This late into autumn most goldenrods (Solidago sp., Asteraceae) have dried up and gone to seed. Last week, however, I found a few small plants in a meadow that still had handfuls of bright yellow nectar-laden flowers. Upon closer inspection I realized I wasn’t the only one to take notice; the flowers were covered with dozens of these tiny parasitoid wasps (Hymenoptera: Ichneumonidae: Tersilochinae).
With winter fast approaching, it seemed unsurprising that so many of these wasps were crowding around some of the last few sources of nectar. The individuals shown here spent most of their time with their faces buried in the flowers, lapping up the sugary food. They emerged only briefly to move from one flower to the next.
Although adults of this subfamily feed on nectar, the larvae are internal parasitoids, predominantly of beetles (Triplehorn and Johnson 2005). A female uses her long, slender ovipositor to lay an egg inside an active host insect. The egg hatches, the larva feeds on the host’s insides, and then eventually emerges as an adult, killing the host. Some species of these wasps target beetles that are pests of crops and trees. Tersilochus conotracheli is a parasitoid of the plum curculio (Coleoptera: Curculionidae: Conotrachelus nenuphar), a significant pest of fruit trees (Triplehorn and Johnson 2005).
Triplehorn, C.A. and N.F. Johnson. 2005. Borror and DeLong’s Introduction to the Study of Insects. Seventh Edition. Thomson Brooks/Cole, Belmont, CA.