G. S. Graham-Smitii 
503 
provisions to prevent migration have to be made, if any conclusions 
are to be drawn as to the numbers of flies developing from various 
masses of food. The tendency to migrate is most marked in the older 
larvae, but even very small ones migrate under certain conditions. 
The eggs are generally laid under the edges of pieces of meat, on the 
hair of animal bodies close to the ground or in the mouth, nose, ears or 
anus. Maggots usually feed under the skin or in the interior of carcases, 
but live freely on the surface, if the food is in darkness, and disappear 
into the depths with remarkable rapidity when it is exposed to the light. 
According to the observations of Portchinsky (1913) and of Keilin 
(1915) the larvae of several of the common species of flies feed on the 
larvae of other species. Placed in order of the abundance of the adults 
the most important carnivorous larvae are those of Hydrotaea dentipes, 
Muscina stabulans, Graphomyia maculata, Polietes albolineata, Phaonia 
enatica and Azelia macquarti. 
The enormous destruction of the larvae of common flies wrought 
by the larvae of //. dentipes alone has not been taken into account 
hitherto. Such carnivorous larvae must be extremely important 
natural agents in limiting the numbers of many of the species hkely 
to carry pathogenic and putrefactive bacteria to human food. 
On July 7 a large piece of sheep’s lung containing some eggs 
and very small larvae was buried to a depth of 1| feet, and the earth 
well packed down. The earth was further trodden down on July 9. 
On July 12 the material was exhumed and numerous large, apparently 
healthy larvae were found in it. 
Later a series of similar experiments were carried Out to ascertain 
the effects of burial on larvae. 
On September 4 the bodies of six guinea-pigs were exposed. On 
the same day one of the carcases with eggs in the mouth and on the 
hair was buried to a depth of a foot in an earthenware pipe sunk 
vertically in the ground. A little earth was placed above the carcase 
and packed down tightly, and the process repeated till the pipe was 
full. The top of the pipe was sealed with an earthenware saucer. 
The other carcases containing larvae of various sizes were similarly 
buried on September 8, 10, 11 and 14. On September 26 large full fed 
larvae and pupae were noticed just below and on the surface of the 
earth in all the pipes. Blow-flies began to emerge simultaneously from 
all the pipes on October 17, and large numbers were caught up to 
October 29, and smaller numbers up to November 15. 
These observations show that larvae emerge from eggs and thrive 
