Insect of the week: 18 September 2023

Insect of the week (42), Myrmecoclytus orientalis Adlbauer (Cerambycidae: Lamiinae: Acanthocinini)

Okay. Enough of these little wasps for now. Not all tiny insects are wasps. Let’s consider a beetle for a change, in the family Cerambycidae (common name longhorn beetles, from the Greek Greek kerambyx, a horned beetle). Worldwide, cerambycids number over 36,000 species that are usually mid to gigantic in size (with some of the largest insects in the world). However, you might guess that a family with so many species must have a small one or two, and you’d be right. With specimens as short as 2.2 mm in length our insect of the week, Myrmecoclytus orientalis, is a contender for the title of the world’s smallest cerambycid. Alas, it appears that Cyrtinus pygmaea, found in North America, may hold the record with specimens ranging from 2 to 3 mm (hats off to them). It’s all relative though, Myrmecoclytus and Cyrtinus are giants in comparison to the world’s smallest free-living (i.e. non-parasitoid) insect, the beetle Scydosella musawasensis, which measures as little as 325 μ (microns) in length (=0.325 mm).

Myrmecoclytus orientalis was described in 2018 by Karl Adlbauer, the legendary coleopterist, from specimens we collected in coastal Kenya, two from Muhaka forest, including the holotype, and one from Kinondo forest. A single specimen was sampled in Njuki-ini forest at 1471m above sea level, and it was also collected from the Eastern Arc Mountains of Tanzania. The species appears to be associated exclusively with indigenous forest.

Besides the great number of species already described in the family, Cerambycidae species are placed in more than 5300 different genera. These genera are distributed among the 8 subfamilies of longhorn beetles of which Lamiinae are by far most common. Myrmecoclytus is a member of the Lamiinae (common name flat-headed beetles – the head being flattened, with the mouthparts pointing downward (Hypognathous).  Lamiinae species are easily differentiated from the second largest subfamily, the Cerambycinae, the latter being prognathous (mouthparts pointing forward). The genus Myrmecoclytus itself contains 8 species, of which one, Myrmecoclytus natalensis is, like M. orientalis, an Afrotropical endemic. Nothing is known of its biology but larvae of other cerambycids bore in living, woody plants or dead wood, as well as herbaceous plants. Several species are pests of trees.

Credits: Dr Robert Copeland