonged in inbred mates (No-Sib: 35.5 ± 2.8 min vs. Sib2: 52.2 ± 6.4 min), probably due to the physiological characteristics of the mates. Nevertheless, a valuable restoring impact of backcross on several life-time parameters was also observed, mitigating the impact of inbreeding depression. This research provides valuable information about inbreeding and mate selection to avoid population depression in H. illucens. Further studies are needed to investigate the occurrence of other selection mechanisms in this species, as well as the possible impact of outbreeding on population fitness.