452 INSECTS INJURIOUS TO VEGETATION. 



the approaching change being marked by an alteration of the 

 color of the anterior segments, which from orange become red, 

 shining, and swollen, as if distended with blood. "Within a 

 few hours after this change of color, rudimentary legs, wings, 

 and antennae, begin, as it were, to bud and put forth, and 

 rapidly grow to their full pupal dimensions; and thus the 

 transformation to the pupa is effected without any moulting 

 of the skin of the larva. In a few days, the pupa works its 

 way upwards, bursts through the silken film, and rests half 

 way out of the orifice of the beaked summit of the gall, where 

 it casts off and leaves its pupa-skin, and appears in its winged 

 form. This little gnat or fly is of a deep black color above, 

 paler and downy beneath, with livid legs and smoky wings. 

 The length of its body is a little over one fifth of an inch, and 

 its wings expand rather more than three tenths of an inch. 



The Cecidomyia Robinicc, of Professor Haldeman,* is a much 

 smaller and more common species, inhabiting the locust-tree. 

 During the month of August, some of the leaves of this tree 

 will be found to have one edge thickened in substance and 

 rolled over, so as to form an oblong cavity, cylindrical in the 

 middle, and tapering at each end. This is the work of the 

 larvoB or young Cecidomyians, two or three of which will 

 sometimes be found in each cavity, where also they complete 

 their transformations. The larva is a maggot of a whitish 

 color, faintly tinged with orange, particularly towards the head. 

 The pupa or chrysalis is not contained within a cocoon. The 

 fly measures three twentieths of an inch in length. It is orange 

 colored, with dusky antennas and wings, three dusky lines on 

 the thorax, and two dusky spots on the sides of the body. An 

 apparent interruption in one of the veins of the wings, noticed 

 by Professor Haldeman, is not peculiar to this insect, but may 

 be seen, more or less distinctly, in our other species of Ceci- 

 domyia. 



The Hessian fly was scientifically described by Mr. Say, in 

 1817, under the name of Cecidomyia destructor.^ It obtained 



* " American Journal of Agriculture and Science," Vol. VI., p. 193. 

 t " Journal of the Academy of Natural Sciences, of Philadelphia." Vol. I., 

 p. 45. 



