Famity CALLIPHORIDAE 59 
PUPATION. Fraenkel (1935) stated ‘‘ Proofs have been estab- 
lished for the action of a hormone inducing pupation in the blow- 
fly. This hormone is secreted from 16 hours before pupation at 
20° C. The hormone producing organ is either the ganglion, or 
in its immediate neighborhood. After the hormone has already 
been discharged, pupation can be successfully accomplished with- 
out the cooperation of the nervous centers (ganglia).’’ 
PUPARIUM. The puparium is the sclerotized, more or less 
shrunken, cast skin of the third-instar larva. It therefore pos- 
sesses the major external characters of that instar and has been 
deseribed for only a few of the species. The depth in the soil at 
which pupation occurs may be characteristic of species within a 
genus, and this information is regularly given when known. 
ADULT HABITS. The adult blowfly usually emerges from the 
puparium in the morning. The metallic species are first grayish 
brown in color, then various metallic shades, and after a few 
hours are typically colored. Some of the species gradually 
change in color from yellow gray to bronzy green over a period 
of 3 to 4 days. 
Most of the species differ markedly from each other in adult 
habits. Some of these differences are so obvious that one can 
identify certain species in nature by flight habits or other essen- 
tial peculiarities. Some of these differences are discussed in the 
text under species headings. 
Individual blowflies may live for a considerable time in cap- 
tivity. Salt (1932) secured sterile eggs from a female of sericata 
91 days old and he reported upon another female which lived 
for 104 days. He found the average length of life in sericata to 
be 56.6 days in the female, 41.0 days in the male. 
Limited larval food supply and delayed pupation will cause 
variation in the size of adult blowflies. Delayed pupation will 
also result in the production of ‘‘monsters’’ manifest in wings 
that will not fold, lack of muscular coordination, or atrophy of 
abdomen or appendages. Individuals of this kind often emerge 
from puparia subjected to low temperatures and high humidi- 
ties. Such individuals die within a day or two. 
