394 TRANSFORMATIONS OF INSECTS. 
The Cecidomyide are very small Diptera which, like the Cyzzps, 
produce galls on plants in which their larve live. Nevertheless, 
there are exceptions to this gall-making peculiarity, for the wheat 
fly, Cectdomyia tritici, lays its eggs in the centre of the flower of 
the wheat plant, and when its larve are hatched they eat the 
pollen, and thus prevent the formation of the corn. An American 
species, which is known by the name of the Hessian Fly, attacks 
the lower part of the stem of the wheat plant, and the larva 
Cecidomyta WITH VIVIPAROUS LARV. 
nourishes itself with the sap, which it appears to take by suction, 
and causes the stem to wither and die. 
A very interesting discovery has been made by Nicholas 
Wagner, a professor at Kazan, to the effect that the larve of 
some species of Cectdomyia which live underneath the bark of 
trees have the power of producing creatures like unto themselves. 
In the centre of the engraving there is a representation of the 
adult insect, and on either side of it drawings of the nymph, and 
below the larva is depicted, and it will be seen to contain at aa 
