TWO INSECTS OF THE ORCHAED — SNODGEASS. 507 



her spinning, weaving figure-8 loops over and over the entire inner 

 surface of the cocoon till the meshes of the latter are closed and the 

 whole becomes opaque, while the worker within gradually disappears 

 from view. This task continues for several horn's and the result is 

 the snug inner pupal chamber already described (pi. 3, G, e). 

 Finally the valves (/) are put into the short section of the cocoon 

 and this end becomes the front of the final edifice, i. e., the end from 

 which the moth is destined to emerge. Therefore, the last act of 

 the caterpillar before molting is to arrange herself with her head 

 toward the valves, so that when the skin is cast off the pupa may lie 

 in position to break through the proper end when the time for the 

 emergence of the moth arrives. 



The caterpillar can not stretch out full length in the pupal com- 

 partment, because the latter is much shorter than the length of the 

 outer cocoon, which is scarcely longer than the length of the fully 

 extended caterpillar. But all is well with the shedding of the skin 

 for, by the accompanying change to the pupa, the creature shrinks 

 to half its larval length. The moth again (pi. 2, D) is still smaller 

 than the pupa and, except for its wings, looks entirely too diminu- 

 tive to be the parent of such a monster as a full-grown caterpillar 

 (pi. 2, /). The mature caterpillar, therefore, represents the period 

 of maximum bulk attained by the insect, after which there is a retro- 

 gression in size. This is accounted for by the fact that the cater- 

 pillar is a specialized feeding stage in the insect's life, during which 

 it manufactures within its body a sufficiency of food products to 

 carry it through the fasting pupal stage and to supply most of its 

 wants as a moth, whose special function is that of reproduction. 



There is nothing more delicately beautiful in insect architecture 

 than the freshly spun, waxy white, finely ribbed cocoon of Buccu- 

 latrix, surrounded by its bristling wall of delicate thread-like pali- 

 sades (pi. 3, H) . But exposure to the weather soon reduces this 

 fairy wigwam to a shabby thing of dirty gray, while the slender 

 palisades are so beaten down by wind and rain that by spring it 

 takes an expert search to locate even traces of them. At best a 

 stockade of silken hairs must be but a flimsy barrier against any 

 sort of enemy. And whatever military theory of defense the cater- 

 pillar may have held while building it, she evidently attaches little 

 of practical importance to it for, even as she erects the slender pick- 

 ets, she heedlessly brushes down those she has just set up and fre- 

 quently tramples others in her subsequent maneuvers. To the cater- 

 pillar, however, instinct says that a stockade must be there before 

 the cocoon shall be built, and the mandate of instinct is law in the 

 insect world. 



Many other papers have been published on these interesting little 

 pests of apple orchards, chief amongst which are those by J. H. 



