NOTES ON BIOLOGY OF SOME MUSCOID PLIES. — JOHNSTON. 93 



observed by him during the summer in Manchester were — 

 Egg, 8 hours ; first instar 24 hours, second 24 hours, third 3 

 days ; pupa 3 days ; total 8 days 4 hours, — but that probably 

 not less than 9 days, and commonly 10 or more, elapsed under 

 natural conditions. It should be mentioned, however, that 

 Griffith (1908) obtained a minimum of 8 days (egg to pupa 

 4| to 6 days, pupa to fly 3^ days) in the south of England. 

 The minimum obtained by Newstead (1907) in Liverpool was 

 10 days, as also was that recorded by Packard, observed in 

 Massachusetts, U.S.A. At an average daily temperature of 

 22-5° C. in England, flies require 14 to 20 days to emerge when 

 eggs were laid and the larvae developed in horse-manure 

 (Hewitt). 



The influence of moisture and temperature on the length 

 of the various periods in fly development has been studied by 

 Newstead (1907) and by Hewitt (1914). {See also Graham 

 Smith, 1914, p. 42.) Egg period at 10° C. 2 to 3 days ; at 

 15-20° C. about 24 hours ; at 25-35° C. 8 to 12 hours. Larval 

 period — first instar 20 to 36 hours or even to 4 days ; second 

 instar 24 hours (25-30° C.) to several days ; third instar 

 (including prepupal stage) 3 to 4 days (25-35° C.) ranging to 

 8 or 9 when conditions less suitable ; total larval period 

 5 to 8 days (when conchtions of temperature and fermentation 

 favourable) ranging to 8 weeks. Pupal period between 3 and 



4 days (at 35° C.) ranging to several weeks. The temperatures 

 mentioned (25-35° C.) approximately correspond with those 

 in tropical climates and in subtropical regions (such as Bris- 

 bane) during midsummer, and the results obtained by Hewitt, 

 using incubators, are similar to those recorded by Patton and 

 Cragg and by Smith for Indian conditions, and by us for 

 Eastern Queensland. 



Howard and Hutchison (1915, 1917) gave the larval 

 period (including egg stage) as 4 to 5 days under favourable 

 conditions in U.S.A. ; pupal 3 to 10 days in midsummer (up to 



5 months during midwinter) ; and mentioned that the shortest 

 time recorded as elapsing between egg deposition and adult 

 emergence in U.S.A. was 8 days, records of 10 to 12 days 

 being common ; and that only 3 or 4 days were needed during 

 midsummer for females to reach maturity after emergence. 



This preoviposition period, as it has been named, has been 

 carefully studied by Hutchison (1916), who attempted to 

 represent graphically its relation to temperature. The time 



