54 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I39 



While it is probable that the organ of Johnston in the antenna of 

 most insects registers the movements of the flagellum, the elaborate 

 experimental work of Roth (1948) leaves no doubt that the highly 

 developed organ in the male mosquito is responsive to the effect of 

 sound waves on the flagellum. This, of course, does not imply that 

 the mosquito has an auditory "sense" ; mechanical reaction to stimuli 

 is all that we can attribute to the insects. Male mosquitoes are at- 

 tracted to the females in flight by the tone produced by their wings. 

 Roth showed that males with intact antennae, when subjected to the 

 sound of a tuning fork at 480 vibrations a second held behind a 

 suspended piece of cloth, fly to the source of the sound where they 

 exhibit typical mating activities though no females are present. Even 

 after complete removal of the flagellar hairs, males still respond to 

 more intense sounds apparently by vibrations of the shaft alone, but on 

 complete removal of the flagella they give no reaction. Roth's tests 

 were made particularly on Aedes, but males of other genera were 

 found to react similarly. Females of Aedes aegypti gave no evidence 

 of being attracted to sounds, "though they may give shock-reaction 

 to certain intensities." 



Further experimental work of Roth (1951) on females of Aedes 

 seems to show that the antennae function as directional distance 

 thermoreceptors and probably also as chemoreceptors. Females de- 

 prived of their antennae are unable to locate a host from a distance. 

 The antennae and the palpi are said to be the chief organs responding 

 to stimuli that induce probing by the proboscis. The receptor organs 

 of the antennae, however, are not described, but along the shaft of 

 the female antennae (fig. 22 B) are numerous hairs, and on the male 

 antenna (C) a ring of very short hairs encircles the distal end of each 

 flagellar section. The antennae of insects in general are known to be 

 the principal seat of chemoreception. 



The compound eyes of the mosquito are so large that they almost 

 encircle the head. Sato (1950, 1953a, 1953b) reports that by actual 

 count there are from 440 to 462 facets in the eye of a male Culex 

 pipiens, and 503 to 566 in the female ; and that in Aedes japonicus the 

 male eye contains 440 to 462 facets, the female eye 504 to 527. The 

 surface area of the eye in each genus is larger in the female than in 

 the male. The internal structure of the compound eye in Culex is 

 described by Constantineanu (1930) and by Sato (1950). 



An extensive experimental study of the visual responses of flying 

 mosquitoes made by Kennedy (1939) on unfed females of Aedes 

 aegypti shows that the mosquitoes react negatively to light, and are 



