SIZE OF MESH 361 
Goeldi refers to this screen question, both in regard to the yellow-fever mos- 
quito and to the common rainwater-barrel mosquito, in connection with some 
very interesting observations about the range of variation in the size of the 
individuals of the same species, a fact which is frequently noticed with other 
insects but to which special attention has not been called elsewhere with 
mosquitoes. 
“Frequently I have observed, both in Stegomyia fasciata and in Culex fati- 
gans, alongside of individuals of normal stature, individuals very much smaller 
—veritable dwarfs. This observation may be made on specimens captured in 
freedom as well as on those in captivity, in this last case the phenomenon re- 
peating itself rather frequently. There are sometimes born individuals, both 
males and females, so small that they easily pass through the mesh of wire 
gauze much closer than the mesh of ‘ Grassi’s gauze’ which today is produced 
on a large scale in Italy with a view to the prophylaxis against Anopheles and 
malaria (Grassi, himself, recommends a gauze that shall not have less than nine 
meshes in 14 centimeters of distance, which corresponds to little linear squares 
1.7 mm. to theside). The government of the State of Para imported from Italy, 
for my experiments, a gauze under this name which had but six threads to 14 
centimeters of linear extension, corresponding to squares of 24 mm. along one 
side. I refer particularly to this last brand, which I consider sufficient as a rule, 
for application to hospitals, to impede the invasion of mosquitoes from outside, 
but which I found, nevertheless, insufficient for the walls of my cages destined 
for experiments on mosquitoes like Stegomyia fasciata and Culex fatigans in 
captivity. 
“Tn general, the phenomena of macrosomia and microsomia in plants and 
animals are related directly with greater or less abundant nutrition, and I do 
not believe that the quoted dwarf race of Stegomyia and Culex is to be explained 
in any other way than by a sparse alimentation and a delayed development in 
the larval stage. On this point I have at hand experiments in proof: Larve 
bred in clear water—that is to say, relatively poor in assimilable substances— 
gave me imagos of small stature. Furthermore, it is yet to be shown that I am 
deceived in my opinion that the frequency of dwarf individuals captured in 
freedom is not notably greater at certain periods, assuming almost the character 
of arule. Thus this year, in the last weeks of October and in November, before 
we entered fully upon the rainy season, I got the impression that the females 
of dwarf dimensions were particularly numerous. 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 argument that in 
the height of the dry season, with the growing lack of water, the conditions of 
life for the larvee become more difficult, thus favoring the generation of mos- 
quitoes 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 Culicide find its expression in two ways: (1) Delayed develop- 
ment of the larve; (2) Dwarfed stature of the imagos.” 
Note by Translator—Doctor Goeldi enters into a long explanation as to hiberna- 
tion, 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 
endeavors 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: 
