1916 J ECONOMIC ZOOLOGY ENTOMOLOGY. 53 



temperature. It is pointed out that there is an absolute minimum fatal tem- 

 perature below which, even for the shortest time, life is impossible and that 

 there is also a corresponding absolute maximum fatal temperature; and that 

 absolute dryness is more or less prohibitive of life, as is absolute humidity, 

 i. e., saturation. 



In working out the relation of temperature and humidity the diagrammatic 

 figure sought has four definite absolute boundaries — the maximum and mini- 

 mum temperatures and humidities. " Within the limits which we have thus 

 defined there exist conditions under which all the activities of the species reach 

 their maximum efficiency. It has been conceived by most writers that this 

 maximum efficiency was reached at a definite point known as the optimum. It 

 seems more likely that it will prove to be a zone of humidities and tempera- 

 tures of more or less restricted area. A careful study of the records of any 

 species, charting for the time required for each activity and the temperature 

 and then similarly for humidity, will disclose temperature and humidity points 

 of maximum efficiency. With the boll weevil these points lie approximately 

 near 83° F. and 65 per cent of relative humidity." 



Hydrocyanic acid gas. — Its practical use as a routine fumigant, R. H. 

 Ckeel, F. M. Facet, and W. D. Wbightson (Pub. Health Rpts. [U. S.}, 30 

 {1915), No. 40, pp. 3537-3550, fig. 1). — Tlie authors here present the results of 

 19 practical experiments with hydrocyanic acid gas. 



The results of several experiments with decreasing amounts of chemicals 

 indicate that the use of 5 oz. of potassium cyanid to 1,000 cu. ft. of space is as 

 effective as twice that amount. " It was clearly demonstrated that the quickest 

 and best results were obtained by the use of powdered potassium cyanid, the 

 chemical action being much facilitated and more rapidly completed. . . . At- 

 tempts to destroy bacteria with this fumigant were unsuccessful. 



" It was noticed that where the rodents were allowed to run at liberty within 

 the room during fumigation, and in the cases of the more active ones in cages, 

 the effects of the gas were earlier apparent and more marked, and the rodents 

 succumbed more quickly. Any physical efforts of the rodents seemed to hasten 

 the effects of the gas, presumably by increased respiratory action. The cyanid 

 gas apparently diffuses very rapidly, rising first to the top of a closed space, 

 thence following along the walls to the floor, and finally reaching the center of 

 the space." 



Cyanid gas was found to be much more penetrating than sulphur dioxid, and 

 thus it is to be preferred for fumigating ships loaded with cargoes. From the 

 experiments it would seem that one-half hour is sufficient exposure when cyanid 

 gas is used as a fumigant, and that the increasing of this period to one hour 

 ought to suffice, even when unusually large spaces are fumigated. One of the 

 experiments indicates that holds of ships will not retain cyanid fumes so as to 

 be dangerous to life 30 minutes after the hatchways are removed. 



rifteenth. report of the state entomologist of Connecticut for the year 

 1915, W. E. Bkitton {Connecticut State Sta. Rpt. 1915, pt. 2, pp. VII+81-192, 

 pis. 17, figs. 6). — The first part of this report is taken up by a statement relating 

 to the finances and routine work, including the inspection of nurseries, of 

 imported nursery stock, of apiaries, etc. 



Reports of Gipsy Moth Suppression Work in 1915 (pp. 99-111) and of Brown- 

 Tail Moth W^ork, Season of 1914-15 (pp. 111-114), by W. E. Britton and I. W. 

 Davis, next presented, are followed by a report of Experiments in Controlling 

 the Cabbage Maggot in 1915, by W. E. Britton and Q. S. Lowry (pp. 114-118) 

 in continuation of investigations of 1914, previously noted (E. S. R., 33, p. 58). 

 The season was particularly favorable for control experiments, as the maggots 

 were very abundant and caused more damage than usual. The best results 



