696 EXTERNAL ANATOMY OF INSECTS. 



form an angle with each other and turn upwards, the tibia 

 having an external oblique cavity to permit this ; but the 

 insects most remarkable for packing close their legs are 

 those carnivorous genera Dermestes, Anthrenus, Byrrhus, 

 &c. In the last-mentioned genus there are cavities in 

 the under side of the trunk, in each division of the 

 breast, and at the base of the abdomen, to receive the 

 legs when folded; the coxa have also a cavity to receive 

 the base of the thigh. In the anterior legs this last part 

 has a longitudinal one on its upper side, and in the 

 four posterior on the under, which receives the tibia, 

 which at the inner edge are straight, and at the outer 

 curvilinear, and the tarsi are turned up and received by 

 the concave part, on the anterior side of the Jirst pair 

 and the posterior side of the two last of the tibia, so as 

 to lie between it and the body : when the legs are close 

 packed, the animal looks almost as if it had none. I 

 have observed that when Dytisci repose on the w r ater, 

 the posterior legs are turned up and laid over the elytra, 

 and curved towards the head. 



vi. Pectines. I must next say a few words upon a re- 

 markable organ, which seems in some degree supplemen- 

 tary to the legs, by which the Creator has distinguished 

 the genus Scorpio, called from its parallel teeth, set in a 

 back, their pecten or comb a . This back consists of two 

 or more articulations, is attached by its anterior extremity 

 to the 'sides of the posterior piece of the mesostethium, 

 and is marked by a longitudinal furrow or channel. The 

 teeth, which vary in number in the different species, and 



a Plate XXVU. Fig. 50. 



