June, 1906] KNAB : GOELDl'S " Os MOSQUITOS NO PARA." 71 



the evolutions and biting of the Stegomyias. It appears likewise to be 

 quite indifferent to strong odors as in one case that from a floor satur- 

 ated withcreoline did not affect them. Strong mediums are necessary, 

 such as fumes of sulphur, chlorine or strong fumigation with pyrethrum. 



The question whether Stegomyia fas data bites at night is of impor- 

 tance in view of the often mentioned " diarios de Petropolis," that is, 

 the security from yellow fever enjoyed by those who spend the day in 

 the city of Rio de Janeiro but return to their homes in the nearby 

 mountains before nightfall. The author professes that he approached 

 this question with great scepticism. However now he is in possession 

 of quite a number of perfectly verified cases in each of which the 

 mosquito was taken "en flagrante" and identified by him. These 

 cases occurred both at Rio de Janeiro and at Para. Nearly all the 

 cases observed at Para occurred in nearly the same manner, between 

 the hours of eight and eleven at night while the author was writing by 

 an electric light, the window open. The mosquitoes that alighted 

 upon the hands and sucked blood were generally Tceniorhynchus fasci- 

 olatus or Panoplites titillans but now and then a female Stegomyia 

 presented itself. The bites personally observed at Rio de Janeiro oc- 

 curred during the same hours in a room of the library. The author 

 always noticed that during the day he was more persecuted by Stegomyia 

 in that room than elsewhere and he quickly discovered that the mould- 

 ings and the upper and under sides of the shelves were the chosen 

 hiding places of these mosquitoes. These cases, however, are not the 

 rule but exceptional ; perhaps one in a hundred bites at night and then 

 only with light, not in complete darkness. The weak light of the 

 night-lamp in a sleeping room is perhaps sufficient. These observa- 

 tions do not weaken the statement that Stegomyia fasciata is essentially 

 a diurnal mosquito. Now and then some female overpowered by hun- 

 ger prolongs its hunt into the night, above all when stimulated and 

 guided by the light in a room. That Stegomyia will readily accept 

 blood at night in captivity the writer considers an anomaly due to the 

 unnatural laboratory conditions. There is a popular saying that to get 

 rid of mosquitoes it is only necessary to put out the light. This ad- 

 vice, if it does not simply allude to the fact that the healthy organism, 

 tired from the day's occupation, falls asleep more readily in a dark 

 room, must refer to Stegomyia fasciata. In the case of Culex fatigans 

 and Anopheles the promised result will certainly not be realized. 



But there is still the possibility that perhaps the female Stegomyias 



