4 BULLETIN 1324, U. S. DEPARTMENT OF AGRICULTURE 



C, the optimum for larval development, the female lays from 9 to 

 15 eggs. When intermittent temperatures of 1° and 37° are imposed 

 for 24-hour periods throughout the life of the moth, it lives longer 

 and lays 25 to 35 eggs. At temperatures intermediate between 20° 

 and 37° not over 12 eggs are laid. The vital repose obtained by the 

 lower temperature prolongs the life of the moth and an increase in 

 egg production results. Temperature affects both the rapidity of 

 egg-laying and the number of eggs deposited by Phthorimaea oper- 

 cidella (29). Glenn (28) states that low temperature delays egg- 

 laying of the codling moth (Carpocapsa pomonella). Isely and 

 Ackerman (^), who have recently studied the oviposition of this 

 insect, could detect no serious check in egg-lajdng under optimum 

 light conditions till a temperature of 18.3°C. was reached. Below 

 this few eggs were laid and oviposition ceased entirely at 16.7° C. 

 The period of lughest night temperature occurs immediately after 

 sunset, which probably accounts for the heavy oviposition at this 

 time (Siegler and Plank, ?'.£). Sharma and Sen (72) found that 

 certain Indian mosquitoes preferred temperatures near 35° C. 

 for oviposition, and high or moderately high temperatures under 

 proper moisture conditions stimulate egg-laying in the house fly 

 (Musca domestica) (Bishopp, Dove and Parman, 8). It has been 

 shown by Roubaud (67) that Glossina palpcdis Desv., which de- 

 posits living larvse, is active in this respect between approximately 

 23° and 28° C, whereas at 30° C. reproduction is completely arrested. 

 Lysiphlebus tritici Ashm. (=Aph!dius testacerpes Cress.), a hymen- 

 opterous parasite of the green bug (Toxoptera graminum Rond.) 

 attempted to oviposit, but without success, at 1.7° C., the lowest tem- 

 perature at which the oviposition activity of this species was ob- 

 served (27). Temperature plays an important role in the oviposition 

 of Habrobracon brevicornis (Wesmael) (3J{.). Z 



HUMIDITY 



Humidity is an important factor in the egg-laying activities of 

 many if not most insects. Shelford (73) observed that tiger-beetles 

 require moist soil for oviposition. By increasing the atmospheric 

 moisture from 55 per cent to 96 per cent, egg-laying of Tomicus 

 typograplueus was delayed from 1 to 7 days (Hennings, 35). 

 Heavy precipitation delays oviposition in Carpocapsa pomoneMa, but 

 whether from the effect of the moisture or from mechanical effects 

 was not stated (Glenn. 28). High atmospheric moisture favors 

 oviposition in the blow-flies (Calliphora spp., Lucilki spp., 81), 

 and invariably increases the amount of egg laying in DrosophUa 

 ■melanog aster (1). It is also necessary for normal oviposition of the 

 house fly (8. 63. 64, 68). According to Roubaud (67), the deposition 

 of larvae by Glossina palpailis ceases when the atmospheric humidity 

 reaches the saturation point unless the fly has previously been sub- 

 jected for several days to an accelerating temperature (28° C). The 

 humidity of the usual habitat of this species is normally 90 per cent. 

 Certain species of mosquitoes and other insects which lay their eggs 

 upon the surface of the water probably develop a strong hydro- 



3 The correct name for the species used by Hase (ef. Die Naturwissenseha'ft, Jahn?. 

 11, Heft. 39. p. 801. 1023) is juglandis. 



