546 NEW YORK STATE MUSEUM 



when abundant it can be controlled in the same manner. This species is 

 one of the forms so well known as hop merchants, the hop being its 

 favorite food plant. 



Gray comma 



Polygon i a progtic Cram. 



A brown-headed, yellowish brown, spiny caterpillar about one inch in length, feeds 

 on elm. 



This species, according to Dr Fitch, is the more common spiny cater- 

 pillar found on elm. He states that it is white mottled with gray. It has 

 been described by Professor Fernald as follows : 



The mature larva is about one inch long, buff-colored, and armed with 

 branching spines as in P. comma Harr. Head subcordate, with a large, 

 compound, spinous process on each vertex, the main stem black, the branches 

 black and yellow, the face and sides of the head thickly covered with simple, 

 conical, yellowish spines of various sizes. The surface of the body varies 

 greatly in color and markings. 



The life history is very similar to the preceding and it can be controlled 



in the same manner. 



Four-lined sphinx 



CcratoDiia amyntor Hiibn. 



A stout, pale green or reddish brown larva about 3 inches long, with a conspicuou-s 

 caudal horn and four large tubercular elevations on the thoracic segments, occurs in early 

 September on elm, beech, linden and probably ash. 



This striking and to some disgusting larva is not uncommon in early 

 September, and on account of its peculiar appearance attracts more or less 

 notice, though it is rarely abundant enough to cause material injury to trees 

 on which it feeds. The recently hatched pale green larva emerges from a 

 spheric, greenish (t^^ and is then about '/s inch long. It has a straight, 

 brown-tipped caudal horn about half the length of the body and there are 

 four minute, tubercular processes on the posterior thoracic segments. 

 These latter structures continue throughout the difTerent stages and afford 

 a ready means of identifying the larva which, when full grown, ranges from 

 2^ to 3!/^ inches in length. It is then pale green or reddish brown with the 

 head and body strongly granulated. There is a dorsal row of fleshy teeth. 



