INSECTS AND ARACHNID A 



of this is furnished by the gad-fly (Tabanus), whose ovipositor is 

 composed of several joints, capable of being drawn together or 

 extended like those of a telescope, and is terminated by boring 

 instruments ; and the egg being conveyed by its means, not only 

 into but through the integument of the ox, so as to be imbedded in 

 the tissue beneath, a peculiar kind of inflammation is set up there, 

 which (as in the analogous case of the gall-fly) for.ms a nidus appro- 

 priate both to the protection and to the nutrition of the larva. Other 

 insects which deposit their eggs in the ground, such as the locusts, 

 have their ovipositors so shaped as to answer for digging holes for 

 their reception. The preparations which serve to display the fore- 



FIG. 747. Various eggs, chiefly of the Mallopliaga (Anoplura). 



going parts are best seen when mounted in balsam, save in the 



of the muscles and poison-apparatus of the sting, which are better 



preserved in fluid or in glycerin jelly. 



The sexual organs of insects furnish numerous objects of extreme 

 interest to the anatomist and physiologist ; but as an account of 

 them would be unsuitable to the present work, a reference to n 

 copious source of information respecting one of their most curious 

 features, and to a list of the species that afford good illustrations, 

 must here suffice. 1 The eggs of not only the class Insecta, but of 



1 See the memoirs of M. Lacaze-Duthiers, ' Sur 1'Armure Genitale des Insectes,' in 

 Ann. des Sci. Nat. ser. iii. Zool. tomes xii. xiv. xvii. xviii. xix. ; and M. Ch. Robin's 



