II] 



EXTERNAL FEATURES AND SKELETON 



27 



used in the act of capturing prey on the wing. A difference of 

 opinion prevails on this point. The difficulty of making direct 

 observations is obvious, and has not so far been satisfactorily 

 overcome. 



Each leg consists of five segments or 

 joints, called (from the base outwards) coxa, 

 trochanter, femur, tibia and tarsus. There is 

 no trochantine. The coxa (ex) is a short 

 truncated cone, with its rounded base inserted 

 into a large hollow, the acetabulum, situated 

 in the side of the sternum, close to the 

 pleurum. The bases of insertion of the legs 

 of the Dragonfly are very closely approxi- 

 mated, particularly in the cases of the middle 

 and hind-legs (fig. 1 B). The trochanter (tr) is 

 a short and rather slender joint, having a very 

 short upper surface, so that its distal end runs 

 obliquely downwards, and the articulation 

 with the femur is correspondingly modified. 

 A transverse constriction divides the tro- 

 chanter into a shorter basal and a longer 

 distal portion. An armature of short thick 

 blunt teeth or tubercles may be present. 

 The femur (fm) is the strongest joint in the 

 leg. It is a cylindrical, fairly stout, long 

 joint, strongly armed with at least two rows 

 of spines or tubercles. The tibia (tb) is generally 

 somewhat longer, and much slenderer than 

 the femur; it also is armed with two rows of spines, varying 

 greatly in number, size, and arrangement. The tarsus (ts) is the 

 short slender terminal segment. In all living Dragonflies, it con- 

 sists of three joints, of which the basal is the shortest, the distal 

 the longest. In the fossil genus Tarsophlebia (fig. 158) there were 

 four joints, the basal being the longest. The joints of the tarsus 

 are armed with small, closely-set spines continuing the lines of the 

 tibial armature. The tarsus ends distally in a pair of strong 

 diverging claws (cl), each of which usually bears a well-developed 

 inferior tooth. Between the bases of the claws there can be 



Fore-leg 

 of Hemicordulia tau 

 Selys, (J (x 5). shew- 

 ing tibial keel (tbc). 

 B. Part of hind-leg of 

 Platycnemis pennipes 

 Pallas, $ ( x 10), shew- 

 ing dilated tibia, cl 

 claws; ex coxa; fm 

 femur ; tb tibia ; tr tro- 

 chanter ; ts tarsus. 

 Original. 



