ITS OUTER SKELETON. 59 



the metasternum, and its short basal piece is attached between 

 the lateral halves of that plate. Behind the mesosternum is a 

 somewhat slighter prop, the medi-furea. A third piece of similar 

 nature (the ante-furca), which is well developed in some Insects 

 e.g., in Ants is apparently wanting in the Cockroach, though 

 there is a transverse oval plate behind the prosternum, which* 

 may be a rudimentary furca. 



Fig. 27 shows two conical processes which lie in the middle 

 line of the ventral surface of the thorax, one in front of the 

 metasternum, the other in front of the mesosternum. These 

 are the thoracic pits, tubular apodemata, serving for the 

 insertion of muscles. The occurrence of stink-glands in 

 the thorax of Hemiptera,* and of so-called poison-glands 

 in the thorax of Solpuga, led us to look for glands in 

 connection with these processes, but we have found none. 



Thoracic Appendages. Legs; Wings. 



Three pairs of legs are attached to the thoracic segments ; 

 they regularly increase in size from the first to the third, but 

 hardly differ except in size ; the peculiar modifications which 

 affect the fore pair in predatory and burrowing Orthoptera 

 (Mantis, Gryllotalpa), and the third pair in leaping Orthoptera 

 (Grasshoppers, &c.), being absent in the cursorial Blattina. Each 

 leg is divided into the five segments usual in Insects (see fig. 28). 

 The coxa is broad and flattened. The trochanter is a small piece 

 obliquely and almost immovably attached to the proximal end 

 of the femur, on its inner side. The femur is nearly straight 

 and narrowed at both ends ; along its inner border, in the 

 position occupied by the stridulating apparatus of the hind leg 

 of the Grasshoppers, is a shallow longitudinal groove, fringed 

 by stiff bristles. The tibia is shorter than the femur in the fore 

 leg, of nearly the same length in the middle leg, and longer in 

 the hind leg ; it is armed with numerous stiff spines directed 

 towards the free end of the limb. There are usually reckoned 

 five joints in the tarsus, which regularly diminish in length, 

 except that the last joint is as long as the second. All the 



* Also in Phasmidce (see Scudder, Psyche, Vol. I., p. 137). 



