2 BULLETIN 14, U. S. DEPARTMENT OE AGRICULTURE. 
THE MIGRATORY HABIT 
One need make only a few observations on the behavior of housefly 
larva? to discover an excellent example of what Prof. Howlett calls 
■'■'a sort of active hypnotic trance." This is to be found in the 
migratory habit which is so much in evidence during the prepupal 
stage. The habit has long been known and repeatedly mentioned 
hi the literature. Thus Xewstead (1907) 1 found that "deep down 
at the sides, in the cooler portions of the receptacles, the pupa or 
chrysalis stage occurred in enormous numbers, looking like small 
heaps or collections of reddish berries." 
Griffith (1908) found that "the larva? remained in the hottest 
part of the heap, but the pupa? were all found near the surface where 
it was cooler." 
Jepson (1909), in certain rearing experiments in winch moist- 
bread was used as food, found that "the larva? rarely left their 
feeding ground till fully fed, when they left the moist mass of bread 
for the surrounding dry area and there pupated." 
Herms (1911 1 states that "the growing stage requires from four to 
six days, after which the maggots often crawl away from their 
breeding places, many of them burrowing into the loose ground 
just beneath the manure pile, or crawling under boards or stones 
or into dry manure coUected under platforms or the like. * * * 
The larva? often pass three or four days in the prepupal or migrated 
stage before actually pupating." 
R. I. Smith (1911) says "it was very apparent that the maggots 
which swarmed through the manure were inclined to congregate 
hi certain corners or crevices and pupate in a mass. * * * Scat- 
tered pupa? were discovered around the edges of the piles of cow 
manure and even in the soil underneath where the maggots had 
burrowed before pupating." 
Hewitt (1912) states that '"when full grown the mature larva 
usually leaves the moist situation hi which it has developed for 
one of a drier nature, often crawling for several yards in search of 
some dry and sheltered crevice. Here it rests for a short time 
preparatory to changing into the pupal stage." 
If any further evidence were needed to demonstrate such an 
habitual mode of action I might mention the following observations: 
During the past few months it has been my duty to assist in carrying 
out an extensive series of experiments in testing the value of various 
chemicals in treating manure with a view to the destruction of the 
larva? present. The manure is placed in large cages and the chem- 
ical to be tested is sprinkled over it. The bottom of the cages con- 
sists of a galvanized iron pan with sides 1 foot high. In the floor 
of the pan are nine small holes. The sides of the cages above the 
1 Numbers in parentheses refer to dates in the bibliography, p. 11. 
