Professor Josef Mik, in the September number of the Wiener Entomologische Zeitung (pp. 215-221, pl. iii), gives a most interesting account of the life history of the curious Proctotrupid, Gonatopus pilosus Thoms., which has not before been thoroughly understood. Ferris, in his "Nouvelles excursions dans les grandes Landes," tells how, from cocoons of parasitic larvae on Athysanus maritima (a Cicadellid) he bred Gonatopus pedestris, but this he considered a secondary parasite, from the fact that it issued from an inner cocoon. It appears from the observations of Mik, however, that it was in all probability a primary parasite, as with the species studied by the latter (G. pilosus) the larva spins both an outer and an inner cocoon. The larva of Gonatopus pilosus is an external parasite upon the Cicadellid Deltocephalus xanthoneurus Fieb. The eggs are laid in June or July, and the larvae, attaching themselves at the junction of two abdominal segments, feed upon the juices of their host. But one parasite is found upon a single Cicadellid, and it occasionally shifts its position from one part of the abdomen to another.
Leaving its host in September, it spins a delicate double cocoon in which it remains all winter in the larva state, transforming to pupa in May, and issuing as an imago in June.
It will be remembered that the female in the genus Gonatopus is furnished with a very remarkable modification of the claws of the front tarsi, which are very strongly developed, and differ somewhat in shape in the different species. It has usually been supposed that these claws were for the purpose of grasping prey, but Professor Mik offers the more satisfactory explanation that they are for the purpose of grasping the Cicadellids, and holding them during the act of oviposition.
It is interesting to note that there is in the collection of the Department of Agriculture a specimen of Amphiscepa bivittata Say, which bears, in the position described above, a parasitic larva similar to that described by Mik. It left its victim and spun a white cocoon, but we failed to rear the imago. It is probably the larva of a Gonatopus, and possibly that of the only described American species of the genus, Gonatopus contortulus Patton (Can. Ent., xi p. 64).