802 
| Assembly 
Another species is the blue-bottle-fly, Calliphora Vomitnria, Linn. 
This is much larger than either of the preceding, an 1 is often seen 
buzzing about in situations where fresh meat is exposed. Its thorax is 
of a black or blue-black color, and the abdomen or hind-body deep shin¬ 
ing blue. And a second species of the same genus, named Fulvtbarbis 
by Robineau Desvoidy, closely resembles it, but is readily distinguished 
by the color of the bristle-like hairs at the base of the head below the 
eyes, which are here of an orange yellow instead of a black color. 
These are the most common and best known European species of 
these carrion-maggot flies, but there are quite a number of others very 
closely allied to them, yet regarded as distinct by the naturalists of the 
present day. Our American species seem to differ scarcely, if at all, 
from those of Europe. A careful study, however, and comparison of 
foreign specimens with those of our own country, is necessary to deter¬ 
mine accurately the number of our species, and whether they are really 
identical with those of the old world. 
One of the most interesting traits in the habits of all the maggot- 
flies, is the unerring accuracy which the parent fly displays in selecting 
the appropriate nest for her offspring. Thus the egg of some genera 
are always placed upon decaying animal matter; others upon decaying 
vegetables, particularly mushrooms; and others still upon the dung of 
the cow-yard ; the parent in each case choosing out the spot where her 
young will find that kind of nourishment on which alone it can subsist. 
From the eggs thus deposited, and which are commonly called fly¬ 
blows, the larv* hatch. These are denominated maggots, in common 
parlance ; and they accelerate the decomposition of the substances on 
which they live, so rapidly, that they seem to have been designed by 
the Author of Nature expressly for consuming such substances, and 
thus preventing them from tainting and poisoning the atmosphere by 
their effluvia, to the extent that they would be liable to do if left to de¬ 
cay gradually, and exhale all the gases that would be formed by their 
decomposition. When the maggots have arrived to maturity, they 
leave the substance on which they have been living, and crawl slightly 
into the ground, where they change into pupa of a chestnut brown or 
black color, and of a form resembling that of a barrel. Here in the 
earth they lie dormant during the winter, and on the return of warm 
weather the perfectly formed and fully grown flies hatch from them. 
It is the species of the genera Lucilia and Calliphora more particularly 
whose larvae subsist upon cadaverous matter ; whilst those of the genus 
Musca live in dung-hills. In this last situation is cradled during its 
infancy that best known of all insects, our common house-fly, which 
Dr. Harris supposes may be distinct from the analogous species ofEu- 
