PROTECTION FROM BITES. 17 



frequency of dwarf individuals captured in freedom is not notably greater at certain 

 periods, assuming almost the character of a rule. Thus this year [1905], in the last 

 weeks of October and November, before we entered fully upon the rainy season, I 

 got the impression that the females of dwarf dimensions were particularly numer- 

 ous. I doubt that this is the work of a mere accident; it is very possible that 

 the frequency of dwarf individuals, normally possible during the whole year, may be 

 periodic and represent a case, somewhat diminished, of what is called in entomology 

 " dimorphism of seasons. ^^ Theoretically there can be no serious obstacle in accepting 

 the ai-gument that in the height of the dry season, with the growing lack of water, 

 the conditions of life for the larvae become more difficult, thus favoring the generation 

 of mosquitoes below the normal dimensions. Impoverished water and reduced food 

 may really, as we have seen above, oblige the larva to take two or three times the period 

 normally necessary for its development and to acquire the necessary growth for its 

 metamorphosis. I have the feeling that hibernation, in the sense in which this word 

 is accepted in zoologic literature, may well for the tropical and equatorial Culicidse 

 find its expression in two ways: (1) Delayed development of the larvae; (2) dwarfed 

 stature of the images. 



[Note by translator. — Doctor Goeldi enters into long explanation as to hibernation, 

 evidently for the benefit of equatorial readers who might accuse him of the mal-use 

 of technical terms. He refers to the phenomenon of "seasonal lethargy" and en- 

 deavors to trace a connection between the circumstances favoring the development 

 of the perfect insects in parallelism with the "periodicity of yellow fever." His 

 final paragraph is as follows:] 



It would be a mistake to believe that these dwarf individuals of Stegomyia are 

 less aggressive and sanguinary than those of normal stature. They behave in a pre- 

 cisely similar manner; their bites are not less painful, as I have had frequent occasion 

 to prove. 



A study of the question of mosquito bars or canopies, both for 

 indoors and out-of-doors, has been made by Dr. F. Arnold, the 

 district medical officer of health, northern Transvaal, and lie has 

 published an interesting article on the subject in the Transvaal 

 Agricultural Journal for October, 1907, pages 13-15. He illustrates 

 the mesh of different nettings purchased in Pretoria, labeling a netting 

 with a mesh 1 mm. in width as good, one of 2 mm. as doubtful, and 

 one of 3 mm. as bad. These nettings were tested by stretching 

 them over the mouths of three large pill boxes, and in each pill box 

 was put a known number of live, uninjured mosquitoes. The boxes 

 were placed on a chair alongside his bed, where they remained all 

 night, with the idea that by placing the mosquitoes near a sleeper 

 they would be anxious to get at him, and the natural conditions 

 existing in a bedroom would be imitated; that is, there would be a 

 mosquito and a sleeper separated by a net. The conclusions were 

 those above indicated. Doctor Arnold continues his directions in 

 the following words: 



In this country the bell-shaped bedroom mosquito net is almost always used; box- 

 shaped nets are rarely seen. In Eastern countries the box-shaped net is generally 

 used fixed on to a large four-posted bed; such an arrangement has the great advantage 

 that the net can be drawn tight and there is within it so large a space for the sleeper 

 that his limbs, if uncovered, are not likely to come in contact with the net, 

 37713— Bull. 88—10—2 



