May, iQOt] 



PSYCHE. 



197 



and shapes that side into the form and or It-ss of preparation, the butterliy is 



protection of a cell. once more upon the wing — a stranded 



The chrysalis state is assumed in relic of the great Ice Age, like the alpine 



June, and lasts two weeks or more, sandwort, Arcnaria grocnlandka, whose 



and then again, after two years more honeyed sweets it now robs. 



VARIATION IN TRIDACTYLUS. 



BY A. P. MORSE, WELLESLEY, MASS. 



Tiiilactyhis is a genus of small, fosso- 

 rial crickets, allied in structure and hab- 

 its to Gryllotalpa, the mole-cricket, and 

 differing most noticeably from that genus, 

 among several things, in being smaller 

 in size and possessing remarkable salta- 

 tory powers. 



Representatives of the genus occur 

 over the greater part, at least, of the 

 United States, and range in size from 

 six to twelve millimeters in length when 

 adult. They frequent the margins of 

 streams and ponds, burrowing in the 

 sandy loam of the banks and shores, 

 and may be secured, when a station is 

 discovered, by sweeping rapidly ju.st 

 above the ground with a net of cheese- 

 cloth or other close-meshed material. 

 Owing to their alertness, activity, and 

 leaping mode of progression close obser- 

 vations of their habits are exceedingly 

 difficult to make out-of-doors and but 

 little is known regarding them. Whether 

 confinement would secure satisfactory 

 results remains to be learned, but it is 

 hoped that some one having an oppor- 

 tunity to do so will make the attempt 

 and if possible discover the special func- 



tion of the remarkably modified anterior 

 tibiae of the male in certain species and 

 the significance of the variation noted 

 below. 



While collecting on Nantucket Island 

 late in the afternoon of July 12, 1900, I 

 found a locality for Tridactylus on the 

 shore of a small pond and captured 

 several examples of both sexes. On the 

 following day additional specimens were 

 secured in the same place and about an 

 adjoining pond. On my return home, 

 examination after mounting disclosed an 

 interesting state of affairs. 



The 52 specimens taken on the two 

 successive days in this one locality con- 

 sist of one immature, 18 females, and 

 T,T, males. These exhibit no essential 

 difference in color, size or markings 



o 



leading one to infer the presence of two 

 species, nor do the female examples dif- 

 fer in structural details. A close exam- 

 ination of the males, however, reveals a 

 singular variation in the structure of the 

 anterior tibiae. In about one third of 

 the males the form is the same as that 

 of the female (Fig. i ), — more or less 

 irregularly ovate in outline, terminating 



