i6o AGRICULTURAL EXPERIMENT STATION. 



There is always a great winter mortality and comparatively 

 a small proportion of specimens survive to reproduce. A gen- 

 eral cellar fumigation in districts were malaria is prevalent would 

 be of great benefit and would materially lessen the number O'f 

 the late summer broods. 



The life period during the summer has been incidentally dis- 

 cussed, and it is probably at least a month, under normal con- 

 ditions. So' the fact that a specimen may bite several times at 

 intervals has also' been referred to, and it is a necessity for the 

 transfer of malaria that the same individual should bite first a 

 person having the disease, and after a week's interval one who 

 does not have it but is susceptible. 



General Life History. 



So far as we know the life cycle of the species occurring in 

 New Jersey is identical, and the early stages are so much alike 

 that it is all but impossible to distinguish them. Dr. Dupree tells 

 me that he has found good characters in both eggs and larva; 

 but they are observable only with the compound microscope and 

 do not influence the habits in any essential way. 



The eggs are laid on the surface of the water, singly or loosely 

 grouped, so that they float on the sides in little masses among 

 the vegetation in which they are laid. From fifty to seventy- 

 five seems to- be an average for such a mass, thought there may 

 be either more or less. Sometimes, indeed, a larger mass is 

 broken into fragments and small groups of five or six, or even a 

 less number, are formed. The eggs are elliptical in shape, the 

 ends pointed, thoug'h not cjuite alike, and at first y'ltw the color 

 is black. Under the microscope they are seen to be quite pret- 

 tily marked and sculptured, the upper side being almost covered 

 by a clasping membrane which comes over from the side. The 

 length is about three one hundreths of an inch, or less than one 

 millimeter. 



The eggs hatch in about forty-eight hours, and the larvae 

 when they first become readily recognizable are black or black- 

 ish, marked with white or whitish spots and bands — "speckle- 

 backs," as Mr. Brakeley calls them. They vary greatly and no 

 two seem to be alike. Unlike the larva of Ciilcx, that of Ano- 

 pheles floats on the surface of the water and does not gO' beneath 

 it unless seriously disturbed. There is a very short anal breath- 

 ing tube and, altogether, the larva is quite different in appearance 

 from its ally. This habit of surface feeding enables it to live 

 in very shallow water, at the edges of pools and among masses 



