58 INTERNAL ANATOMY OF INSECTS. 
each of which enters a branch of the false gill. These 
branches send forth on each side numerous lesser rami- 
fications, one of which enters each of the filaments?. In 
another species (Z. vespertina) each false gill presents 
the appearance of a pair of ovate leaves with a long 
acumen, and the air-vessels represent the midrib of the 
leaf, with veins branching from it on each side’; and, to 
name no more, in ZL. fusco-grisea, one branch represents 
the leaf of a Begonia, the sides not being symmetrical, 
with its veins, while the other consists only of numerous 
branching filaments*. In other aquatic larvee, as in that 
of the common May-fly (Sembiis lutaria Latr.), these ap- 
pendages consist of several joints*. 
By the above apparatus these aquatic animals are en- 
abled to separate the air from the water, as the fish by 
their gills; but how this separation is made has not been 
precisely explained. ‘The false gills in many species are 
kept in continual and intense agitation. When they 
move briskly to one side, Reaumur conjectures they may 
receive the air, and when they return back they may 
emit it®. This brisk motion probably disengages it from 
the water. In many species, when in repose, they are 
laid upon the back of the animal*, but in others they are 
noté. { 
The larvee of the Agrionide appear to respire like 
those of the Ephemera, &c. by means of long foliaceous 
@ Prare XXIX. Fic. 5. De Geer ii. 624—. 
> PrarE XXIX. Fic. 4. De Geer Jbid. 647—. 
* Pirate XXIX. Fic. 3. De Geer Ibid. 653—. 
“ Prate XXIX. Fic. 6. De Geer Ibid. 727—. 
© Reaum. vi. 465. " Ibid. i. xlii. f. 4, 5. De Geer ii. 623. 
= Tbid. 648. ¢. xvii. f. 11, 12. 
