Optimizing the application method of entomopathogenic nematode suspension for biological control of large pine weevil Hylobius abietis

Entomopathogenic nematodes (EPNs) are effective against the immature stages of the large pine weevil Hylobius abietis. In three field trials we compared the efficacy of the application method of EPN for weevil suppression below the suggested threshold of 20 weevils per stump: applying the EPN suspension in the top edges of the stumps (‘top’) vs. drenching the soil around stumps (‘standard’). For Steinernema carpocapsae, weevil suppression was below the targeted threshold only when suspension was applied in the standard way (two of the three sites). On the other hand, weevil suppression was provided in all three cases of ‘top’ application of Heterorhabditis downesi suspension, whereas suppression in ‘standard’ application was observed in one site. Percentage parasitism of developing weevils in relation to depth and distance help explain EPN movement post-application. Weevil suppression relative to suggested thresholds can be improved by altering the method of EPN application depending on the nematode species

Divergent mating patterns and a unique mode of external sperm transfer in Zoraptera: an enigmatic group of pterygote insects

A remarkable external sperm transfer is described for the first time in a species of a group of winged insects (Pterygota), the enigmatic Zoraptera. Mating and sperm transfer of two species of the order were examined in detail, documented, and compared with each other and with patterns described for other species belonging to the order. The behavior differs strikingly in Zorotypus impolitus and Zorotypus magnicaudelli. A copula is performed by males and females of the latter, as it is also the case in other zorapteran species and generally in pterygote insects. In striking contrast to this, males of Z. impolitus do not copulate but deposit small (100 μm in diameter) spermatophores externally on the abdomen of the female. Each spermatophore contains only one giant spermatozoon (3 mm long and 3 μm wide), a unique feature in the entire Hexapoda. External sperm transfer in Pterygota is a highly unusual case of evolutionary reversal. The very small relict group Zoraptera displays a uniform general morphology but exhibits very different reproductive structures and patterns of mating behavior. This may be an extreme form of a more general situation in insects, with a specific form of selection resulting in an accelerated rate of evolution in the reproductive system. © 2013 Springer-Verlag Berlin Heidelberg