874 



SCIENCE 



[N. S. Vol. XLI. iSTo. 1067 



porous clay plates (Y7 mm. — 3 in. — in diam- 

 eter) mounted across the large end of a glazed 

 porcelain funnel. The apparatus is made as 

 a single piece, the funnel wall and the disk 

 being continuous, and the lateral surface is 

 afterwards heavily glazed externally. The 

 funnel part is nearly hemispherical, with the 

 cylindrical neck projecting outward from the 

 spherical surface, opposite the center of the 

 porous disk which closes the hemisphere at the 

 top. A vertical section of such a piece is 

 shown in Fig. 1. In operation, the opening 



Fig. 1. 



is closed by a rubber stopper bearing a tube 

 reaching to the water reservoir below, just 

 as in the case of the ordinary porous cup 

 atmometer. Of course it is not at all essen- 

 tial that the plate be horizontal; it may be 

 exposed in any direction, even downward. All 

 that is necessary is that the water level in 

 the reservoir be at a lower level. It maj be 

 mounted on a bottle or a burette, or any con- 

 venient form of reservoir, and the non-absorb- 

 ing mounting may be employed to prevent the 

 absorption of rain. In general, these Bellani 

 plates are to be operated just as are the ordi- 

 nary porous cups. Where a plane evaporating 

 surface is required, they possess all the advan- 

 tages of the free water surface and none of its 

 disadvantages. They also possess all the gen- 

 eral advantages of the porous cup . instru- 



■^^'^ Burton E. Livingston 



the effect op temperature on the life cycle 

 of musca domestica and culex pipiens 

 Owing to a scarcity of data necessary to 

 illustrate the relation of the temperature to 

 the rate of breeding of flies and mosquitoes, a 

 set of experiments was undertaken at the sug- 



gestion of Professor C.-E. A. Winslow, to 

 determine (approximately) this relation. 



These experiments were made possible 

 through the courtesy of the department of 

 natural history of the College of the City of 

 New York in loaning us three incubators for 

 the purpose. 



The experiments began late in July, 1914, 

 and ran through to the middle of September. 



An effort was made to eliminate all factors 

 but that of temperature. 



Individual variations among different 

 batches of eggs were eliminated by dividing 

 the same batch into three portions to be incu- 

 bated at the three temperatures. 



Larvffl reared from the batches of eggs com- 

 pared were fed on the same food. 



The light, throughout, was either diffused 

 or absent, and the same condition obtained in 

 the batches compared with each other. 



By exposing several tumblers of water in 

 each incubator, the atmosphere was kept in a 

 high state of saturation. 



All vials containing the breeding fly larva 

 were of the same cross section and the height 

 of manure was about the same in each, i. e., 

 from 1^ to 2 inches; the mosquito-larvK vials 

 and infusions were also uniform. 



From the above it will be seen, that although 

 the results may not indicate a breeding rate 

 generally true for each temperature, they never- 

 theless offer a fair comparative study of the 

 rate at the three temperatures. 



Experiments with Flies 

 Experiments with the life cycle of flies will 

 be treated first. 



Egg batches were obtained in the following 

 way: Elies were caught by net and females 

 with gorged abdomens selected. These were 

 first placed together in large fruit jars con- 

 taining rotten fruit (plums), and the jar was 



TABLE I 



Average Duration of Each Stage — Flies 



