STUDIES OF VARIATION IN INSECTS 



301 



variation in the number of tarsal segments. The locust has an 

 incomplete metamorphosis. The normal number of tarsal seg- 

 ments, in all feet, is three, the first (basal) obviously being 

 composed of the fused first three segments of a 5 -segmented 

 foot. Reversionary variation would be manifest in any in- 

 crease in the number of segments, particularly, a breaking up 

 of the first or basal compound segment into two or three dis- 

 tinct segments. In the 105 individuals (= 630 feet) examined 

 no tarsus was found showing really any fewer or any more 

 than three segments. In one female and in two males, one, 

 or two, hind feet showed some constriction of the first (basal) 

 segment, weakl}^ indicating a subdivision into two parts. 



Variation in Number of Tibial Spines of Melanoplus femur- 

 rubrum (Red-legged Locust). — The locusts, or grass-hoppers, 

 are insects with incomplete metamorphosis, the just-hatched 



Fig. 61. Tl.e red-legged locust, Melanoplus fcjiiur-nibrum, and enlarged 

 hind tibia showing inner («') and outer (o) rows of spines. 



young resembling in all important structural characters, ex- 

 cept for the absence of wings, the adults. The larval and 

 adult legs are identical structures. On the ventral (hinder 

 aspect) of the tibiae of the large posterior leaping legs are two 

 rows or series of small but distinct spines, one along the outer 

 edge, the other along the inner (fig. 61 ) . The number of spines 

 in this series has been used as a diagnostic character of the 

 various species of the large genus Melanoplus . 



A lot of 89 adult individuals (50 females, 39 males) of the 

 red-legged locust, Melanoplus femit7--rnhnim^ collected at Ith- 

 aca, N. Y., in a brief time period, was examined to determine 



Proc. Wash. Acad. Sci., Dec, 1904. 



