CH. Ill] THE COCKROACH 89 



movement of the hind-legs : the inner face of the femora 

 of these legs bears, on a ridge projecting inwards, a series 

 of knobs, which are modified hairs. When the femora 

 are moved up and down these knobs strike against a 

 sharp-edged vein which stands out prominently from the 

 outer face of the upper wings, and thus the well-known 

 note is emitted. The auditory organ which enables neigh- 

 bouring grasshoppers to hear the call is situated on the 

 dorsal side of the first abdominal segment, just above the 

 articulation of the hind leg: it consists of a broad slit 

 opening into a cavity with the auditory membrane below. 



Locusts produce their note in a different manner : the 

 left fore-wing has on its inner surface a file which is 

 worked to and fro over a sharp edge on a prominent part 

 of the inner margin of the right fore- wing. The auditory 

 organ, too, is not situated as in grasshoppers, but lies 

 in the upper part of the tibia3 of the front legs. In 

 the crickets each fore-wing has on its under surface 

 a stridulating file, the right as a rule overlapping the left : 

 the auditory organs consist of a pair of cavities on each 

 front leg, a larger on the outer and a smaller on the inner 

 face. Some authorities state that there is yet another 

 pair of auditory organs on the second abdominal segment. 



Reproduction and growth. The breeding season of the 

 cockroach is during the summer months. The spermatozoa 

 of the male are passed into the spermatheca of the female 

 in the course of sexual union, the male obtaining a secure 

 hold upon the female by means of a series of strong hooks 

 and plates surrounding the genital aperture. The ventral 

 portion of the seventh segment of the female is produced 



