OBSERVATIONS ON THE BIONOMICS OF STEGOMYIA FASCIATA. 207 



which breeds in the immediate vicinity of human dwelUngs, to be unable to obtain a 

 feed of blood for more than a day or two at a time ; and it is improbable that she is 

 ever called upon in nature to subsist for long on honey alone, even if it is a fact that 

 she does sometimes naturally drink nectar. When blood is obtainable it would seem 

 that this is the chief food of the female mosquitos, although in the course of my 

 experiments it was sometimes noticed that they appeared to have fed on honey 

 between their blood feeds. 



In those experiments, for example Nos. i. and ii., in which an opportunity of feeding 

 on blood was afforded at least twice a day from the time of emergence from the pupal 

 state, the females fed for the first time on the second, or more often the third day, 

 and did not feed again until after the first batch of eggs had been laid. For the rest 

 of their lives they fed regularly once, but only once, soon after each batch of eggs 

 had been laid ; and as the eggs were generally laid every third or fourth day, the blood 

 feeds also took place every third or fourth day. There were of course slight irregu- 

 larities in the habits of the individual mosquitos, but a careful examination 

 of the details of the experiments that are given below will show that the above state- 

 ments are justified. An unfertilised female, however, behaved differently (see 

 experiment No. viii). In her case, although blood feeds were taken, they did not 

 occur at such regular intervals, and no eggs were laid. 



After it had once been ascertained by a large number of observations that the 

 mosquitos never fed on blood excepting just after a batch of eggs had been laid, it 

 was considered unnecessary to continue to ofTer the arm for feeding twice every day 

 unless some particular object were in view. Instead, as in experiment No. iii., the arm 

 was offered after each batch of eggs had been laid until the mosquito fed, and then 

 was not offered again until after the next batch had been laid. This simplification 

 could not, I think, have had any effect on the course of the experiments ; and in 

 any case it was not resorted to until after the general habits of the mosquitos had been 

 thoroughly studied in a number of experiments. 



A good deal of interest has been expressed in the hours during which Stegotnyia 

 fasciata feeds on blood, owing to the behef that yellow fever is transmitted at night 

 time only. In my experiments it was found that the mosquitos at all ages might 

 feed at any hour, the time depending on the time at which the eggs had been laid. 

 In the majority of cases the eggs were found in the early morning or in the evening, 

 and the mosquitos were generally ready to feed very soon after the last egg had been 

 deposited They would not, however, feed during the period when they were actually 

 depositing their eggs. Thus the mosquitos whose eggs had been found in the early 

 morning were ready to feed on blood at the first opportunity afforded during the 

 succeeding day, and those that had laid their eggs in the afternoon or evening fed the 

 same night. It did occur sometimes that a female that had laid her eggs early in the 

 morning refused to feed on blood until the following evening ; and on the whole in 

 the experiments it was found that a larger proportion of the opportunities of blood 

 feeding were taken advantage of at night than in the day. 



If the conditions of the experiments had not greatly modified the habits of the 

 mosquitos, we must conclude that the female Stegomyia fasciata in nature sets out 

 in search of blood as soon as she has finished laying each batch of eggs, and that she 

 is almost equally likely to bite by day or night. There was no evidence that, as has 



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