INSECTS 259 



I do not consider this evidence by any means sufficient ; the 

 smallest males may not be completely sterile, just as worker 

 bees are not always perfectly sterile. The question is whether 

 there is any constant difference in the size and development 

 of the sexual organs in the well- developed and the ill- 

 developed males. I cannot discover that any one has properly 

 investigated the subject. 



Stridulating organs in Coleoptera have been discussed at 

 length by Darwin, and he shows that only in a few species 

 are they confined to one sex. There is no difficulty, once 

 admitting that mechanical stimulation produces a hereditary 

 effect on growth and development, in understanding how 

 special stridulating organs have been evolved. Darwin sup- 

 poses that "originally various beetles made a shuffling or 

 hissing noise by the rubbing together of any hard and rough 

 parts of their bodies ; and that from the noise thus produced 

 being in some way useful, the rough surfaces were gradually 

 developed into regular stridulating organs." To this conclu- 

 sion I have no objection to offer, provided that it is under- 

 stood that the gradual development was the consequence 

 of the friction, and not due to selection from spontaneous 

 variations. 



In many Malacodermata we find a sexual dimorphism 

 similar to that which occurs in many moths, the females 

 having lost their wings, and being otherwise degenerate. This 

 occurs in the common glow-worm, Zampyris noctiluca, and 

 species allied to it. The males have ample wings under 

 their elytra, and very large eyes. The female has smaller 

 eyes and neither elytra nor wings ; her body is flat, soft, and 

 broad, and in fact resembles the larva from which she is 

 developed, except that she possesses the ordinary femur, tibia, 

 and five-jointed tarsi to the legs, eleven- jointed antennae, and 

 a broad, flat, semicircular thorax. It is difficult to perceive 

 in what way the degeneracy of the female is to be explained 



