OBSERVATIONS ON THE BIONOMICS OF STEGOMYIA FASCIATA. 209 



died, and in another experiment carried out by me a female continued to lay fertile 

 eggs up to the date of her death 37 days after the last possible date of fertilisation. 

 The details of this experiment are not included here, as they have already been pub- 

 lished in the Annual Report of the Laboratory, Accra, for the year 1914. 



The blood feed must follow fertilisation. It is not the same thing if the meal of 

 blood precedes fertilisation as is shown by experiment No. vii. In this experiment 

 a newly hatched and unfertilised female Stegomyia fasciata was isolated and allowed 

 to feed on blood. This she did on the third day. The next day two males were 

 introduced into the same jar, and fertilisation took place immediately. Nevertheless 

 no eggs had been laid up to the tenth day, when a second feed of blood was permitted, 

 although the subsequent history of the mosquito showed that under the conditions 

 provided she laid her eggs regidarly on the third day after each blood feed. 



In nature it probably happens occasionally that the female Slegcmyia fasciata fails 

 to procure a meal of blood immediately she is ready for it. The effect of such a delay 

 is exemplified in experiment No. vi. The mosquito in this case laid her first batch 

 of eggs on the sixth day of her adult life, on the third day after her first blood feed, 

 and her second batch on the ninth day at a similar interval after the second feed. 

 Her third batch of eggs was therefore due on the twelfth or tliirteenth day. But 

 instead of allowii]<:f her to feed on blood on the ninth day immediately after she had 

 laid her second batch of eggs, she was prevented from doing this until the eleventh 

 day. Her third batch of eggs was laid on the fifteenth day, that is two days late, 

 but on the fourth day after the last blood feed. The effect of delaying the blood 

 meal was therefore simply to delay the laying of the next batch of eggs a correspond- 

 ing number of days. In experiments Nos. iv. and v. the mosquitos were prevented 

 from feeding on blood for the first ten and seventeen days of their adult hves 

 respectively. The only noticeable effect of this deprivation was that the total 

 number of batches of eggs laid was reduced by the numbers that might have been 

 expected to have been laid during these periods of blood starvation. 



Temperature. 



It was thought that possibly the lowering of the temperature might have something 

 to do with the slight preference that seemed to be shown by the mosquitos for feeding 

 at night. Two experiments (Nos.ix. andx.) were therefore carried out to determine 

 the efi:ects of a high temperature on Stegomyia fasciata. 



In each of the experiments newly hatched mosquitos were isolated in glass jars 

 under the same conditions as in the other experiments, but the jars were kept in an 

 incubator at 37° C (98'6° F) excepting during two periods of about half an hour at 

 8-9 a.m. and 2-3 p.m. each day, when they were removed so as to give the mosquitos 

 an opportunity of feeding on blood. The mosquitos were incidentally in darkness 

 also for the greater part of each day. 



The high temperature did not obviously inconvenience the mosquitos ; both 

 males and females were active, drank honey readily, and paired frequently. Thoy 

 did not survive long, however; the five males lived only 4, 3, 8, 1, and 9 days 

 respectively, and the two females 18 and 11 days. In the case of the females other 

 effects were observed. The second female (experiment No. x) did not feed on blood 



