Timing of failed parasitoid development in Halyomorpha halys eggs

Invasive species can destabilize ecological communities by becoming novel hosts, prey, predators or competitors for native species. They can have lasting effects on population dynamics when they reduce the fitness of native individuals. The establishment and spread of invasive Halyomorpha halys, in Europe and North America, have presented native natural enemies in the introduced areas with such a challenge. The native parasitoids readily parasitize eggs of H. halys, but their progeny rarely develops in fresh eggs of this host. The barriers to successful development of native parasitoids in H. halys eggs remain unidentified, and the affected developmental processes therein remain unclear. To determine the timing of failed development of native parasitoids in fresh H. halys eggs, we examined the temporal development of the Trissolcus euschisti parasitoid within suitable (Podisus maculiventis) and unsuitable (Halyomorpha halys) host eggs using a DNA barcode-based approach, and in situ 3D visualization by X-ray micro-computed tomography (micro-CT). Trissolcus euschisi parasitoid development in fresh H. halys eggs fails soon after parasitization either during the egg stage or during early-stage larval development, as limited or no larval development was observed 24 h after initial parasitization. In light of these findings, we propose a time window for further investigation of several potential mechanisms that might result in failed parasitoid development in H. halys.