XENOS PECKII.
Plate XXXIII. Fig. 2.
Linn. Trans. Vol. xi. Pl. 8, fig. 8.
Body brownish black; antennæ pale fuscous, almost diaphanous, sprinkled with minute white points. Wings ashy white, the anterior margin and nervures deep black, legs dull cinereous, tarsi dusky, extremity of the abdomen pale reddish. Length 1½ lines.
Larva and pupa found in Polistes fucata, an American insect.
Order IX.—Diptera.
This extensive order admits of a very brief and precise definition. The possession of only a pair of membranous wings, and a mouth formed for sucking, affords obvious characters for distinguishing it from all others. It is to the former peculiarity that the name refers, being derived from δις, twice, with the usual addition. Another marked singularity is to be found in the presence of two clubbed moveable bodies, termed balancers or halteres, projecting from each side of the thorax, and placed a little behind the wings.
The sucker attached to the mouth is composed of several slender pieces, from two to six in number, which are enclosed in, or rest upon, a fleshy proboscis or sheath, which gives support to them when employed, and also serves to pierce the cuticle of plants or animals, on the juice of which the insects live. When these pieces are six in number, they
