October, '21 1 freeborx: anopheles occidentalis 421 



An interesting feature in the study of t.hese collection data is to be found 

 in a comparison of the first season (1919) with the second season (1920). 

 During 1919 the nearest rice field was some distance away but during the 

 interv'ening \^-inter the entire area surrounding the bridge was leveled for 

 rice and the collections for 1920 therefore show the rate to be expected 

 from, rice fields in that particular vicinity. The writer does not care to 

 comjnent on this phase of the problem as Mr. W. C. Purdy of the U. S. 

 Public Health Service, who so kindh^ made the collections upon which 

 these studies are based, already has in preparation a report of this ]3hase 

 of the work which will undoubtedly be published at an early date by 

 his ser^dce. 



vSuMMARY 



1 . Efficient mosquito-m.alaria control depends on an intimate knowl- 

 edge of the life histon- of the m.osquito in question and can not be based 

 on the known life histon.- of another species. 



2. In California .4 . occidentalis D . & K. overwinters as an adult female, 

 hibernation beginning about November loth and terminating in Feb- 

 ruary' in a widespread migrators- flight. 



3. These over\vintering females evidently lay but few eggs and have 

 all disappeared by April at which time all the individuals of the species 

 exist as lan^al forms. 



4. The first brood of the year reaches its peak in June. The indi- 

 viduals of this brood have the ability to lay many series of eggs which 

 accounts for the accumulative peak pf mosquito population that occurs in 

 September. 



5. The species apparently passes thru two generations in a season with 

 the possibility of a third or fourth under the most favorable circumstan- 

 ces. 



6. Control work directed against the larvae after the spring migratory 

 flight of overwintering adults and again after the peak is reached in the 

 fall, if carefully done, will hold this species under control. 



Bibliography 



Herms. W. B. and Freeborn, S. B. — "The Egg Laying Habits of California .Ano- 

 phelines" Journal of Parasitology — Vol. VII — pp. 69-79. 



Knab, Frederick: — "The Swarming of Anopheles punctipennis Siiw" Psychi — Vol. 

 XIV— pp. 1-4. 



MiTZMAix, M. Brui.v: — "Is Mosquitoor Man the Winter Carrier of Ma lari i Organ- 

 isms?" Public Health Service — Bulletin No. 84 — December 1916. 



I 



