STRUCTURE, DEYELOrMENT, AND DIONOMICS OF HOUSE-FLY. 413 
one of the colleges (Cambridge), and were transferred to a 
small experimental greenhouse in the laboratory where the 
temperature was from 65° F. in the morning to 75° F. in the 
evening. The flies Avere allowed to oviposit in moist bread in 
which the process of fermentation had begun. He found 
that the times for the developmental stages approxi- 
mately agreed with those obtained by me at about the same 
temperature, and that the whole development was completed in 
about three weeks. At an average temperature of 70° F. the 
eggs Avere all hatched in twenty-four hours. The first larval 
stage lasted thirty-six hours, the second larval stage four 
days, and the third stage was complete in five and a half 
days; the Avhole larval period, therefore, occupied eleven 
days, fl'he average period occupied in the pupal stage Avas 
ten days; some puprn incubated at a temperature of 77° F. 
hatched in three days. 
It may be stated uoav, therefore, without fear of contra- 
diction, that flies are able to breed during the winter months, 
if the necessary conditions of food, temperature, and moisture 
are present. It is probablj'^ from these Avinter flies that the 
early summer flies are produced, as I have previously sug- 
gested. 
Corrigendum. 
My attention has been very kindly called by Prof. W. A. 
Riley to a slight mistake that I have made in my account of 
the venation of the Aving (Part I, p. 412). B}' an 0 A"ersight 
I have termed transverse nervnres the two small veins 
m.cu. (medio-cubital) and cu.a. (cubito-anal) . These ai’e 
really parts of the original longitudinal veins il/. 3 and Cu. 2. 
A study of such a series of dipterous Avings as those figured 
by Comstock in the papers there quoted (Comstock and 
Needham, 1898), or in his ‘Manual for the Study of Ento- 
mology,’ Avill shoAv that these ap])arent transverse or cross- 
veins are morphologically equivalent to branches of the 
primary veins. 
The University; 
Manchester. 
