370 R. W. GLASER AND J. W. CHAPMAN. 



worm seeks the tip of a grass blade and succumbs thereon. An 

 innate desire to reach an elevated place on their favorite food 

 plant always seizes the diseased insects prior to death. We 

 have never observed animals in the last stages of wilt descend 

 their food plants. So far we are unable to offer any explanation 

 which would satisfactorily assist in analyzing this ascending 

 instinct. A short time after death, the animals become deliques- 

 cent. At the slightest touch the skin ruptures and a dark brown 

 liquid oozes out. In some species such as the American and 

 forest tent caterpillars this liquid is pink shortly after death and 

 becomes dark brown later. The corpses will be practically 

 odorless if they have hung but a short time and before septic 

 bacteria have gained a foothold. 



If some of the brown liquid from a dead caterpillar is examined 

 microscopically with a high-power dry or oil-immersion lens, it 

 will be found to contain, besides the elements of disorganized 

 tissues, myriads of polyhedral bodies of various sizes. (Fig. I, 

 Plate i .) Certain polyhedra have been found to measure ^ M 

 and less in diameter while still others reach the size of 15 M- 

 The average polyhedron of the gipsy moth caterpillar measures 

 3.4 fj. in diameter. The bodies in this species are larger than 

 those in any other form we have hitherto examined. The average 

 size of nun moth caterpillar polyhedra measure 2.65 /JL in diameter; 

 those of the forest tent caterpillar 2.6 p and so on until we come 

 to Phyrganidia californica and the tussock moth caterpillars in 

 which the average diameter has been found to be 1 .6 /* and 1 .5 /* 

 respectively. Thus it is seen that the average polyhedron varies 

 greatly in size in the different species. As stated previously the 

 sizes of the polyhedra within one species or even within one 

 animal (gipsy moth: ^M~I5M) varies also. There exists a 

 striking similarity between the shapes of these bodies in the 

 different species but some variation within a particular species 

 or even within the same animal can be observed. In general 

 the form is that of a polyhedron with more or less rounded angles. 

 They never assume the shape of a perfect sphere, and an actual 

 geometric outline has never been observed except in the silk 

 worms where almost perfect octahedra are found. The poly- 

 hedra are highly refractive, and on focusing are seen to have a 



