Royal Society. 489 
was hot, concealed themfelves, and kept little feparate aflem- 
blies in thefe chambers 5 atlaft, the empire becoming chriftian, 
they fell again into the old (late of negle6t, in which they con- 
tinued, until they came to be looked and fearched into. 
"The Libella, hy M. Poupart. Phil. Tranf. N'' 16 y p. (J) 5. 
TH E Libella is a flying infedl called in France Demoi- 
felle, from the variety of its colours, tranfparency of 
its wings, and its ftately nighty they alfo call it "Pearls 
from the figure of its head, or rather from the roundnefs 
and colour of its eyes ; it is divided from fpace to fpace 
into rings, by means of which it compofes angles with 
its body whofe lines it can make longer or Ihorter, as it finds 
occafion : Thefe different fcdions ferve to the motion of 
this infeft, as we know the tail doth in birds 5 and as they 
are lengthened or contracted, they convey themfelves at plea- 
fure, the point or centre being fix'd between their wings: 
All modern naturalifts know, that the greater fort of Libell<e 
are generated under water, being wrapt up in a membrane 
which at length diflblves : When the young Libella is ready 
to quit its cafe, it dilates its belly, that the water may enter 
at the ^;;//5 into the inteftines; then it comprefTes itlelf, in 
order to make this water circulate, which it expels and fhoots 
out a great way ; it receives more water into its inteftines, 
and ejeds it in the fame manner j and it continues this aflion 
with great force forfome time, and makes the water circulate: 
In order to fatisfy himfelf that it took in the water at the 
j4nus, and not at the mouth, M. Poupart put a Libella upon 
his finger, which he held faft by the legs 5 he plunged it under 
water with his head downwards, the y4nus being in a level 
with the water, fo that it might get into the inteftines, and 
this water it ejected a great wayj he drew his finger a little 
further out, fo that the water could not enter at the ^nus^ and 
the fly continued its motion, but ejedled no water : M. Pou- 
part thinks, that the animal does this, in order to cleanfe its 
body from all excrements in that element where it leaves its 
old robes, to appear in a more glorious, and new form in the 
open air: There are a great number of fmall veffels, which 
clofely unite the body of the Libella in its cafe 5 it is necef- 
fary that thefe be dry, that they may the fooner break, when 
it makes its efforts to get out of its cafe, which cannot 
happen, as long as there is any aliment in the inteftine to 
afford nourifhment to the cafe, and its ftrings 5 and perhaps 
Vol. III. CLq q ^^^ 
