BY FREDERICK A. A. SKUSE. 49 



Head smal], i-etractile, provided with a pair of two-jointed 

 rudimentary antennte, and a soft fleshy protuberance regarded by 

 Ratzeburg as the labium, A slender coi'iaceous or corneous organ 

 rooted in the fii'st thoracic segment and projecting anteriorly, 

 terminating just behind the head, is styled the breastbone. "This 

 organ," remarks Baron Osten-Sacken, " the use of or the homo- 

 logy of which is unknown, is peculiar to the larvae of Cecidomyia, 

 and seems to be seldom wanting. It may be that this organ is 

 used for locomotion, although I hardly would consider it as homo- 

 logous with the pseudopods of the larvae of Chironomus and 

 Ceratopogon. If the supplementary segment (between the head 

 and thoracic division) be considered as a part of the head, this 

 breastbone might be taken for the mentum, iu analogy to the 

 horny mentum of the larvse of the Tipulariae. The form of this 

 organ is variable in different species ; sometimes it ends anteriorly 

 in two points, with an excavation between them ; sometimes in 

 one elongated point ; or it is serrated, etc." The terminal body 

 segment is frequently provided with stiff or horny processes, which * 

 are employed, by some species at least, as saltatorial organs. The 

 motions of the larvae are in the majority of cases very slow indeed, 

 though in some few species considerably accelerated ])y the pro- 

 vi.sion of i)ointed projections, or in some cases even pseudoj^ods, on 

 the underside of the thoracic and abdominal segments. 



In order to undergo its next metamorphosis the larva may leave 

 the gall or malformation it inhaVnts, and bury itself in the ground; 

 or it may inclose itself in a cocoon on the surface of a h af, or hide 

 beneath dry bark, in rotten wood, under leaves, «fec., according to 

 the species. Lasioptera vastatrix never once leaves the grass-stem 

 in which it is dejjosited as an egg, until it assumes the imago 

 state, and previous to turning into the chrysalis spins for itself a 

 filmy silken cocoon. Winnortz remarks that although it is true 

 that almost all the species belonging to the sub-genus Cecidomyia 

 lie in the pupa state in a white cocoon, he could not convince 

 himself that any cocoon was constructed of a veritable thread- 

 work, not even in the case of G. pini, which Dr. Locw contended 

 4 



