ASSEMBLING. 345 



said that, although the wings of the female are of fair size, 

 they are not nearly as firm as those of the male, and it 

 would seem that by disuse they have become weakened ; 

 and, if the present conditions are continued sufficiently long, 

 the wings of the female gypsy moth may suffer the same fate 

 as those of the female of the white-marked Tussock moth 

 (Plate 39, Fig. 18). 



The peculiar zigzag flight of the male may be the result 

 of natural selection. As the female does not fly, the male is 

 guided to her by the odor which she gives off, and which is 

 disseminated by currents of air ; and it is evident that males 

 flying in a straight line would not meet with the scent-laden 

 currents in as many cases as those which fly in a zigzag 

 course. It is therefore probable that more of those having 

 a tendency to an irregular course in flight would find and 

 mate with the females, and thus transmit to their male 

 offspring a like tendency to this particular flight, which, in 

 the course of generations, has become a fixed characteristic 

 of this species. 



THE ASSEMBLING OF THE GYPSY MOTH. 



It is a well-known fact that unfertilized females of the 

 gypsy moth are able to attract the males to them from a 

 greater or less distance. This is called assembling, and this 

 power to assemble is possessed by quite a large number of 

 moths more or less nearly related to the gypsy moth. 



As has been previously stated, the caterpillars of this 

 insect have the habit of spinning down, or suspending them- 

 selves from the trees on which they feed, especially when 

 disturbed ; and they frequently fall upon passing teams or 

 animals, and are carried by them to places more or less 

 remote. If, in any such case, caterpillars should be carried 

 into an uninfested region, and, making their way to suitable 

 food plants, should, in transforming, give rise to female 

 moths, there would be little or no danger of their establish- 

 ing a new colony, unless they should attract male moths 

 from the infested region, and, having mated with them, 

 should therefore lay fertile eggs. 



The following experiments were made by Mr. A. H. Kirk- 

 land, assisted by Mr. J. P. Hylan, for the purpose of deter- 



