NYMPIIALINAE : POLYGONIA COMMA. 339 



appearing to be the favorite. Packard gives also currant, and French 

 bassvvood (Tilia) as food plants, plants in no way related to these, but 

 probably by error. Ambrosia has also been published as a food plant, 

 but in this instance Boehmeria had been mistaken for it. 



The larva is sometimes destructive to hop vines, so much so that they 

 have received a soubriquet in the farming districts, of which we have made 

 use. "These chrysalids," says Smith, in a report to government (Ent. 

 bull. Dep. Agric, iv : 40) " are known to growers and those engaged in 

 hop-yards as ' hop-merchants,' and according as the color of the metallic 

 spots [on the back] is golden or silver, so will the price of hops range 

 high or low, so the story goes." It is also applied to P. interrogationis. 



Habits of the caterpillar. Although the egg at the summit of a 

 column is the last of the series to be laid, it hatches first and the rest 

 generally follow in succession, there being a difference of many hours ; 

 all the caterpillars emerge on the same side of the column, and as 

 they escape from the crown of the egg, the column when emptied (for 

 they do not eat more than is necessary to escape) has a gentle curve, 

 tipped slightly in one direction by the escaping caterpillar. Immediately 

 it is out of the egg, the caterpillar is long enough to coil twice around the 

 interior of the egg, yet was coiled but once ! Sometimes, after eating a 

 hole large enough to escape from the egg, the caterpillar will rest motionless 

 for a couple of hours. The great point is to get the head out ; that done, 

 the rest glides smoothly enough, toppling the column overhead. I Avatched 

 once the last one of a column make his entrance into the world ; first he 

 took a grand tour of his old home, spinning a thread (as they always do 

 when young) all the way ; then he walked to the top of the leaning, tot- 

 tering tower, peered over into the empty crater of the egg at the summit, 

 shuddered visibly, and turned cautiously on his course, now with winding 

 and then with direct steps, until he reached the lowest egg, when he stretched 

 himself to the utmost and fastened a thread to the leaf beyond, to which he 

 then travelled. An hour was consumed in this performance. In early life 

 the caterpillars eat little roundish holes in the middle of one side of the leaf, 

 about 1.5 mm. in mean diameter, and when their meal is over rest with 

 their tails close to the hole, their heads toward the midrib. 



Although a number are usually born on the same leaf and several in 

 one cluster, and, therefore, for at least a part of its life, it does not lack com- 

 panions, this caterpillar is in no way social, but strictly solitary from birth on. 

 In early life it lives without concealment, but on the under surface of the 

 leaf. Later it may be found ' ' concealing itself on the under side of a 

 leaf, the outer edges of which are drawn together by silken threads suflEi- 

 ciently to afford a protection from light and the weather ; from this cover 

 the larva emerges at night to feed, and beginning at the extremity of a 

 leaf consumes it evenly across until not enough is left for shelter, when it 



