Insect of the week: 14 August 2023

Xyphorachidia (Hymenoptera: Chacididae): Haltichellinae

In 1951 J.R. Steffan described an insect collected in Senegal by the French entomologist J. Vuillet. Steffan considered the specimen different enough from other Chalcididae that he erected a new genus for it, Xyphorachidia; Xyphorachidia dentata being the type species of the new genus. In his paper Steffan did not provide an explanation for the name he chose for the genus (its etymology). Xypho (or Xipho) means “sword” in Greek and rachis, in zoology, means “spine” or “shaft”. The feature to which the genus name refers is the long, pointed extension of the scutellum, looking much like a sword as the scientific name suggests. In most wasps the scutellum is more or less flush with the first part of the abdomen. In the case of Xyphorachidia the scutellum extends markedly over the basal segments of the abdomen. This feature is hard to miss, and it really does look much like a sword. So, a good choice of names Mr. Steffan.

A few years ago we collected 4 specimens of a second species of the genus while sampling in a Kenyan coastal forest. This was great because not only was the species new, it extended the distribution of the genus trans-continentally; some 6000 kilometres from Senegal to Kenya! Unfortunately, all the Kenyan specimens were males. Why unfortunately? The publication of a new species where both sexes are described together is much preferred because it will account for any sex-related differences within the species (Sexual dimorphism is common in the insect world and differences between the sexes of the same species are sometimes extreme). It is not uncommon for a species to have been described twice from collections that included only one of the sexes. So, we set that project aside, hoping to collect the female. Which happened just a month ago. One of our technicians brought me a specimen collected in another coastal forest and it was a female. Hoorah! Now hold on a minute. The specimen in the petri dish was a Xyphorachidia all right – but it was clearly a different species than both Steffan’s X. dentata and our other coastal forest species. We are patient and wait for the specimens that will complete our project on not one but two new species.

Attached is an image of the recently collected specimen, our nameless, but formidable  insect of the week.


Credits: Dr Robert Copeland