INTERNAL ANATOMY OF INSECTS. 145 
flames; in colour it is most commonly white, but some- 
times yellow or green. It is imagined to be a kind of 
epiploon or caul, and is accumulated in the larva as a 
store of nutriment for the growth and development of the 
organs of the perfect insect while in the pupa state?. 
The blood in which the different organs float that is 
not required for their nutriment, is supposed to be ex- 
pended in the formation of this substance. Marcel de 
Serres is of opinion that it is secreted from the chyle by 
passing through the pores of the dorsal vessel, formerly 
called the heart of insects>. 
Under this head Imay mention what little is known with 
regard to the perspiration of these animals‘. ‘That a con- 
siderable quantity of fluid passes off from them when in 
the pupa state, is sufficiently proved by the loss of weight 
which they undergo, and by the experiments of Reaumur, 
who collected the fluid in closed glass tubes; and that in 
their perfect state they are constantly passing off per- 
spirable matter by the pores of their skin or crust, is not 
only rendered probable by the succulent nature of their 
food and the absence of any urinary discharge, but is 
proved by what takes place in a swarm of bees. ‘These 
insects, when crowded together in hot weather in a large 
mass, become heated to such a degree, and perspire so 
copiously, that those near the bottom are quite drenched 
with the moisture it produces, which so relaxes their 
wings that they are unable to fly*. 
* Reaum. i. 145. Lyonnet Anat. 106—. MN. Dict.d’ Hist. Nat. 
xvi. 224. Pirate XXI. Fic. 5. a. b See above, p. 89. note *. 
© See above, p. 78. 4 Huber i. 273, 
VOL. IV. L 
