OLFACTORY ORGANS OF A COLEOPTEROUS LARVA 115 



the antennae, maxillary palpi and labial palpi. It is more 

 reasonable to regard these hairs as tactile organs and that, 

 in regard to aquatic larvae, food can be selected only by the in- 

 sects coming into actual contact with it, because water is perhaps 

 a poor medium for the distribution of odors. While feeding 

 mulberry leaves to silkworms, the present writer noticed that 

 these larvae perceived the food from a short distance and they 

 seem to 'know' when the leaves are in their presence even though 

 they can not see them nor touch them. 



THE OLFACTORY PORES 



Upon examining the integuments of the larvae of AUorhina 

 nitida, treated with caustic potash, many minute circular light 

 spots were seen on the head and on all of the appendages; these 

 spots resemble hair sockets from which the hairs have been re- 

 moved, but former studies dealing with similar spots on adult 

 insects suggested that these spots might be the olfactory pores, so 

 common to adult insects. On the last segments of the antennae, 

 several much larger light spots were also observed ; these resemble 

 the pore-plate sense organs, common to the antennae of certain 

 adult insects. Sections through the head and appendages show 

 that the, minute light spots are really the organs, called the ol- 

 factory pores by the writer, but instead of each large light spot 

 being a pore-plate sense organ, it is a group of olfactory sense 

 cells whose sense fibers pierce a thin place in the chitin, which 

 bears all the pore apertures belonging to that group of sense cells; 

 the thin place in the chitin may be called the plate. 



In order to distinguish the olfactory pores from the second type 

 of olfactory organ described above, the former may be called 

 single olfactory organs and the latter compound olfactory organs. 



1. Internal structure 



Before being able to decide definitely whether or not the 

 minute light spots on various parts of the integument are olfac- 

 tory pores or hair sockets, it was first necessary to study sections 

 through these spots. « 



