320 



PSYCHE. 



[March, igo2 



Achorutcs packardi, var. dentatus, var. n. 

 (Figs. 19-24.) 



In this variety all the superior claws 

 (fig. 19) are unidentate, the mucrones 

 (figs. 20, 21) are one fourth as long as 

 the dentes, slender and laterally lamel- 

 late, the anal spines (fig. 22) are slender, 

 while the stout erect setae are eilher not 

 capitate (fig. 23), or else are obscurely 

 capitate on the posterior part of the 

 abdomen (fig. 24). In all other respects 

 the variety agrees with the typical form. 



Orono, Maine, March 10, 15, May n, 

 F. L. Harvey; Arlington, Massachusetts, 

 April 10, 13, 23, 30, May 23, September 

 10; Ghent, New York, April 13, E. C. 

 Powell (N. Y. State Coll.). 



This variety lives under the loose bark 

 of pine, red maple, and oak trees, especi- 

 ally at the base of the roots, and some- 

 times occurs on snow. It has at least 

 three broods, which mature at intervals 

 of six or seven weeks. 



Dentatns is a seasonal variety of pack- 

 ardi. Young individuals that hatched 

 May 20 from eggs laid by the variety 

 dentatus were not that variety, but were 

 the typical form, with bulbiferous setae, 

 no teeth on the superior claws, and with 

 lamellate mucrones. One of the four 

 specimens from Ghent, N. Y., was the 

 variety dentatus, the others being the 

 typical form. 



This is the first record of seasonal 

 dimorphism among the Collembola, al- 

 though I suspect that certain other spe- 

 cies also assume disguises, according to 

 the season in which they occur. This 



can be proved, however, only by careful 

 breeding e.xperiments, which are difficult 

 to conduct accurately with these insects. 



Achorutcs /larveyi sp. n. 



(Figs. 25-34.) 



Dark indigo blue throughout. Eves (fig. 

 25) sixteen. Postantennal organs (figs. 26, 

 27) of tour elliptical-oval elements. Antennae 

 (fig. 2S) subequal to the head in length, with 

 segments as 10: 13: 13 : 20 ; first two segments 

 subclavate, last two subcylindiical. Body 

 elongate, abdomen subfusiform. Superior 

 claws (fig. 29) slender, tapering, slightly 

 curved, unidentate about one third from the 

 apex ; inferior claws less tlian half as long, 

 basal half suboblong, apical half acicular ; 

 one long tenent hair with bent apex. Manu- 

 brium as long as the rest of the furcula; 

 dentes stout, subcjlindrical. apically broad 

 and rounded, projecting beyond the bases of 

 the mucrones. bearing two rows of teeth 

 (fig. 30), fourteen to twenty-five in number, 

 which are variable in size, and are more or 

 less confluent basally ; five may be much 

 larger than the others (fig. 31), and sometimes 

 no teeth are present; mucrones (fig. 31) one 

 fourth as long as dentes, in profile suboblong, 

 dorsally concave, apically emarginate. Anal 

 spines (figs. 32, 33) two, long (almost as long 

 as a superior claw), slender, feebly curved, 

 upon prominent approximate papillae. Cloth- 

 ing (fig. 34) of numerous curving setae and 

 fewer bowed liairs. Length, 2 mtn. 



This species is much like nivicola, 

 but differs chiefly in having slender su- 

 perior claws, suboblong inferiors, long 

 anal spines, and clothing of another type. 



Orono, Maine, F. L. Harvey; Arling- 

 ton, Massachusetts, January 16, March 

 I, 10, 20, April 8, 9, 12 ; Annapolis, 

 Maryland, January 15, C. E. Munroe 

 (M. C.Z.). 



