OF PAPILIONACEOUS INSECTS, _ 61 
instance of the Satyrus mera, Saturnia pavonia, 
and yarious others, the shells are furnished with a 
little lid, which, when the larva is completely 
’ developed, it can force up, and emerge at pleasure.* 
One of the most remarkable circumstances con- 
nected with the eggs of insects, is, their great specific 
gravity. From all the experiments which have 
been made, it has been found that they sink rapidly 
in water. This has been the case from the largest 
which has been tried, namely, those of the Drinker 
Moth, (Odonestis Potatoria,) which is almost the 
size of a hempseed, to that of the rose plant, Aphis, 
which is hardly yisible to the naked eye. But the 
eggas of the Gipsy Moth float, in consequence of 
their being covered with down. 
* Branam, 249. Roser. iv. 130. 
