No abstract

The effects of natural enemy releases on conservation genetics within ecosystems are rarely considered. Diadegma semiclausum (Hellen) (Hymenoptera: Ichneumonidae) was introduced and continues to be released for biological control of diamondback moth in Japan. Diadegma semiclausum and indigenous Diadegma fenestrale (Holmgren) (Hymenoptera: Ichneumonidae) share geographic ranges and hosts, and produce offspring when mated under laboratory conditions. We used DNA to examine whether offspring from inter-specific one-way parental crosses (D. semiclausum / and D. fenestrale ?) were hybrid, as some Hymenoptera (e.g. Aphidius colemani Viereck (Hymenoptera: Braconidae)) exhibit thelytokous reproduction by gynogenesis. Molecular analyses revealed offspring mtDNA (COI) is maternally inherited, as expected, but rRNA (ITS-2) originates from both parents. Should similar hybridization occur in the field beyond the F1 generation, genetic mixing is a possible consequence that may influence biological control efficacy or pollute native population genetics.

No abstract

The present study reports the oviposition behavior of the ant parasitoid wasp, Ghilaromma orientalis, on an undescribed ant species from Lasius fuliginosus species group in Japan, illustrated by clear photographs. Previously, the oviposition behavior in the subfamily Hybrizontinae had been limited to species hovering on an ant trail and attacking larvae carried by worker ants. In contrast, in G. orientalis, whose oviposition behavior had not been reported to date, the wasp hung on the grass growing along the ants’ trail by its hind legs with its head down, and when workers with larvae pass by, directed its abdomen toward the larvae with its hind legs remaining on the grass. Our findings suggest that the subfamily Hybrizontinae employs two host-searching strategies—an active strategy previously known and the ambush-type host-searching strategy employed by G. orientalis. The ambush-type strategy affords G. orientalis the advantage of laying eggs in a narrow environment where wasps cannot fly without being noticed by ants. Moreover, by avoiding detection through ambush tactics, wasps are increasing their chance for attack, as ants continue to transport their larvae. However, the search range of wasps is reduced, which may limit the opportunities for parasitization. Additionally, while Lasius nipponensis has been observed as the sole known host of G. orientalis, the oviposition behavior has now been observed in an undescribed species of L. fuliginosus group, suggesting that G. orientalis may have a subgenus-specific host range.