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MOSQUITOES OF NORTH AMERICA 



inches deep, shaded in the morning. Duckweed abounds here, and a quantity of 

 green algae cover the sticks and stone of the bottom; the pool swarms with 

 Culex and Anopheles punctipennis larvae; (d) Thirty-five feet above (c) is an 

 ' iron ' pool with a deposit of iron ; it is about 9 feet by 9 feet, 10 inches deep, 

 partly shaded by bushes and a huge log. It contains no vegetation and no larvae. 

 Of these four pools the smallest one, in the center of the row, is the only one con- 

 taining Anopheles larvas. These larvce are exclusively those of A. punctipennis, 

 while in the river only a few feet from here, A. maculipennis is abundant. 



" Another noticeable feature of the distribution is the entire absence of all 

 mosquito larvae from the bayou, although the water is currentless, the vegetation 

 abundant, and the light and shade favorable. It is probable that the duckweed 

 and lily pads cover the surface too closely in the shallow water near the shore. 

 As pool (c) above described became choked with duckweed later in the season, 

 the larvae disappeared. 



" The following table shows the undoubted selection of different breeding- 

 places by A. maculipennis and A. punctipennis : 



" The fact that the breeding-places are only a few feet apart renders especially 

 remarkable the specific preference displayed. The predominance of A. puncti- 

 pennis in the other two regions that were examined is in accord with the obser- 

 vations in Michigan. A. punctipennis shows a predilection for spring-fed pools, 

 and, in localities where these abound, is the chief species. Hirschberg and 

 Dohme observed a rather definite geographical distribution of the two species 

 in the vicinity of Baltimore, A. maculipennis being found on low ground in or 

 near large bodies of water, while A. punctipennis was found in small, clear 

 streams or springs on higher ground." 



Smith in New Jersey says of A. punctipennis, " On the whole it breeds most 

 abundantly in clean water along the edges of ponds or swamp areas or in the 

 eddies of shallow streams." Concerning A. quadrimaculatus, he says, "The 

 breeding places are similar, but this form also occurs in brackish water on the 

 salt marshes, hence has a somewhat wider range and adds the positive danger 

 of disease to the disadvantages of an undrained marsh." 



J. K. Thibault, Jr. (in litt.) states that at Little Rock, Arkansas, Anopheles 

 punctipennis is the most abundant species in the city and that it is scarce in the 

 country; but that A. quadrimaculatus is the more abundant mosquito in the 

 river-bottoms but is scarce in the city. 



An interesting point has been brought out by Button in his report of the 

 malaria expedition to the Gambia (Liverpool School of Tropical Medicine — 

 Memoir X), to the effect that the number of mosquito breeding-places present 

 in compounds was found to vary with the social position of the occupier, and in 

 this statement he includes Anopheles mosquitoes. The following is taken from 

 his report : 



