32 MODERN CLASSIFICATION OF INSECTS. 
be applied, in allusion to the delicacy of the veins of the wings, which 
are moreover destitute of the numerous transverse veins near the pos- 
terior base of the fore wing, so conspicuous in E. vulgata. 
The pupa of another species, belonging to the genus Baetis, is 
figured by De Geer (vol. ii. t. 18. f. 1—4.), and is remarkable for the 
broad flat head, with short antenne, and large eyes; the prothorax is 
very broad and flat; the legs short, with the femora greatly dilated 
and compressed ; and the seven basal abdominal segments furnished 
on each side with a broadly oval gill, terminating in a point ; the six 
basal ones on each side being further furnished with numerous long 
flcating filaments, representing the other gill (fig. 61.18.) ; the tails 
are very long, and not fringed. My specimens (j/ig.61.17.) have the 
head and prothorax considerably broader than they are figured by De 
Geer, but in all other respects they correspond : in one of these which 
I dissected, I found the labium very large, completely covering the 
other parts of the mouth; the mandibles being small, but furnished 
at the base with a molary plate, as in the pupa of E. vulgata. 
Messrs. Goring and Pritchard (Nat. Hist. Obj. for Microscope, 1829, 
pl. 1.) have figured the pupa of a species which they named E. mar- 
ginata; but their figure of the imago represents it as 2-winged and 
9-tailed, thus belonging to the genus Cloeon. The head of the pupa 
(fig. 61. 20.) is small, scarcely more than half the breadth of the meso- 
thorax; the antenne as long as the body, about 24-jointed; the ter- 
minal joints being gradually elongated ; the legs long and slender, with 
2-jointed tarsi; the five basal abdominal segments furnished on each 
side with a pair of flattened membranous gills, each being very short 
(especially the basal one in each pair), the posterior one in each pair 
being of an elongated oval transverse form: the sixth abdominal seg- 
ment has on each side a single larger gill; the three apical seta are 
long, multiarticulate, and finely setcse; the central sete (as the pe- 
riod for assuming the perfect state approaches) becomes more trans- 
parent ; whereas the two exterior ones exhibit the two tails of 
the perfect insect inclosed in them. This pupa feeds on minute 
aquatic larvae, as well as on vegetables; the rapidity of its motions is 
astonishing, employing the six double paddle-like gills as oars, and for 
the purpose of balancing itself, and the posterior pair as paddles ; 
it likewise possesses the power of leaping or springing in the water to 
a considerable distance. I have observed these pupz to possess the 
power of darting both forwards and backwards with equal rapidity. 
This insect in its earlier larva state (in which the thoracic and basal 
