212 MOSQUITOES OF NORTH AMERICA 



which had fed well B|::|. The unfed males were more closely concordant than 

 the unfed females, the latter varying over about a semitone. Mr. J. W. Cap- 

 stick, M. A., Fellow of Trinity College, Cambridge, to whom we are greatly 

 indebted for making these ear determinations for us by means of tuning-forks, 

 was not certain that the note given by the males was not one of 440 vibrations. 

 Overtones were obviously strong and it sounded at times as if there were a faint 

 note of 440 vibrations overshadowed by a strong one of 880. 



" The obvious explanation of the higher note given off by the males is that 

 their wings are markedly narrower and shorter than those of the females. Al- 

 though a female Culex pipiens gave a higher pitched note than a female A. 

 maculipennis, we are not at all sure that it was not simply due to the smaller 

 size of the former insect. The male of this species of Culex certainly gave a 

 higher pitched note than the female." 



DISTANCE OF FUGHT. 



Distances to which malarial mosquitoes will fly is a very important point in 

 the consideration of malarial prophylaxis. It seems reasonably sure that they 

 are much less capable of extended flight than many other mosquitoes and that 

 ordinarily they travel but a very limited distance. Statements that Anopheles 

 fly a long distance may be set down as based upon faulty observations. Thus 

 Craig has recently stated that he determined a flight of Anopheles of two and a 

 half miles in the Philippines. The difiiculty of determining, in a tropical region, 

 that no breeding-places are present within a radius of two and one-half miles 

 must be obvious. When we consider that Anopheles larvae may exist in the 

 water-filled foot-prints of animals, and that these may be hidden by vegetation, 

 that furthermore they may breed in hollows in trees, or in water-bearing epi- 

 phytic plants, the task of determining with absolute certainty the absence of 

 breeding-places over a large area will be clearly seen to be impossible. Grassi 

 already pointed out that on account of the absence of scaly covering these mos- 

 quitoes are less able to withstand desiccation than others and that, therefore, 

 they can not cross large areas which afford them no shelter from the direct rays 

 of the sun, 



Pressat, who made careful studies at Ismai'lia in Egypt, objects to the state- 

 ment of certain authors that Anopheles fly very long distances and points out 

 that they are not capable of sustained flight. He affirms that, when Anopheles 

 are present, careful search will reveal breeding-places within a distance of a few 

 hundred yards. Pressat admits that under certain conditions Anopheles, pro- 

 gressing by stages, travel considerable distances. When they are found at great 

 distances from their breeding-grounds they have reached the place in a passive 

 manner, transported by wagon, by railway or by boat. They may travel with a 

 caravan, as he determined by actual observation at Ismailia, by resting upon the 

 animals, the baggage or clothing. Pressat believes that Anopheles can not cross 

 a region denuded of vegetation, or a considerable expanse of water. On the other 

 hand wooded country affords them the necessary shelter and the animals found 

 there furnish them food. 



Celli has concluded, from his observations in Italy, that Anopheles do not fly 

 farther than from 200 to 350 meters. When at greater distances from their 



