Functional morphology of the sting in two digger wasps (Hymenoptera: Crabronidae) with different types of prey transport.

Digger wasps of the family Crabronidae (Insecta: Hymenoptera) are generally known to use their sting to paralyze or kill a prey. However, only a few species of digger wasps transport their prey to the nest impaled on the sting. How sting morphology correlates with this peculiar type of prey carriage is still unclear. We examined the sting morphology of two phylogenetically closely-related species of digger wasps of similar size, which hunt for similar preys but use different types of prey transportation. Data from light microscopy (LM), scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) were analyzed to find possible correlations between shape, material composition, and function of the stings. The similarity of the material composition in the stings of the two species suggests that the material of stings does not play a dominant role in their functional differences. On the contrary, differences in the curvature and surface sculpture of sting elements likely result in different stress distributions under mechanical loading.

Stylus of the odonate endophytic ovipositor: a mechanosensory organ controlling egg positioning.

Using light and scanning electron microscopy, a sensory field consisting of 15-20 campaniform sensillae is described on the base of the stylus of the endophytic ovipositor of Odonata. It is hypothesised that two symmetric styli equipped with this number of sensillae can function as a mechanosensory organ responsible for control of precise egg positioning in plant stems during oviposition. In laboratory experiments with females of damselflies Lestes sponsa and Lestes barbarus (Lestidae), it was demonstrated that the distance between laid eggs is not dependent on the presence of styli. Removal of styli from both sides did not influence a shift of oviposition to one side. Females with one removed stylus shifted the clutch line in the opposite direction toward the removed stylus. Additionally, removal of styli influenced positions of single eggs in egg sets, and disturbed the capacity for complex oviposition. Thus, both morphological and experimental data support the hypothesis that styli participate in the control of egg line and egg patterning in the clutch.