2. EPIGASTRIUM (the _Epigastrium_). The first intire ventral segment[1116]. It includes the _Mucro_ and _Tympana_.
A MUCRO (the _Mucro_). The central posterior point of the _Epigastrium_ observable in many of the Orders, which reposes between the posterior legs; and, according to M. Chabrier, is useful to the insect during flight[1117].
B TYMPANA (the _Drums_). Two deep cavities, containing a complex machinery on each side of the _Epigastrium_ in male _Tettigoniæ_, which are the instruments of sound[1118].
3. SEGMENTA VENTRALIA (the _Ventral Segments_). Transverse sections of the belly[1119]. In Elytrophorous insects they are usually of a firmer consistence than those of the back. They include the _Spiracula Ventralia_.
A SPIRACULA VENTRALIA (the _Ventral Spiracles_).--Breathing-pores observable in some genera in the intermediate ventral segments, one on each side[1120]. Ex. _Dynastes Aloeus_, &c.
4. ELASTES (the _Elastes_). The elastic organs on the ventral segments of _Machilis polypoda_ which assist this insect in leaping.
iii. PETIOLUS (the _Footstalk_). A slender part by which the abdomen of many _Hymenoptera_ is united to the trunk, in some genera very long, in others very short, and in others wanting[1121]. It includes the _Funiculus_, _Foramen_, _Squama_, and _Nodus_.
1. FUNICULUS (the _Funiculus_). A small cartilaginous _cord_, passing through a minute orifice of the _Postfrænum_, just above the point where the footstalk is fixed, to an opposite hole above it, which enables the animal the better to elevate or drop the abdomen[1122].
2. FORAMEN (the _Foramen_). The orifice in the abdomen, through which the above cord passes[1123].
3. SQUAMA (the _Scale_). A vertical flat scale, observable on the footstalk of the genus _Formica_, &c.[1124]
4. NODI (the _Knots_). One or more subrotund protuberances of the footstalk in the genus _Myrmica_[1125].
iv. CAUDA (the _Tail_). Where the abdomen grows suddenly slenderer, and terminates in a long jointed tail, as in _Scorpio_ and _Panorpa_[1126]. It includes the Centris.
1. CENTRIS (the _Centris_). The last inflated joint of the tail, terminating in the _Sting_.
v. ANUS (the _Anus_). The termination of the abdomen, consisting of the two last segments. It includes the _Podex_, _Hypopygium_, _Culus_, _Ovipositor_, and _Appendices_.