Anachrysis male (Hymenoptera: Chrysididae: Amiseginae)
By way of introduction, in zoology the suffix “-idae” indicates a family name while “-inae” indicates a sub-family name. To continue, of the 4 sub-families that comprise the wasp family Chrysididae, the Chrysidinae are far and away the most species-rich and visually stunning. Even casual observers of flying insects will recognize them as jewel wasps while those knowing something about their biology and reproductive behaviour will recognize them as cuckoo wasps. The species we are interested in this week is, in fact, a chrysidid wasp, but is neither glamourous nor strange looking. And its reproductive strategy has nothing to do with stealing a meal intended for another, as do the chrysidine cuckoo wasps. Rather, the Amiseginae wasps, of which Anachrysis the species of the week is a member, are parasitoids of insect eggs. And not just any eggs, but those of the iconic Phasmatodea (the stick insects). The world’s longest insect, at over 62 cm, is a species of stick insect and, although formidable looking, all stick insects are phytophagous and of absolutely no threat to animals (not even the human kind). They are capable of regrowing lost legs and some females are facultatively parthenogenic. Our parasitoid, Anachrysis sp., isn’t able to perform such magic but they are, nonetheless, quite interesting. Female Amiseginae wasps inject a single egg into an egg of the stick insect. Inside the host egg the parasitoid hatches and kills the developing host embryo, feeding on the latter and any other egg contents. Until very recently species of Amiseginae were unknown from Eastern Africa, but we have now collected males and females of two amisegine genera from forests and woodlands in eastern Kenya. These include a new sexually dimorphic species of Mahinda (the males can fly but females lack wings) collected in montane forests in the Taita hills. The genus Mahinda was previously known only from south Asia. A different, and somewhat showy, species of the amisegine genus Anachrysis was collected in dry savanna woodland at lower elevations (ca. 600 m ASL) in several areas of eastern Kenya. It is this species of Anachrysis that is featured this week, along with an image of a giant African stick insect (red arrow) and its human friend, for scale.
Credits: Dr Robert Copeland