258 THE MOSQUITOES OF NEW JERSEY 



As we have seen, the only enemy of the mosquito which is maintained 

 in sufficient numbers to penetrate large areas of recently overflowed 

 land and eat up an enormous number of mosquitoes before they can 

 emerge are the salt marsh minnows. In dealing with the same problems 

 in recently overflowed lands along the course of a river, although the 

 stream may be well charged with minnows, the area overflowed is usually 

 so large that the supply of minnows is totally inadequate to do the 

 job. The salt marsh minnows are apparently anxious to penetrate the 

 salt marsh everywhere while the tendency of the fresh water minnow is 

 to stay in the more open water. 



An idle dream in the New Jersey experience is the idea that a sump 

 hole in the midst of a temporary marsh in which predatory insects are 

 maintained will support a sufficient supply of them to eat up the bil- 

 lions of mosquito larvae that hatch. Thus, except on the salt marshes, 

 the work of natural enemies has to be supplemented by the use of larvi- 

 cides and other methods of control. 



ATTRACTION OF MOSQUITOES TO MAN 



It is a well known fact that mosquitoes are attracted to the human 

 and animal kind for purposes of sucking blood. The writer has fre- 

 quently observed at dusk, while sitting in a screened enclosure with little 

 or no wind blowing, that female mosquitoes (C. pipiens, A. vexans, and 

 M. perturbans) concentrate on the screen wire directly over the spot 

 where he or others were sitting and that no such concentrations appear 

 elsewhere on the screens. Thus it seems evident that the attractive ma- 

 terials are gaseous and emanate from the body. 



Rudolfs (19) undertook to find out what materials having the human 

 body as origin attracted mosquitoes. Under the heading of urine and 

 perspiration decomposition products he studied urine, urea, glycocoll, 

 cystine, phenylalanine, aspartic acid, asparagine, glutaminic acid, 

 alanine, trypsin, tyrosin, gliodin, ammonium hydroxide (strong), am- 

 monium hydroxide (1 to 200), ammonium hydroxide (one-half drop of 

 weak solution on a strip of paper), acetic acid two per cent (drop on 

 piece of paper), and sweat. Under the head of sebaceous secretions and 

 substances found in it, he studied sebaceous secretions (human), hand- 

 kerchief rubbed on cow's back while hundreds of mosquitoes were alight- 

 ing and biting, cholesterol, oleic acid (drop on paper), benzoic acid, 

 oleic acid and benzoic acid, oleic acid and cholesterol, and stearic acid. 

 Under blood and some constituents, he studied human blood (fresh), 

 cow blood (fresh), beef (fresh), beef (boiled), beef bouillon, blood 



