254 EXPERIMENT STATION RECORD. [Vol.43 



sects, but l>olo\v this point it takes a coniparutively long time to do so. Dal;i 

 are i?iven in the appropriate places. 



" Tlie amount of oxygen absorbed by live wheat of low moisture content is 

 greater than the anumnt of carbon dioxid given off. At about 30° C. [86° F.l 

 CuhintJra orysa gives off about 20.5 nig. (nearly a fifth of their own weight) of 

 carbon dioxid in 24 hours, and at 20 to 21° only about 9.38 mg. Weight for 

 weight C. granaria gives off rather less carbon dioxid than C. oryza, which is 

 to be accounted for by its less active habits. The respiratory quotient for 

 C. oryza is about 0.773 and for C. granaria about 0.815, indicating that the 

 respiratory processes of these insects are perfectly normal. 



" The complete absence of oxygen is alone sufficient to kill weevils without 

 taking into account the presence of carbon dioxid, though they ai-e able to 

 remain alive for a considerable lime when only small percentages of oxygen 

 are present. ~ The extent to which weevils are able to mnke use of oxygen in 

 sealed vessels depends upon the percentage of that gas initially present. 



"Carbon dioxid exerts a poisonous effect upon weevils apart altogether from 

 the question of diminished oxygen pressure. Thus at 30 to 31° C. orysa was 

 killed in less than 12 days in an atmosphere containing from 14.08 to 22.56 

 per cent of CO2, though 18.88 per cent of O2 still remained. Pure (moist) 

 carbon dioxid is less fatal in its effects than carbon dioxid with a small ad- 

 mixture of oxygen. Pure (moist) carbon dioxid acts almost instantaneously 

 as a narcotic, under the influence of which weevils may remain motionless for a 

 long time without losing their power of recovery." 



Report on the vitality and rate of multiplication of certain grain insects 

 under various conditions of temperature and moisture, A. Dendy and H. D. 

 Elkington (Rpts. Grain Pests (War) Com., Roy. Soc. [Lo7idon], No. 7 (1920), 

 pp. 52). — The results of the investigations here reported in detail have been 

 summarized as follows: 



" Under suitable conditions of temperature and moisture and with an abundant 

 supply of wheat, Calandra orysa and C. granaria show a very high rate of in- 

 crease and breed all the year round. The optimum temperature for the breeding 

 of C. oryza and C. (p'anaria is about 82° F., for Rhizopertha dominica somewhat 

 higher. At all temperatures and under all conditions, Avhen breeding takes place 

 at all, C. orysa increases much more rapidly than C. granaria, the maximum 

 observed for the former species being a 700-fold increase in 16 weeks, at an 

 average temperature of 82.5°. For this reason C. orysa is a more serious 

 danger than G. granaria, unless, indeed, in this country, the higher rate of in- 

 crease is counterbalanced by the higher death rate of the adults in winter. 



"At ordinary room temperatures in this country, both C. orysa and C. granaria 

 multiply only during the warmer months of the year, tlie lower temperature 

 limit for multiplication being probably about 65°, while for Rhizopertha it 

 Is probably about 70°. At ordinary room temperatures nearly all adults of 

 C. orysa are killed off during the winter, but large numbers of larviF survive 

 in the interior of the grains. The adults of C. granaria, on the other hand, 

 survive the winter in large numbers, the death rate being little, if any, higher 

 than at other times of the year. The adults of the three species show remark- 

 able differences in their susceptibility to cold. After being kept at a tem- 

 perature of 33 to 36° for 11 days, 91 out of 1(X) C. granaria recovered, only 3 

 out of 100 C. orysa showed very feeble signs of life, and none out of 100 

 R. dominica recovered. 



"/?. dominica is less susceptible to high temperatures than the two weevils, 

 the lethal temperature for an exposure of three minutes being about 146° 



