Rail — The Biology of Stagmomantis Carolina . 3 



pleasant. The two pairs of hind legs are used for carry- 

 ing the body, while these are held high in the air, ever 

 ready to pounce npon some unheeding prey. 



The front coxa is so much enlarged as frequently to be 

 mistaken for the femur (PL XVIII, Fig. 1) ; the femur and 

 tibia are fully supplied with spines, and the five- jointed 

 tarsus is comparatively small. The double row of spines 

 on both femur and tibia are immovable; in addition to 

 these we find in the adults of both sexes three spines, 

 which are movable, located in the middle of the femur and 

 between the two rows, as indicated in PI. XVIII, Fig. 1, 

 point X. When the tibia is folded against the femur, 

 the large, curved spine at the end of the former fits 

 nicely into the groove of the latter just behind these three 

 movable spines, while these bend nicely inward. This 

 modification is of great advantage to the insect in holding 

 prey. How some of the spines first became movable, and 

 these situated just were they would be of most use, while 

 the others remained inflexible, can be explained most 

 readily, it seems to me, by Natural Selection. This insect 

 has been described and re-described and has had at least 

 eight different names, but nowhere in the literature is 

 mention made of these three spines which are movable. 

 Evidently the descriptions were made from dead mate- 

 rial; this show^s the distinct advantage of working with 

 living animals. 



This high modification of the forelegs is correlated with 

 a similarly modified prothorax (see PL XVIII. Fig. 1). 

 It will be seen that the forelegs are attached to this part. 

 How this correlation came about remains a problem of 

 interest. It must be that Natural Selection again, while 

 modifying the appendages to be of use to the insect for 

 long reaching and powerful grasping, harmoniously 

 modified the part that carries them as well. It would 

 certainly be impossible for such an enormous pair of legs 

 to be appended to the usual Orthopteran thorax. On the 

 other hand, what use would economical Nature find in 

 enlarging a part which carries only simple legs, such as 



