126 N, E. McINDOO 



the pores observed on the ventral side of the head proper he 

 near the bases of the antennae and mandibles (fig. 28), while on 

 the dorsal side they are widely distributed from the labrum to the 

 occipital foramen. For a summary of the disposition of the 

 olfactory pores, see Table 1, page 130. 



b. Compound olfactory organs. The compound olfactory organs 

 are found only on the distal or last segments of the antennae. 

 Generally speaking, they lie equally on the dorsal and ventral 

 surfaces, although occasionally most of those present on an 

 antenna lie on one or the other of these surfaces, as shown on the 

 right antenna in figures 28 and 29. Sometimes two or three of 

 the smallest organs lie at the extreme end of an antenna, in such 

 a position that the plates may be seen, but the number of pores 

 in them cannot be accurately counted, therefore they must be 

 estimated. The plates invariably lie on the distal halves of the 

 segments and never on the proximal halves. 



Concerning the three specimens examined, the number of 

 plates observed on an antenna varies from 9 to 16, with 12 as an 

 average. The larger the plate, the greater the number of pores 

 it contains (figs. 23 and 24). The number of pore; in a plate 

 varies from 6 to 68, with 26 as an average. On both antennae 

 of specunen No. 1 (figs. 28 and 29) there are 27 plates, bearing 

 532 pores; of specimen No. 2, 19 plates, bearing 655 pores; and of 

 specimen No. 3, 28 plates, bearing 687 pores. It is thus seen that 

 on an average one of these larvae has 25 plates, bearing 625 pores. 

 Since these pores are practically .the same size as those in the single 

 olfactory organs, their total number may be added to that of the 

 single organs in order to compare the total number of olfactory 

 organs in a larva with that in an adult of the same species. 

 The writer (1915) has recorded 1,135 olfactory pores on the legs, 

 elytra and wings of an adult Cotinis nitida, and a reference to the 

 following table shows that the total number of olfactory pores in 

 a larva of the same species varies from 1,254 to 1,413, with 1,359 as 

 an average. Had the head and mouth parts of the adult beetle been 

 examined, the total number of pores found might have equalled 

 that found in a larva ; therefore, on the basis of the total number 

 of pores we may assume that the olfactory senses of the adult and 



