SONir ACTION OF ANOPHELES 211 



species in full sunlight, early in the spring, in Massachusetts. Smith states that 

 Anopheles crucians bites readily from sunrise until 11 a. m., and from 3 p. m. 

 until after dark. In his opinion it will bite any time during the day, provided 

 the victim is in a cool and sheltered location. Captain Fernside, I. M. S., ac- 

 cording to Giles, has seen an Indian Anopheles (presumably undetermined) 

 " feed greedily in the daytime," and a number of similar observations might be 

 quoted. 



Rev. James Aiken, in his " Notes on the Mosquitoes of British Guiana " (5th 

 Series), in the British Guiana Medical Annual for 1908, shows that at least one 

 species of Anopheles bites during the day in British Guiana. His statement 

 is as follows : 



" Anopheles during the day never by any chance attack in front, but in- 

 variably settle on some part of the anatomy invisible to the eyes of the subject 

 to be bled. I have often experimented with a hungry albipes, turning round 

 and following her with my eye as she vainly endeavored to lodge on the back of 

 my neck. As I am still somewhat sensitive I have sometimes occasion when 

 seated on a cane chair to rise and interpose a sheet of newspaper or some such 

 protection from the subtle attack of this troublesome gnat." 



THE NOTE OF ANOPHELES. 



The senior author pointed out in 1900 that there is a distinct difference be- 

 tween the buzzing sound or hum of Anopheles quadrimaculatus and that of Culex 

 pipiens, in that the former is indisputably lower in tone. His attention was 

 called to this by Mr. F. C. Pratt, who believed that he could at once distinguish 

 the two insects from the pitch of the hum as he was sitting reading in his house 

 in Virginia. The note of Culex, as it approaches the ear, is higher in pitch and 

 that of Anopheles is certainly several tones lower and not so clear. Tliis differ- 

 ence becomes at once perceptible by confining the respective insects under gauze 

 in a breeding- jar. 



Some interesting experiments on the sounds produced by Anopheles were 

 made by Nuttall and Shipley, who found that by cutting off more and more of 

 the wing the sound decreases in volume, the pitch rising progressively. 



" When the wing was cut off quite closely, a very high-pitched note of slight 

 intensity remained, this as we supposed being produced by an internal apparatus 

 such as Howard indicates. It may however be due to respiratory movements 

 which are exaggerated through the efforts at flight, the sound is not produced by 

 the insect in repose. We found that the males gave a higher-pitched note than 

 the females, and that the note was higher in both sexes when they had fed ; the 

 greater the meal, the higher the note. Of four unfed females three gave notes 

 within a quarter of a tone of 264 (t. e., of 240 to 270 vibrations), the fourth 

 female gave an abnormally low note of about 175 vibrations. Four other females 

 were arranged in the order of the distension of the abdomen by food, the last 

 being largely distended, these gave notes corresponding roughly to 264 — 281 — 

 297 — 317 vibrations or according to the musical scales, the notes : 



i 



^ 



i 



-i^©- 



" Three unfed males gave exactly the same note, viz. corresponding to 880 



vibrations \ fi~^ \ immediately after feeding one gave the note A ^, another 



15 



