OBSRRVATIONvS ON THE BIONOMICS OF STEGOMYIA FASCIATA. 223 



Inbreeding of Stegomyia fasciata. 



On 4th March 1915 a number of mosquito larvae were obtained from a hollow 

 in a tree, the majority of which proved to be Stegomyia metalUca. As this species 

 had not previously been found n Accra, and as it was apparently one of the rarer 

 species in West Africa, I was anxious to obtain a large number of specimens, and 

 determined to attempt to breed the mosquito in the laboratory. Some doubt was 

 felt about he success likely to attend ihe experiment, for it seemed probable that 

 all ihe larvae or'g'nally obtained had been hatched from eggs laid by the same 

 mo' her, and they m'ght therefore have proved to be infertile, or but slightly 

 fer'i lie, when bred together. As a matter of fact, the adult Stegomyia metallica 

 mosquitos when isolated in pairs in glass jars did not breed, or did so only occasionally ; 

 but wh^n kept together in larger numbers they bred freely. The strain is still in 

 existence, and even now, after five months of inbreeding, appears to be as fertile 

 as ever. 



The ques^ ion as to whether mosquitos hatched from the same batch of eggs would 

 be fertile when bred together was not, however, answered by this experience with 

 S. metallica, as it was not known how many females had laid eggs in the hollow in 

 the tree in which the larvae were found. But as individual pairs of S. metallica 

 bred with such reluctance when isolated, experiments on these lines could not be 

 carried out with this species. S. fasciata on the other hand is very readily bred in 

 captivity, and it s habits do not seem to be affected by isolation. The two following 

 experiments were therefore carried out to determine whether males and females 

 of th's species ihat had hatched out from eggs laid in the same batch by the same 

 mother mosq 'ito were capable of breeding together and produc ng fertile eggs. 



Experiment XL A male and a female S. fasciata were isolated in a glass jar 

 containing a little water. The female laid a batch of eggs on 3rd May, and these 

 were isolated. On 6th May the first larvae hatched from these e^ggs ; on 

 13 h May the first pupae were seen ; and on 14th May the first adults emerged. 

 The aduhs were left together in the jar, and on 30lh May the first batch of 

 eggs was laid by them. 



Experiment XII. A male and a female S. fasciata were isolated in a glass jar 

 as in Experiment I. The female laid a batch of eggs on 24th May, and these 

 were isolated at once. On 27th May the first larvae hatched from these eggs ; 

 on 3rd June the first pupae were seen ; and on 5th June the first adults emerged. 

 The adul s were removed, and a single male and female isolated. This female 

 laid her first batch of eggs on 14th June. The eggs were isolated, and on 

 16th June the first larvae were seen to have hatched from them. These larvae 

 eventually pupated and hatched out into adult mosquitos. 



From these two experiments it is clear that adult S. fasciata mosquitos hatched 

 .from eggs laid by the same mother in the same batch are fertile with one another. 



In the case of S. fasciata the fact that inbreeding does not destroy fertihty can 

 have but little importance, since the species is so exceedingly common in Accra 

 that there can be no difficulty in the way of meetings between males and females 

 (C205) B2 



