EXTERNAL ANATOMY OF INSECTS. 389 



Breathing-pores observable in some genera in the 

 intermediate ventral segments, one on each side a . 

 Ex. Dynasles 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 b . It includes the Fu- 

 niculus, Foramen, Squama, and Nodus. 



1. Funiculus (the Funiculus). A small cartilaginous 

 cord, passing through a minute orifice of the Post- 

 frcenum, 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 c . 



2> Foramen (the Foramen). The orifice in the abdo- 

 men, through which the above cord passes d . 



3. Squama (the Scale). A vertical flat scale, observable 



on the footstalk of the genus Formica, &c. e 



4. Nodi (the Ktwts). One or more subrotund protube- 



rances of the footstalk in the genus Myrmica f . 



iv, Cauda (the Tail). Where the abdomen grows sud- 

 denly slenderer, and terminates in a long jointed 

 tail, as in Scorpio and Panorpa s . It includes the 

 Centris. 



1. Centris (the Centris). The last inflated joint of the 

 tail, terminating in the Sting. 



» Plate VIII. Fig. 9. D' . b Plate IX. Fig. 17, 18. C. 



c Ibid. F 1G . 13. F'. (1 Ibid. G. 



e Ibid. Fig. 17. //'. ' Ibid. Fig. 18. 7'. 



« Plate XV. Fig. 12. Z>. 



