350 THE BLOWFLIES oF NortH AMERICA 
spring months females may be seen in considerable numbers fly- 
ing slowly over moist grassy areas. Many specimens, particularly 
males, may be collected upon umbelliferous flowers, where they 
are not easily disturbed while feeding. The species is apparently 
uncommon during midsummer, although it may frequently be 
collected in deep woods where numbers congregate about bases 
of trees. Most of the specimens that I have collected at this 
season of the year have been upon flowers of wild parsnip. Dr. 
C. H. Kennedy and I collected large numbers of adults upon 
parsnip during July in southern Ohio. Stewart (1930) reports 
collecting them upon Melilotus. 
Flies of the fourth and last generation of the year become 
numerous during the latter days of September and abundant by 
October 15. As cold weather progresses, both males and females 
try to find protection in trees, buildings, and under debris. In 
British Columbia, Dennys (1927) found that they hibernated 
in considerable numbers in the tunnels of wood-boring insects 
in Douglas Fir trees which had been killed by lightning, and 
which had a certain amount of loose bark and decayed wood. 
During 1916, Kisliuk conducted a series of trapping experi- 
ments with rudis. He exposed a large number of organic baits 
in traps and during the month of July, banana and milk and 
banana and vanilla extract attracted the species in considerable 
numbers. 
Economic wmportance. During the winter months hibernating 
adults of Pollenia rudis sometimes become a nuisance in house- 
holds, where they may be found in conspicuous swarms or clus- 
ters in closets, in unused rooms, or other retreats. Dall, Riley, 
Felt, and other North American economic entomologists have 
written upon this problem. Dall (1882) stated, ‘‘People soon 
learned to look for them (the flies) everywhere; in beds, in pillow 
slips, under table covers, behind pictures, in wardrobes nestled 
in bonnets and hats, under the edge of carpets, and in all 
possible and impossible places. A window easing solidly nailed 
on, will, when removed, show a solid line of them from top to 
bottom; they are uncanny. They like new houses, but are often 
found swarming in old unused buildings and go regularly to 
church, or perhaps only a few good ones abide in sanctuaries; 
anyway they are there. Best of all they like a clean dark cham- 
ber seldom used, and if not disturbed form in large clusters about 
the ceilings. They are very cold and feel in the hand like small 
bits of ice. They are very oily; if crushed, leave on the floor a 
great grease-spot.’’ Although the construction of the modern 
house has apparently eliminated much of the problem of the 
