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The Identification of Certain West African Mosquitoes by Sound¹

1. All mosquito sounds are composed of a well-defined fundamental in the center of the audio range together with overtones, even in the case of sounds that sound like clicks. In some spectrograms as many as 15 distinctive frequency bands are recognizable.

2. All mosquito sounds have vibrato effects. Some species show tones with a single warble rate; others show double warble modulation. A common rate for the low frequency warble is from 2 to 15 cycles per second; the higher rate, when present, is often 5 times the lower. The magnitude of the lower rate may be some 5 to 10 per cent; the higher rate is about one-fifth to one-tenth the lower.

3. Male sounds are usually more broken than the female. In most cases the apparent pitch of the male is higher than the female of the same species despite but a small difference in their fundamentals. Mosquito sounds show a change of pitch with time; some increasing as much as 25 per cent in as little as 0.05 sec.

4. The intensity is modulated in all sounds. In some cases modulation is a complete interruption of an entire band or bands; in other cases, harmonics are varied only, leaving the remainder unaffected.

The spectrograms shown above are presented for the purpose of indicating some of the possible applications of modern electronic methods and apparatus in the study of the sounds of disease-carrying mosquitoes. They were made available to us through the courtesy of Dr. Oliver E. Buckley, President of the Bell Telephone Laboratories Inc. to whom we owe a debt of thanks not only for providing them, but also for his most welcome encouragement in our application of modern electronic apparatus to our study. It is the authors' considered opinion that the intensive application of such apparatus will make possible the precise, rapid, and simple observation of natural phenomena related to the sounds of disease-carrying mosquitoes and should lead to the more effective control of such mosquitoes and of the diseases that they transmit.

¹ Aided by a grant from the Tropical Disease Study Section, U. S. Public Health Service. The assistance of Morton C. Kahn, Jr. is gratefully acknowledged.

² Department of Public Health and Preventive Medicine, Cornell University Medical College, New York.