Among the conspicuous insects which attract the attention of even non-entomologists, there are few more interesting in their structure and habits, as well as in their relations to other groups, than the large “longsting” ichneumons with their long triple “tails.” Our two largest species belong to the genus Rhyssa (of the Hymenoptera), and as, so far as I am aware, no accounts of them have yet been published in the Entomologist, a brief description of their appearance and habits may not be undesirable.

They may be easily distinguished from their relatives (often their victims), the “horn-tails”—Uroceridæ—as they are much more slender in body and appendages. The female, readily determined by the extraordinary development of the ovipositor, has the abdomen stouter than that of the male, with the posterior segments dilated and curved under, and bearing the ovipositor, which is constructed essentially of the same parts as is that of a “horn-tail,” only that they are greatly lengthened.