NO. 18 



SENSE ORGANS OF COLEOPTERA — MclNDOO 



53 



and / on the legs (fig. 9) can be counted by inspection. Group 7, con- 

 sisting of 8 slit-shaped pores, lies on the ventral surface of the ter- 

 minal segment of the maxillary palpus. All the remaining pores 

 counted are isolated ones found on the antennae and mouth parts. 

 The total number of pores on all appendages of the same bean lieetlc 

 are as follows: Wings 397, elytra 136, legs 95, maxillae 32, labium 

 14, antennae 8, mandibles 6, and labrum 4, making 692 in all. The 



Fig. 15.— Internal structure of sense organs on adult Mexican bean beetle, 

 X 500. A, an olfactory pore, gland cell (GC), and sense hair from dorsal surface 

 of labrum. B to G, olfactory pores; B, from mandible, C, from maxilla; D, 

 from elytron; E, from trochanter; F, from tibia; and G, from wing. H, sense 

 hair from trochanter. I, drawing, two-thirds diagrammatic, from longitudinal 

 sections of distal end of labial palpus, showing innervation of so-called taste 

 hairs (THr), tactile hairs (St), and olfactory pore (P). J, semidiagrammatic 

 drawing from> 3 cross sections through base of first antennal segment, showing 

 tactile hairs (St), gland pore (Po), olfactory pore (P), trachea (Tr), and 

 nerve (N). 



fact that this number is small for an adult insect might be correlated 

 with the fact that the bean beetle is " stupid " when the olfactory re- 

 sponses are considered. 



The olfactory pores on several individuals of all four instars of 

 bean-beetle larvae were examined. Since no differences in number 

 and position were observed, the pores were carefully studied on only 

 individuals of the fourth instar. They are illustrated in figure 16. 

 The total number of pores on all appendages and the head are as 

 follows: Legs 30, maxillae 12, head capsule 6, antennae 4, labrtmi 4, 



