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OBSERVATIONS ON THE BIONOMICS OF STEGOMYIA FASCIATA. 



By J. W. Scott Macfie, M.A., D.Sc, 

 West African Medical Staff. 



The life-history and habits of Stegomyia fasciate have of course been most carefully 

 studied. On looking thi'ough the literature at my disposal, however, I was unable 

 to ascertain certain points with regard to the feeding and breeding of individuals that 

 I was anxious to know, and I therefore undertook some experiments myself to deter- 

 mine these. A few notes on my observations may perhaps be of interest to others, 

 and my excuse for recording them must be the importance of even the most trivial 

 details in the hfe of the insect responsible for the spread of yellow fever. The 

 experiments were all made under similar conditions, and as it was found possible to 

 rear many successive generations of Stegomyia fasciata under these conditions, it is 

 perhaps justifiable to suppose that the habits of the insects were not greatly affected. 

 It is impossible to make such observations under absolutely normal conditions, and 

 it may be doubted whether any closer approximation to the natural state that is 

 compatible with close observation would materially improve the results. It should 

 be stated clearly that the experiments relate only to Stegomyia fasciata. The habits 

 of other species of even the same genus, as for example those of Stegomyia metallica 

 with which I have had an opportunity of working, are notably different. 



Stegomyia fasciata is, fortunately for the experimenter, but unfortunately for the 

 sanitarian, exceedingly easy to breed. In the laboratory in any sort of jar or tin, 

 and in all sorts of fluids, the larvae received from the sanitary inspectors matured, 

 pupated, and hatched into adults ; and if feeds of blood were provided, no difficulty 

 was experienced in obtaining eggs and further generations of larvae. Not only did 

 |te mosquitos breed readily when kept together in large numbers, but single indi- 

 viduals and pairs did not appear to be affected in any way by isolation. This was 

 fortunate, as it was my object to study the habits of individuals, and this would have 

 been practically impossible had it been necessary to deal with large numbers of 

 mosquitos in each experiment. 



In each experiment a single female was isolated with, or sometimes without, one 

 or two males. Only recently hatched mosquitos were employed, that is, such as had 

 emerged from pupae on the same days as the experiments were started. The mos- 

 quitos were placed in a roomy glass jar, at the bottom of which there was a layer of 

 water, and over the mouth of which a piece of gauze was tied. An arch of folded 

 paper was fixed in the middle of the jar for the insects to rest on, and on the upper 

 surface of this drops of honey were laid. The jars were changed frequently, and 

 fresh honey was supplied almost daily. For the purposes of the experiments the 

 bared forearm was apphed at various hours of the day or night to the gauze coverings 

 of the jars, and allowed to rest there for ten minutes. This was found to be ample 

 time for the mosquitos to feed if they wished to do so. At the end of this time the 

 mosquitos were examined, those that had fed being readily identified by the bright 

 (C206) Wt.P8/91. 1.000. 11.15. B.&FLtd. Gp.11/1. a 



