HYMENOPTERA. Ill 



agiis which dilates into a thin-walled sucking stomach," which 

 in the ApiaricB and VespidcB may be simply a lateral fold, 

 or, as in many Crahronidoi^ "attached solely by a short and 

 narrow peduncle." In Formica, Gy nips ^ Leucospis, and Xyp)liid- 

 ria there is a globular uncurved callous gizzard, which is en- 

 veloped by the base of the stomach, according to Siebold, who 

 also states that "those Hymenoptera which are engaged during 

 a long and active life in labors for the raising and support of 

 their young, have a pretty long and flemious stomach and in- 

 testine, and the first has, usually, many constrictions ; " while 

 the Cynipidce, Ich7ieumonid(E, and Tentliredinidce , 

 which take no care of their young, have only a short small 

 stomach and intestine. The salivary glands consist of two 

 rather short ramified tufts, often contained entirely in the head. 



The tracheae consist, as in other insects, of two main branches, 

 from which numerous transverse anastomosing branches are 

 given off, with numerous vesicular dilatations. Two such vesi- 

 cles of immense volume are situated at the base of the abdo- 

 men, which according to Hunter and Newport "serve chiefly 

 to enable the insect to alter its specific gravity at pleasure dur- 

 ing flight, and thus diminish the muscular exertion required 

 during these movements." 



The urinary vessels are very numerous in the Hj^menoptera ; 

 they are usually short and surround the pylorus in numbers of 

 from twent}^ to one hundred and fift3^ 



The two poison glands (Fig. 54, li,g) are composed of long 

 ramose tubes, resembling the salivary glands in their minute 

 structure. The poison is poured from these into a pj^iform 

 sac lodged near the base of the sting, which is provided with a 

 peculiar muscular apparatus for its sudden extension and with- 

 drawal. The poison, in the Ants, Bees, and Wasps, consists, 

 according to Will, of "formic acid, and a whitish, fatty, shafp 

 residuum, the former being the poisonous substance." (Bur- 

 nett.) 



Whether the wax-secreting apparatus consists of special 

 glands (as Milne-Edwards supposes) or not, as Dufour, Siebold, 

 and others contend, is not yet a settled question. Siebold, the 

 eminent German physiologist, from whose work on the anatomy 

 of Invertebrata we have drawn so largely, suggests that the 



