ANATOMY AND PHYSIOLOGY 



101 



insects ; thus there are as 

 many as 17,000 on each an- 

 tenna of a blow fly (Hicks). 

 The male of Melolontha vul- 

 garis, which seeks out the 

 female by the sense of smell, 

 has according to Hauser 39,- 

 ooo pits on each antenna, and 

 the female only 35,000. Pits 

 presumably olfactory in func- 

 tion have been found by 

 Packard on the maxillary and 

 labial palpi of Perla and on 

 the cerci of the cockroach 

 Periplaneta americana. Vom 

 Rath has described four kinds 

 of sense hairs from the two 



FIG. 134. 



Longitudinal section of a portion of a 

 caudal appendage of a cricket, Gryllus 

 domesticus. b, bladder-like hair; c, cutic- 

 ula; h, hypodermis; n, nerve; ns, non- 

 sensory setae; sc, sense cell; sh, sensory 

 hair. After VOM RATH. 



FIG. 135. 



sense ceils. After VOM RATH, 



larger of the four caudal appen- 

 dages of a cricket, Gryllus; some 

 of these (Fig. 134) may be olfac- 

 tory, though possibly tactile. The 

 same author found on the terminal 

 palpal segment in various Lepidop- 

 tera a large flask-shaped invagina- 

 tion (Fig. 135) into which pro- 

 ject numerous chitinous rods, each 

 a process of a sensory cell, which 

 is supplied by a branch of the prin- 

 cipal palpal nerve; these peculiar 

 organs are inferred to be olfactory. 

 The chief reason for regard- 

 ing these various end-organs as 

 olfactory is that they appear 

 from their structure to be better 

 adapted to receive that kind of 

 an impression than any other, so 



