THE TRIBE OF THE CRESCENT-SPOTS 149 



How is it that the instinct to become lethargic Hes dor- 

 mant in the summer broods of caterpillars and shows itself 

 only in the autumn brood? Is it perhaps due to a reac- 

 tion to the colder nights of the later season? If so, possi- 

 bly one could get interesting light upon the subject by 

 experimenting with placing the summer caterpillars tem- 

 porarily in an ice chest. 



Synopsis of the Crescent-spots 



Baltimore Checker-spot (Euphydryas phaeton or Melitaea 

 phaeton). Expanse If inches. General color purplish 

 black with the upper surface marked thus: a marginal 

 row of red-brown spots between the veins; two rows of 

 creamy yellow spots inside of the row just mentioned; two 

 or three small red and two or three small white spots near 

 front border of each front wing. Under surface checkered 

 in red-brown and creamy yellow on a blackish back- 

 ground. 



Harris's Checker-spot {Cinclidia harrisii or Melitaea 

 harrisii). Expanse If inches. This species bears a close 

 general resemblance to the Silver Crescent. It may be 

 distinguished by the fact that the middle joint of each 

 palpus is of uniform size from end to end instead of taper- 

 ing toward its outer end. The tibial joint of the first pair 

 of legs of the male butterfly is very thick. The upper 

 wing surface is so marked with black that the tawny red 

 coloring shows only in the middle. 



Silver Crescent {Charidryas nycteis, Melitaea nycieis or 

 Phyciodes nycteis). Expanse If inches. This species may 

 be known from Harris's Checker-spot by the fact that the 

 middle joint of each palpus tapers from the middle to the 

 tip and that the tibia of each front leg in the male is slen- 



