336 



POPULATIONS 



In his experiments Lund controlled the 

 temperature at 25° C. and recorded the 

 number of progeny produced, and the lon- 

 gevity of males and females in four con- 

 ditions of humidity, namely: saturation 

 (0 mm.), and in saturation deficiencies of 



sexes is considerably reduced. "Since the 

 products of saturation deficiencies (govern- 

 ing rate of evaporation) and the longevi- 

 ties (duration of evaporation) at 10 and 

 15 mm. are about equal (43.0 and 45.0 

 respectively for the females and 44.0 and 



800 



> 



LU 600 

 LiJ 



UJ 



O 400 



O 



a: 



Q. 



o 

 (r 



UJ 

 CD 



200 



"^sTS'/o R.H. 



200 



400 



600 



800 



INITIAL DENSITY OF PARENT WEEVILS 



Fig. 125. Smoothed curves indicating the relation between parent weevil density, progeny, and 



relative humidity. (After Utida. ) 



5 mm., 10 mm., and 15 mm. His findings 

 are as follows: 



Humidity 



( Saturation 



Deficit) 



Factor Observed Mean ± S.E. 



mm Number of progeny 64.0 ± 1.7 



Male longevity ( days ) 6.8 ± 0.3 

 Female longevity ( days ) 5.2 ± 0.2 



5 mm Number of progeny 66.1 ih 2.5 



Male longevity ( days ) 6.3 ± 0.3 

 Female longevity ( days ) 5.7 ± 0.2 



10 mm Number of progeny 58.4 ± 2.R 



Male longevity ( days ) 4.3 ± 0.3 

 Female longevity (days) 4.4 it 0.1 



15 mm. Number of progeny 51.9 ± 1.2 

 Male longevity (days) 3.1 ± 0.2 

 Female longevity (days) 2.4 ±0.1 



Certain conclusions can be drawn from 

 the table. At saturation deficiencies of 10 

 mm. and 15 mm., the longevity of both 



36.0 for the males) the total amounts of 

 water evaporated from the parasites at 

 these two conditions were about equal. This 

 would indicate that in these cases the hmit- 

 ing lethal factor is probably desiccation 

 and that the desiccation Umit is around 44 

 mm-days" (pp. 433—434). Lund concludes 

 that since death in the 5 mm. saturation 

 deficiency experiments is similar to that in 

 saturated atmospheres (0 mm.), therefore, 

 under the former conditions, it cannot be 

 the result of desiccation, but is attributable 

 to some other factor. The efiFect of hu- 

 midity on productivity is less pronounced, 

 but the general trend is the same with a 

 progressive decrease in the number of prog- 

 eny after the 5 mm. saturation deficiency 

 level is passed. The differences between the 

 means 66.1 and 58.4 and between 58.4 and 

 51.9 are significant in relation to their 

 standard errors. 



