188 
OF INSECTS. 
IV. St. Pierre tells us,* that in a fly with six feet, (I 
do not remember that he describes the species,) the pair 
next the head and the pair next the tail, have brushes at 
their extremities, with which the fly dresses, as there may 
be occasion, the anterior or the posterior part of its body; 
but that the middle pair have no such brushes, the situation 
of these legs not admitting of the brushes, if they were 
there, being converted to the same use. This is a very ex¬ 
act mechanical distinction. 
V. If the reader, looking to our distributions of science; 
wish to contemplate the chemistry, as well as the mechan¬ 
ism of nature, the insect creation will afford him an ex¬ 
ample. I refer to the light in the tail of a glow-worm,. Two 
points seem to be agreed upon by naturalists concerning it: 
first, that it is phosphoric; secondly, that its use is to 
attract the male insect. The only thing to be inquired 
after, is the singularity, if any such there be, in the nat¬ 
ural history of this animal, which should render a pro¬ 
vision of this kind more necessary for it than for other 
insects. That singularity seems to be the difference which 
subsists between the male and the female; which difference 
is greater than what we find in any other species of animal 
whatever. The glow-worm is a female caterpillar ; the 
male of which is a fly; lively, comparatively small, dis¬ 
similar to the female in appearance, probably also as distin¬ 
guished from her in habits, pursuits, and manners, as he 
is unlike in formrand external constitution. [PI. XXXIII. 
fig. 4, 5.] Here then is the adversity of the case. The 
caterpillar cannot meet her companion in the air. The 
winged rover disdains the ground. They might never 
therefore be brought together, did not this radiant torch 
direct the volatile mate to his sedentary female. 
In this example, we also see the resources of art antici¬ 
pated. One grand operation of chemistry is the making 
of phosphorus: and it was thought an ingenious devise, 
to make phosphoric matches supply the place of lighted 
tapers. Now this very thing is done in the body of the 
glow-worm. The phosphorus is not only made, but kin¬ 
dled; and caused to emit a steady and genial beam, for 
the purpose which is here stated, and which I believe to 
be the true one. 
VI. Nor is the last the only instance that entomology 
affords, in which our discoveries, or rather our projects, 
turn out to be imitations of nature. Some years ago, a 
*Vol. i. p. 342. 
