COTTONWOOD CATERPILLARS. 



433 



c. Variations in the markings of the elytra . 



1. Marked with black as follows: The suture ; two, more or less, oval spots near 



the base, the iuuer of which is nearer to the suture than to the lateral margin, 

 and the outer on the humerus; three longitudinal striiB on the middle, the in- 

 termediate of which is the longest; submarginal curved stria and an oval spot 

 between the latter and the suture. (Common at the West.) 



2. Additional marks: A small triangular basal spot in front and between the two 



subbasal markings. (Illinois.) 



a. This triangular spot is sometimes connected with the humeral spot. (Cali- 

 fornia.) 



/y. Black markings become wider or longer and then often confluent. 



y. Markings in general becoming smaller, either all of them, or one or several of 

 them. (C. V. Riley, Ag. Rep. for 1^84.) 



11. The COTTONWOOD DAGGER MOTH. 



Acrovycta populi Riley. 



Devouring the foliage and not unfrequently stripping the tree, a caterpillar which 

 rests curled around on the leaf, and is easily recognized by its body being covered 



Fig. 159.— The cottonwood dagger-moth and its caterpillar.— After Kiley. 



with long, soft, bright-yellow hairs, and a long pencil of black hairs on top of seg- 

 ments 4, 6, 7, 8, and 11. (Riley.) 



This caterpillar is sometimes destructive to the foliage of the cotton- 

 wood iu Missouri. There are two broods of these worms each year; the 

 first brood appearing in June and producing moths by the last of July, 

 the second brood appearing the last of August and throughout Sep- 

 tember, and passing the winter in the chrysalis state. It is attacked 

 by several parasites, i. e., a Microgaster, an Ophion, and a Tachina fly. 

 When fully grown the caterpillar spins a pale yellow cocoon of silk in- 

 terwoven with its own hairs, then turning to a chrysalis. It more com- 

 monly occurs on the balm of Gilead and Populus grandidentata. 



Pupa. — Is dark shiny brown, and ends in an obtuse point furnished with several 

 forked bristles. It lies within a pale-yellow cocoon of silk interwoven with tht' hairs 

 of the caterpillar and which is generally spun in some sheltered place, as in a chink 

 in the bark of a tree, etc. 



5 ENT 28 



