S12 MOTIONS OF INSECTS. 



organs, before concealed, instantly appear, and tli^ 

 laminae which terminate them being separated from 

 each other as widely as possible, they begin their march. 

 They employ their antenna?, however, not as feelers 

 to explore surrounding- objects, — their palpi being ra- 

 ther used for that purpose,— but, it should seem, merely 

 to receive vibrations, or impressions from the atmo- 

 sphere, to which these laminae, especially in tlie male 

 cockchafers (3Ielolonthce, F.), present a considerable 

 surface. Yet insects that have filiform or setaceous an- 

 tennae appear often to use them for exploring. When 

 the turnip-beetle {Ilaliica oleracea, F.) Avalks, its an- 

 tennae are alternately elevated and depressed. — The 

 same thing takes place with some woodlice (Oniscidce), 

 which use them as tactors, touching the surface on each 

 side with them, as they go along. This is not however 

 constantly the use of this kind of antennae ; for I have 

 observed that Cantharis livida, L. — a narrow beetle 

 with soft elytra, common in flowers, — when it walks 

 vibrates its setaceous antennae very briskly, but does 

 not explore the surface with them. The parasitic tribes 

 of Ichneumonidce, especially the minute ones, when 

 they move vibrate these organs most intensely, and 

 probably by them discover the insect to which the law 

 of their nature ordains that they should commit their 

 eggs ; some even using them to explore the deep holes 

 in which a grub, the appropriate food of their larva, 

 lurks ''. But upon this subject I shall have occasion to 

 enlarge wlien I treat of the senses of insects. — Antennse 

 are sometimes used as legs, A gnat-like kind of bug 

 (Gerris vagabundus, F.) has very short anterior legs, 



* MUrsham in Linn. Trans, ill. 26 — 



