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€ggs in one place on manure piles. This habit of association continued 

 to some extent in the lai-val stage, though it was probably dependent 

 on suitable feeding places. Numbers of larvae were observed to 

 pupate in one place, probably that which offered the least resistance 

 in migrating and which furnished proper protection and moisture. 

 The total period from the deposition of eggs to the emergence of the 

 adult varied from 8-51 days ; a much longer time was observed in 

 the hibernation experiments at Dallas and Uvalde, Texas. During 

 the coldest weather, development was completely arrested. The 

 incubation period of the eggs was in almost all cases less than 24 hours ; 

 the time of emergence of the larva was hastened by increase in tem- 

 perature. The larval stages lasted from three days to about three weeks, 

 the usual time being 4-7 days. Temperature, character and amount 

 of breeding mediumVere important factors. In large piles of manure, 

 it was observed that the larvae governed their temperature conditions 

 by penetrating further into the manure during cold weather and 

 remaining nearer the surface w^hen the weather was w^arm. The pupal 

 stage ranged from 3-26 days. The influence of temperature is more 

 marked in this stage than in the previous one, since the pupae are 

 usually more removed from the heat of the manure, and have no way 

 of accommodating themselves to changes of temperature. Horse 

 manure is a very favourable breeding medium ; manure of the chicken, 

 pig, goat and cow are also suitable. Decaying vegetable matter affords 

 important breeding places, especially in the neighbourhood of 

 towns. In the grain belt of Texas, Oklahoma, and the States to the 

 north, the rotted bases of oat or wheat straw stacks were found in 

 some cases to breed many house-flies ; fermenting cotton-seed husks 

 mixed with bran, etc., in the bottom of feed boxes produced very large 

 numbers. In experiments conducted in England, Dr. Hewitt found 

 it possible to keep house-flies alive for seven weeks in summer. Dr. 

 Griffith, also in England, had one fly live for 16 weeks. In the experi- 

 ments at Dallas, the maximum period was 53 days. The longevity 

 was greatly reduced when food was not given. During summer, when 

 supphed with abundance of food and breeding material, the usual 

 period was 2-4 weeks ; cold weather prolonged the hfe of the adults, 

 correspondingly delaying reproduction. It has been assumed that 

 the winter is'passed in the adult stage only ; evidence for this belief 

 has been drawn from the fact that flies dissected in autumn had much 

 fat stored up, while in spring this was absent. Adults have been found in 

 dormant, semi-dormant and active states in mid-winter, and those 

 emerging late in the autumn show greater longevity. The experiments 

 at Dallas show that the winter can be passed in immature stages ; 

 moreover, no adults under observation survived the winter. Results 

 indicated that flies kept at a temperature not low enough to render 

 them inactive either oviposited very soon or died. The chances of 

 adults finding shelter from destruction by cold seem, in the opinion 

 of the authors, very small indeed ; although some individuals may 

 hibernate in this way, the species is dependent on those individuals 

 which pass the winter in the immature stages, or those which continue 

 to breed through the winter. Experiments were carried on at Dallas 

 during the winter 1913-14 to determine the abiUty of adults to pass 

 the winter. The fungus, Empusa muscae, caused the death of large 

 numbers ; frequent observations during winter and spring failed to 



