﻿2 BULLETIN 14, U. S. DEPARTMENT OF AGRICULTURE. 



THE MIGRATORY HABIT 



One need make only a few observations on the behavior of housefly 

 larvae 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 

 in the literature. Thus Newstead (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 larvae remained in the hottest 

 part of the heap, but the pupae were all found near the surface where 

 it was cooler." 



Jepson (1909), in certain rearing experiments in which moist 

 bread was used as food, found that "the larvae 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) 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 collected under platforms or the like. * * * 

 The larvae 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 

 in certain corners or crevices and pupate in a mass. * * * Scat- 

 tered pupae 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 in 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 

 larvae 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. , 



