268 THE BLOWFLIES oF NortH AMERICA 
deposited over 3,000 eggs. The latter investigator found the 
average number of eggs produced at one time by females of 
sericata to be about 182, this number depending upon the size 
of the individual and therefore upon the amount of food obtained 
by it in the larval stage. 
Although some adults of sericata were found to migrate a 
maximum of 1.2 miles, Bishopp and Laake (1921) asserted that 
they had tested too few individuals to give reliable information 
on their disseminating tendencies. Smit (1929) stated, “‘It has 
been found that the flies will fly at least ten miles from their 
breeding place within a few days.’’ 
Wardle (19380) noted that the maximum abundance of sericata 
in nature might be expected in the vicinity of water courses in 
areas of low rainfall, in areas undergoing severe winter tempera- 
tures, and in urban districts where the prepupae have greater 
opportunities for securing positions of shelter from frosts. 
Specimens of adult. sericata may be collected in nearly every 
part of the United States and southern Canada, and during late 
June and early July this is the most abundant species of Phaens- 
cia in middlewestern United States. 
They frequent open habitation and are most active upon bright 
warm sunny days. Adults may be collected in abundance on al- 
most any kind of garbage, particularly when it is mixed with 
meats of various sorts or with damaged fruits. In urban districts 
they may be collected on foliage where they apparently feed upon 
honey dew. Considerable numbers may be found under leaves of 
cucumbers and melons, on leaves of vines and on flowers of wild 
parsnip and wild carrot. 
Economic wmportance. Reports of cutaneous myiasis caused 
by larvae of this species occur from almost the entire range of 
distribution of sericata. Bishopp (1915) stated that it ‘‘doubt- 
less is the principal cause of cases of blown sheep which occur 
in midsummer in this country.’’ Davies (1934) found it in 180 
of 182 cases of sheep strike in Wales, and Radcliffe (1935) ob- 
served that, with only one exception, sericata alone was involved 
in sheep strike. Lewis (1933, p. 264), however, did not find seri- 
cata to be an important species in Kenya Colony, Africa, and 
Mackerras (1937) noted that it was concerned in sheep strike 
during only 1 year at Sydney and Canberra, Australia, and then 
apparently as a secondary invader. 
As high as 92.6 percent of drying fruits were found by Dono- 
hoe (19387) to be contaminated by this and several other species 
of flies, and this is of considerable importance to fruit-drying 
industries in certain sections of California. 
