Studies on the mouth parts and sucking apparatus in the blood-sucking Diptera. No. 3, Lyperosia minuta, Bezzi / by F.W. Cragg.

  • Cragg, F. W. (Francis William), 1882-1924.
Date:
1913
Catalogue details

Licence: In copyright

Credit: Studies on the mouth parts and sucking apparatus in the blood-sucking Diptera. No. 3, Lyperosia minuta, Bezzi / by F.W. Cragg. Source: Wellcome Collection.

    35/76 page 25
    the lower end there appears a separate piece, oval in outline, pointed at its ends, and almost filling up the interval between the two lateral walls in this situation. In the next few sections this piece enlarges, becomes more rounded, and is more and more closely approximated to the lateral plates, until it fuses with them. The distal end of this free piece is situated at the point where the two lahella fuse with one another on the posterior surface, and it can he seen jn this situation in cleared preparations. As it broadens out distally the two lateral halves become a little separate from one another, and a small amount of loose cellular tissue appears in the space. In the sections proximal to this point there is a rapid change in the appearances, once we pass to the upper end of the discal sclerite. Figure 16, Tlate III, represents a section just behind the point where the free median plate has fused with the lateral plates. We see here that the external plate has undergone a considerable change and now presents an irregular outline, marked by two furrows on either side of the middle line; the median portion of the sclerite is now fused to the lateral portions, and shows some loose cells in its in- terior. The two plates of the sclerite are now divided into an upper and a lower portion. A few sections distal to this the division commences at the upper limit, and passes down as we progress from the lahella to the labium. In the middle of the lower portion of the section there appears another free piece anterior to the one already noted, as shown in the figure. We have therefore two lateral and anterior portions, a U-shaped lower or posterior plate> and a middle piece fused in the angle between them, and now another piece of solid yellow chitin anterior to this. The two lateral pieces are the ends of the upper portions of the labial gutter, the anterior piece in the middle is the end of the middle portion of the gutter, and the rest belongs to the discal sclerite. As we pass upwards from this point the discal sclerite becomes steadily reduced in size while the labial gutter comes to occupy more and more of the section. In the next figure (Fig. 17, Plate III) we see that the anterior middle inece has increased in breadth and in depth, and the vertical extent of the lower U- shaped piece has become much less, and at the same time it is wider. The gutter rests on two notches on the inner sides of the sclerite, which is here rather Y-shaped. In the next figure, which represents the next proximal section, the middle portion had definitely assumed the shape of the gutter, and has become connected with the ends of the lateral portions, while it is embraced by the now rather wider part of the sclerite. Still higher up the sclerite be- comes much thinner and recedes behind the gutter, where it appears as a wide arch. A few sections higher up it appears only as a narrow arched hand behind the gutter, the two portions of which remain quite separate from one another. Above this it ceases, and at the level of the furca (Fig. 21, Plate IY), the two
    digitised image 1
    digitised image 2
    digitised image 3