300 KELLOGG AND BELL 



tion or voluntary self-mutilation by the throwing off of legs or 

 parts of legs by the insects themselves, rarely regenerated five, 

 the normal number of tarsal segments, but usually only three 

 or four, thus creating a variation by regeneration. 



It is interesting and puzzling to contemplate the curious con- 

 ditions of these regenerative phenomena in Blattids and Phas- 

 mids. If having 5-segmented feet is an advantage to these 

 insects (seized on and fixed by natural selection) and the capacity 

 to regenerate feet after mutilation is an advantage, also fixed by 

 natural selection, why should regenerated feet, as long, as 

 strong, and apparently in every way as effective as 5-seg- 

 mented feet, always be 4-segmented? This is a curious sort 

 of regularly recurring discontinuous variation dependent on 

 some stimulus connected with mutilation and regeneration. 



Variation (Absent) in Number of Tarsal Segments of Largus 

 cincta, Anabrus simplex, Eleodes sp., and Melanoplus femur- 

 rubrum. — A lot of 150 adult individuals of Largus cinctus^ 

 a sucking bug of the family Pyrrhocoridas, collected from 

 two adjoining bushes of Baccharis on the campus of Stanford 

 University, at one time, was examined for variation in number 

 of tarsal segments. The insect has an incomplete metamorpho- 

 sis. The normal tarsus is 3-segmented in all feet. No variation 

 from this number was found. 



A lot of 45 adult individuals (17 males, 28 females) of Anab- 

 rus simplex (western cricket), collected one day at Weiser, 

 Idaho, was examined for variation in number of tarsal seg- 

 ments. The insect has an incomplete metamorphosis. The 

 normal number of tarsal segments in all feet is four. No 

 variation was found. 



A lot of 123 adult individuals of Elcodcs sp. (darkling ground 

 beetle) collected at various times and localities in the vicinity of 

 Stanford University was examined for variation in the number 

 of tarsal segments. The insect has a complete metamorphosis. 

 The normal number of tarsal segments is four in the hind feet 

 and five in the fore and middle feet. No variation was found. 



A lot of 105 adult individuals (60 females, 45 males) of 

 Melanoplus fcmur-ruhruin, the red-legged locust, collected at 

 Ithaca, N. Y., in the summer of 1899, was examined for 



