Stethoconus sp. (Heteroptera: Miridae: Deraeocorinae: Hyaliodini)
Specimens selected for the image of the week have disproportionately favoured those species from orders (e.g. flies, fleas, bees and wasps, butterflies and moths, beetles, etc) that develop holometabolously; that is, their juvenile stages (larvae) do not in the least resemble the adult which they will miraculously become. Such a developmental plan offers a great advantage in that the two stages of a species avoid intraspecific competition for food and space. This is not the case for hemimetabolous species whose larval and adult forms closely resemble each other. Insect orders in which this type of development holds sway include the true bugs, grasshoppers and crickets, mantids, etc., and this week we consider a true bug, Stethoconus sp. Before we do though, a word about the word ’bug’. You’d be hard pressed to come up with a less attractive appellation for such a huge group of species, many of which are quite attractive. A bug is something that annoys you (e.g. ‘he bugs me’), or nefariously invades one’s privacy (“the room was bugged”, or messes up the works (a computer bug) or signifies flu-like symptoms (he’s caught the bug) or to suggest an abnormality of the eyes (bug-eyed). All these have a negative connotation. The name itself sounds harsh (say it aloud). The true bugs need better public relations, starting perhaps with a new common name.
There are but 8 species of Stethoconus worldwide with four native to Africa). The genus gets its name from the cone-like protrusion on its dorsal surface (see image of the lateral view). Curiously, the prefix “Stetho” means “chest” in Greek, when it’s clearly the case that the position of the cone is dorsal, not ventral. The Miridae, the family in which Stethoconus sp. is a member, are by far the most successful of the Hemiptera; the true bugs. There are several common names attached to this family but ‘Leaf bugs’ and ‘plant bugs’ seem to be the most popular. Mirids are everywhere, with 11,000+ described species distributed among no less than 1300 genera. The family has been around a long time. Mirivena robusta, the oldest known fossilized bug, is a Miridae from the mid Jurassic, ca. 175 MYA (Million years ago). Most mirids are plant feeders piercing the outer layers of their prey, either plant or animal and imbibing its phloem or hemolymph with their tubular proboscis. Several species are serious pests of important crops including tea, cotton, cacao, cashews and avocados. However, the genus Stethoconus (and others) is an exception. Species of Stethoconus are predaceous on insects, not plants, and apparently adapted to feed only on lace bugs (family Tingidae). There are several important pest Tingidae that transmit plant viruses. Stethoconus praefectus was recently found on avocado in the new world where it attacks the Avocado lace bug, Pseudacysta perseae. Thus, Stethoconus falls into the category of “farmers’ friends”. Luckily, to date Africa has been fortunate to escape infestation by P. perseae, but given the vast increase in trade and movement of fruits among countries it would not be surprising if it showed up here. If so, S. praefectus would be a potential candidate for targeted introductions into affected areas to aid in biological control of P. perseae. We captured our one specimen of Stethoconus in Kaberua forest in the foothills of Mt. Elgon at 2052 m ASL. This is the 1st record of the genus in Kenya.
Credits: Dr Robert Copeland