THE VICTORIAN NATURALIST. 



growth varies at different seasons, being most rapid during the 

 spring and summer, when the grubs feed vigorously. During 

 the winter months, and particularly when located on deciduous 

 trees, young larvse in cases from one to three inches long may be 

 found with every indication of their having ceased feeding when 

 the tree shed its leaves. Many of these are dead, but some are 

 alive, and these begin to move about again in September and 

 October. From this time their growth is rapid, as a result of the 

 great quantities of food taken after their long fast. During the 

 winter also, and even as late as October, mature larvje in full- 

 sized cases, often much weather-beaten, may be found. These 

 have made no preparation for pupation, nor do they seem at all 

 inclined to eat. Most probably they have remained spun up at 

 least since the preceding May, and possibly for a whole year 

 before that. 



For the preservation of a species it is important that the 

 individuals are distributed over a considerable area, and in most 

 instances the mature insect effects this distribution by laying its 

 eggs, either singly or in small batches, in many different places. 

 However, the female Psychidye are devoid of means of locomotion; 

 they live always within a fixed abode. Any distribution must, 

 therefore, be effected by the larvse, and they have become pecu- 

 liarly adapted to lead a wandering life. They are able to exist on 

 almost any kind of plant, and can live without any food at all for a 

 considerable time. Their cases afford them protection from the 

 weather, and also from many birds and parasites, and the grub 

 itself is very hardy and peculiarly resourceful in emergencies, even 

 going so far as to construct a very neat little ladder for itself on 

 any surface so smooth that it would otherwise be unable to cling to 

 it — as, for instance, a sheet of glass. The rungs of this ladder are 

 about a quarter of an inch long, and are placed about the same 

 distance apart in a nearly straight line, each consisting of a fevf 

 threads fixed at the ends to the glass. There is a single thread 

 diagonally from one end of each rung to the opposite end of the 

 next higher, showing that the whole ladder is really formed of a 

 continuous thread. When the grub wishes to descend a difficult 

 place it may either withdraw quickly into its case and fall, or it 

 may, and if small usually does, let itself down at the end of a 

 thread, after the fashion of many spiders. The wandering nature 

 of this insect renders it difficult to follow up its life-history, and 

 these notes are compiled more from disconnected diary entries 

 than following through the complete life of any one specimen. 



A feature at once distinguishing these larvse from almost all 

 others is their habit of living within a movable domicile, 

 generally referred to as a case (fig. i), and it may be worth 

 while to allude briefly to its construction. 



As soon as the young larvae hatch they begin to build their 



