396 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1921. 



that earlier in the season laid her eggs on a nearby leaf (pi. 2, A). 

 Since the caterpillars themselves are most interesting creatures, it is 

 truly regrettable that their architecture does not possess greater 

 aesthetic merit. But, though we can not admire its art, let us study 



the worm. 



Each bag is the domicile of one large family, and much of the time 

 it presents scenes of great activity. Most of the inhabitants are 

 usually busy spinning and weaving, laying extra sheets of silk on 

 walls already substantial, constructing stays and partitions within, 

 or running out scaffolding to neighboring leaves and twigs which 

 will soon become the foundation for an extension to the web. At the 

 same time, many others are within feeding on the surfaces of the in- 

 closed leaves, preparing to take the places of the present workers 

 when they lay off for dinner. A few apparently lazy ones, however, 

 may be stretched out inside the tent asleep ; but these are really those 

 that have grown to the point where their skins have to be shed, and 

 this process must be preceded by a rest. The bag has to be enlarged 

 daily, for, unlike human families which bring their food into their 

 houses for consumption, the webworm families build their houses 

 around their food. Since families are large and appetites never 

 appeased for long, this arrangement entails almost constant remodel- 

 ing and enlargement of the dining room. As a consequence the house 

 ever lengthens and expands, taking in more and more fresh leaves in 

 one direction, while deserted chambers string out in the wake of the 

 moving family, containing the dead and dying remains of leaves and 

 a litter of refuse and molted skins. 



The moths of the fall webworms appear in the spring, which is to 

 say, they emerge at this season from the chrysalids in the winter 

 cocoons, as will be described later. The exact date of their emergence 

 depends on the season and the latitude. They come out sooner in 

 the South than in the North, and appear earlier anywhere in a warm 

 season than in a late one. But in general they are about in May, 

 when, after mating, the females proceed to lay their eggs, selecting 

 for this purpose a leaf on some tree that will be proper food for the 

 future caterpillars. Most species of caterpillars are very fastidious 

 in their taste and will feed only on certain kinds of plants. The 

 parents of such have to know these preferences of their progeny and 

 most of them are very particular to select the right variety of herb, 

 shrub, or tree on which to lay their eggs, so that the infant cater- 

 pillars will not have to travel far to find a first meal to their liking. 

 But, the webworm caterpillars having small choice in a large menu, 

 including nearly all deciduous shrubs and trees, the webworm 

 mothers have little to do beyond suiting their own convenience. 



