CECIDOMYID^. 373 



sometimes provided with bristles or horny spinules, frequently 

 curved, which aid the larvae in leaping, as they have been 

 observed by Dufour to do. The head and mouth-parts are 

 exceedingly rudimentary, consisting of a ring with two pro- 

 cesses extending backwards ; the soft fleshy labium protrudes 

 through this ring ; and from the upper part of the ring 

 arise a pair of two-jointed organs, supposed to be rudimental 

 antenuse. On the under side of the body at the juncture of 

 the first or prothoracic segment with the supernumerary seg- 

 ment, is a horny piece called, provisionally, the breast-bone 

 (Fig. 284, a), and which is present in most of the larvae of this 

 group. The larvae having no jaws, must suck in the sap and 

 moisture through the mouth, or aljsorb it through the skin. 

 The}^ make no excrement, like the larvai of the Hive bee and 

 Humble bee. Though their motions are ordinarily slow, just 

 before pupation they are very active. The larvae are not 

 known to moult, though probably the larva skiu is shed by 

 gradually peeling off in shi'eds, in this respect resembling the 

 thin-skinned larvae of bees. 



Some larvae of Cecidomyia before becoming pupae, leave 

 their galls and descend to the ground, while others remain in 

 them, where they spin a slight silken cocoon. Dr. Harris has 

 described the mode of pupation of the larva of C. salicis Fitch, 

 stating that "the approaching change is marked by an altera- 

 tion of the color of the anterior segments of the larva, which 

 from orange become red and shining, as if distended l)y 

 blood. Soon afterwards, rudimentary legs, wings and antennae 

 begin, as it were, to bud and put forth, and rapidl}' grow to 

 their full pupal dimensions, and thus the transformation to the 

 pupa is completed." This process is undergone beneath the 

 larva skin, out of which the pupa does not draw its body, as in 

 the obtected diptera generall}-. The larva skin, dried and cy- 

 lindrical in shape, thus serves as a cocoon to preserve the soft 

 pupa from harm. The semipupa of C. destructor thus "takes 

 the form and color of a flax-seed. While this change is going 

 on externally, the body of the insect gradually cleaves from its 

 outer dry and brownish skin. AVlien this is carefull}^ opened, 

 the included 'insect will be seen to be still in the larva state.* 



*This "lai-va" is probably the .«emii)npa, or "be^'iimiiig of the pupa state" 

 (Harris), and may be compared with tlic semipupa of the Bee. (Fig. 27.) 



