26 THE IMAGO [CH. 



acetabulum. In the case of the metapleural (which lies along 

 the second lateral suture, Is 2 ), there is an additional branch, the 

 peristigmatic (pst), running to the metastigma (St). The inter- 

 pleura] (ip) is weakly developed, lying along the first lateral 

 suture (Isj). The sternal apodemes are known as the furca (/2,/a) 

 and prefurca (pf 2) pf 3 ). The furca develops a slender posterior 

 process (pr z , / 3 ') which in the case of the mesothoracic apodeme 

 serves to connect the mesosternum with the metasternum. A 

 similar process (pr-^ connects the mesosternum with the pro 

 sternum. Anteriorly the furca gives off a large flattened process 

 or squame (tn 1} tn 2 ) which becomes highly specialized to serve as 

 the tendon of attachment for the great elevator wing-muscle. 

 The prefurca likewise develops a squame (sq 2 , sq s ) which is less 

 highly specialized in form, but serves as the tendon of attachment 

 for the anterior depressor wing-muscle. The sternal apodemes are 

 so bent inwards towards the middle line that they almost meet 

 along their free edges, isolating below them a small canal of flattened 

 triangular section, the neural canal (fig. 8 B). The ventral nerve 

 cord runs through this canal, which serves as a protection to it, 

 and isolates it from all the rest of the thoracic organs. 



The Appendages of the Thorax. 



The Wings are dealt with in chap. in. 



The Legs (fig. 9). All Dragonflies possess the full number of 

 legs, viz. three pairs, one pair to each thoracic segment.. Though 

 short in comparison with the size of the body, as well as with 

 their size in the larva, the legs of the Dragonfly are of con- 

 siderable strength, and are strongly armed. Their position close 

 behind the mouth renders them unfit for walking, though they 

 serve very well for climbing, when that mode of progress is 

 required. By the use of its legs, a Dragonfly can quickly 

 orientate its position, so as to interpose the stem of a reed, or 

 a small twig, between itself and an approaching enemy. During 

 flight, all three pairs of legs are carried folded close up under 

 the thorax. The first two pairs at least are able to hold the 

 prey during flight, while the mouth-parts examine and chew it 

 up. It seems very probable that the fore-legs at any rate are 



