Nettling Insects 



SI 



through the cuticula for each individual hair, there is a single pore 

 for each papillae on a tubercle, all the hairs of the papilla being 



connected with the 

 underlying cells 

 through the same 

 pore canal, (figs. 

 39 and 40). 



The h3rpodermis 

 of this region is of 

 two distinct types 

 of cells. First, 

 there is a group of 

 slender fusiform 

 ceUs, one for each 

 poison hair on the 

 papilla, which are 

 the trichogen, or 

 hair-formative cells. They are crowded to one side and towards 

 the basement membrane by a series of much larger, and more promi- 

 nent cells (fig. 40), of which there is a single one for each papilla. 

 These larger cells have a granular protoplasm with large nuclei and 

 are obviously actively secreting. They are so characteristic in 

 appearance as to leave no question but that they are the true 

 poison glands. 



Poisonous larvae of many other species have been reported from 

 Europe and especially from the tropics but the above-mentioned 

 species are the more important of those occurring in the United States 

 and wiU serve as types. It should be noted in this connection that 



C FK 



38. Cross section of tlie larva of thebrowntail moth showing the 

 tubercles bearing the poison hairs. Drawing by Miss 

 Kephart. 



39. Epithelium underlying poison hairs of the larva of the 

 browntail moth. Drawing by Miss Kephart. 



