April, '10] SANDERSON : TEMIT^KATURE AND INSECT GROWTH 



121 



normal conditions, record of which we 

 have, have been maintained. In exact 

 Avork to determine the effect of temper- 

 ature the moisture conditions should be 

 constant, as with many species the mois- 

 ture influence is as much or more impor- 

 tant than that of temperature in determin- 

 ing the optimum for development. 



Similar observations on the time of 

 hatching of the eggs of Malacosoma ameri- 

 cana, the time of emergence of the cater- 

 pillars of the brown-tail moth from their 

 winter nests, the hatching of eggs of the 

 gypsy moth, and the pupal stage of Samia 

 cecropia, Papilio asfcrias and Epargyreus 

 tityrus, have been or are now being made, 

 but cannot be summarized at present. 



Other data is at hand, however, show- 

 ing the same facts. Thus Kerschbaumer 

 (15) has given data from which the curve 

 for the life cycle of Culex pipiens as in- 

 fluenced by temperature has been plotted 

 (figure 12), and Regener (21) and Ratze- 

 burg (20) have shown the same for the 

 different stages of Dendrolimus pini, 

 shown in figure 13. One of the most care- 

 ful studies of the relation of both temper- 

 ature and moisture to the development of 

 an insect is a recent one of Hennings (9) 

 with Tomicus typographus Linn. Hen- 

 nings reared all stages and secured the 

 complete life cycle of this species at four 

 different temperatures with 55% and 96% 

 moisture. Figure 14: sliows the curves 

 plotted from his data and shows graph- 

 ically the effect of moisture as related to 

 temperature for the species. Hennings 

 points out that no thermal constant for 

 the development of the species, which sev- 

 eral European students of forest insects 

 had endeavored to determine, could pos- 

 sibly exist as at 24° C. there would be an 

 accumulation of 624° when at 14° C. it 

 would amount to 1400.° 



Other activities of insect life as related 

 to temperature show similar curves, one 



10' 20° 80° C. 



Days 



s? 



^'^?E 



EHfe 



mi 



m 



Fig. 13. Relation of tem- 

 perature to development of 

 Deudrolinnis phii, from data 

 quoted by Bachmet jew ; egg, 

 pupa and larva from Rege- 

 ner, 1865; larva plus pupa 

 from Ratzeburg, 1839 (origi- 

 nal.) 



