THE OLFACTORY SENSE OF COLEOPTERA. 4II 



species used for individual and sexual variations, only one speci- 

 men of each species was studied. Whenever a portion of an 

 appendage or an entire appendage was missing or was badly 

 mutilated in being prepared for study, the number of pores on 

 this portion or entire appendage was regarded the same as the 

 number found on the corresponding portion or entire appendage 

 on the opposite side of the bod}^ Since the pores on only one 

 specimen for each species were counted, the total number of 

 pores recorded can not be a fair average. Besides this error, 

 there is also a probable error of not less than 10 per cent, on an 

 average for all the specimens. In the smaller specimens the 

 probable error is perhaps not more than two or three per cent., 

 but in some of the larger ones, this error is probably more than 

 10 per cent. The pores on only the legs, elytra and wings are 

 included in the total numbers. Other parts of the insects were 

 not examined, and it is quite possible that olfactory pores may 

 be found on some of the parts not examined, particularly on the 

 mouth parts. 



(a) Epilachna borealis. 



Since the lady beetle, Epilachna borealis, is most conveniently 

 studied and as its pores are typical for most of the smaller beetles, 

 the disposition of its pores will be described in detail, and then 

 the variations found in the other species will be given. 



The elytra and wings have dorsal and ventral surfaces, and the 

 legs may be divided for description into two surfaces. The inner 

 surface faces the body of the beetle and the outer surface is 

 directed from the body. On the specimen examined, one group 

 of pores was found on the peduncle of each elytron ; three groups 

 besides a few scattered pores on each wing; and two groups 

 besides a few scattered pores on each leg. The groups and 

 scattered pores are located as follows: Group No. i lies on the 

 dorsal surface of the peduncle of the elytron with its distal or 

 broader end against or just beneath the basal margin of the 

 elytron (Text-fig. lA, BM). Under a high-power lens, it is seen 

 that this group lies on the radial plate (Text-fig. iB, RP) between 

 the muscle disk {MD) and the subcostal head {ScH). The distal 

 ends of these heavy chitinous plates sometimes lie beneath the 



