206 DISEASES OF INSECTS. 
This disease is not contagious, and is thought to be 
caused by a moist heat, attended by pernicious exhala- 
tions. La Luzette, Luisette, or Clairene, is another ma- 
lady, which shows itself most commonly after the fourth 
moult. It seems to arise from some original defect in 
the ege. The caterpillars attacked by it may be known 
by their clear red and afterwards dirty white colour ; 
their body becomes transparent, and the matter of silk 
exudes in drops from their spinnerets ; consequently, 
though as voracious as the rest, they are never able to 
construct a cocoon, and should be destroyed. Les Dra- 
gées is the name given to cocoons which include a larva 
that never becomes a pupa. ‘The cause of this disorder 
has not been ascertained, and whole broods are some- 
times subject to it, which, as in the last, seems to imply 
some defect in the eggs. But as the caterpillar spins its 
cocoon, and the silk is as good as usual, it is a malady 
of no great importance. Lastly, sometimes the mulberry 
leaves have a gummy rather acrid secretion, which 
purges the silk-worms; their excrement is no longer 
solid ; they become weak and languid; and if the secre- 
tion is abundant, their transpiration is impeded, and at 
the time of moulting they are become so feeble as to be 
unable to cast their skin?. 
In the case of many caterpillars of Lepidoptera that 
died, Bonnet found by dissection that the disease was 
remotely occasioned by a diarrhaa, which taking place 
immediately before they became pups, prevented the 
inner membrane of their intestines from being rejected, 
a Latr. Hist. Nat. xiv. 163—.° N. Dict. d’ Hist. Nat. iv. W34—— 
