OCR Text |
Show 266 INSECTA. ded transversely in the manner of a ring, or which are even composed of :five very distinct joints; but the sucker is formed of only four pieces, and the proboscis, the stem of which is usually very short, is almost entirely retracted within the oral cavity. The membranous nature of that organ and its turned up lips, its similarly raised and clavate palpi, the relative disposition of the wings which are usually crossed, the form of the abdomen which is rather oval or orbicular than triangular, and :finally the scutellum which is frequently armed with teeth or spines, also distinguish the N otacantha from the Tabanides. But few of their larvre have been observed. Such as have been discovered, are described and :figured by Swammer· dam, Reaumur and Rresel, are aquatic, and approximate to those of the Athericera in their soft head, varying in form, and in their habit of becoming pupre under their own skin; but they retain their primitive form and proportions, thus differing from those of the latter. Other larvre of the N otacantha-Xylophagus-live in the carious and diseased parts of trees. We divide the Notacantha into three principal sections. Those of the first--Mydasii, Lat.-never have teeth or spines in the scutellum. Their body is oblong, and the ab· domen forms an elongated and conical triangle. The wings are distant. Their antennre, from which we draw their most distinguishing character, are sometimes composed of :five distinct joints, the two last of which form a club in some, and the extremity of a cylindrical stem with a subulate termination in others, and sometimes of three joints, the last of which is largest, almost cylindrical, tapers to a point ~nd is divided into three annuli; thus these organs are always divided into :five. With the exception of Mydas in which the vestige of a very small stilet is perceptible, neither that appendage nor the seta which replaces it can be found in any of the Notacantha of this section; it is possible that the two last joints may represent them. In some the antennre are much longer than the head, con· DIPTERA. sist of :fi · · 267 ve JOints, are terminated in 1 ~y the two last, with an umbil' an e ongated club formed Issues a very short seta Th tcu~ at the end from which dentated or spinous on. the i=n~ost~riOr thighs are stout) and two peHets. The posterior cell: o~de. ~he tarsi have but or closed before the margin and the wmgs are complete or transverse. ' narrow or elongated, oblique These Insects compose the genus MYnAs, Which is divided into two subgenera. CEPHALOOERA, Lat. . Where the proboscis, is Siphon( 1) . in the form of a lo ng anc1 projecting MYDAs, Fab. 0~ Mydas proper, where that o . termmates by two large lips(2). rgan, as IS usual in this family, In the others, the antennre head, cylindrical and ta . are scarcely longer than the T ' permg to a · t h · he tarsi are furnished . th h pmn at t eir extremity. cells of the wings are long7t d' t ree pellets. The posterior rior margin. u Ina and closed by their poste- CHIROMYZA, Wied. Where the antenn::e are com o two last of which are the pllsed of five well separated joints the sma est(3). ' (1) A subgenus establish d (2) See Fab Lat de o? an Insect from the Cape . • , ., an particula 1 D 1 s~v~~ species. This sub enus an r y am.,. Dipt. Exot., 115, who describes dlVlsiOn, which, in a natu~ order d the preceding one appear to form a particular have some affinity with th f th, should perhaps be placed higher The . ( 3) w· . ose 0 e Pangonie • wmgs led.' Dlpt. E•ot I .. . • ' """ ., 'Vlll. |