; 



INSECT ECOLOGY 359 



The eggs are not in the same stage of maturity at the time of oviposition, 

 as at 24 F. we have from 9 to 18 days as the length of the stage." 



As regards the threshold of development, Sanderson found that eggs 

 of the meal worm, Tenebrio molitor> failed to hatch at 9 or 10 C. but 

 hatched at 12 C. 



The time from the deposition of the eggs to hatching of the chinch 

 bug is variable, being longer if temperature is low, or shorter if high. 

 Thus first brood eggs (June) with an average mean temperature of 73 F. 

 hatch in 17.3 days; and second brood eggs (August) at 76.58 F. in 11.45 

 days; the average for both broods being 14.4 days (Headlee and 

 cColloch). 



Larval Development. The discussion already given of growth and 

 evelopment in relation to temperature applies of course to the larval 

 tage as well as to all other stages of development. 



Larvae of the cotton boll weevil in squares developed in 7 days at 

 n average mean temperature of 75 F.; the total of effective tem- 

 ratures being 280 degrees F. (Hunter and Hinds.) 



The bollworm, or corn ear worm, developed in 21 days at an average 

 mean temperature of 77 F.; the total of effective temperatures being 

 17 degrees F. (Quaintance and Brues.) 



In these experiments it was assumed, as was formerly customary, 

 that only temperatures, above 43 F. were effective for growth; this is 

 known, to be a mistake. A small percentage of boll worms survive 

 a temperature of 34 F. ; but larvae subjected to temperatures somewhat 

 below freezing for one to two days are killed outright. 



A constant temperature of 90 F. prevents the development of the 

 plant louse, Aphis avence; the optimum temperature for the production 

 of the wingless agamic forms being about 65 F. (H. E. Ewing.) 



Warmth and dryness are favorable to the development of species 

 of "thrips" (Thysanoptera) and of the "red spider," a well known 

 mite that injures plants, especially in greenhouses. 



Molting. In the walking-stick, Diapheromera femorata, a low tem- 

 perature lengthens, while a high temperature shortens, on an average, 

 the interval between molts. A low temperature has a tendency to 

 decrease the number of molts, while a high temperature increases the 

 number. (H. H. P. and H. C. Severin.) 



Pupal Development. Krogh found that the extremely simple 

 relation (already described) between temperature and the velocity of 

 embryonic development held good also for the changes taking place 

 during the pupal life of the meal worm, Tenebrio molitor. He says: 



