The Book of the Fly / A nature study of the house-fly and its kin, the fly plague and a cure

by George Hurlstone Hardy

B = the Thorax, the middle portion of the fly bearing the organs of locomotion.

B, I, the Dorsum. The diagram on plate VI, fig. 40 illustrates the upper surface of this region; this part is bounded in front by (a) the Neck; behind by (b) the Scutellar Suture (15) or Seam; at the sides by (c) the Dorso-pleural Sutures (9-9) running from the front corners to the front of the Wing Bases; by (d) the Wing Bases (10-10); and by (e) the Scutellar Bridges, which are ridges (11-11) running with right and left inclines to the root of (6) the Scutellum. The Dorsum is crossed by (8) the Dorsal Suture, behind which are the Alar Regions (5-5); here on each side is a ridge (12-12) the Alar Frenum; rows of minute bristles on the centre are termed Acrostichal.

B, II, the Sides, or Pleuræ, specified separately in connection with—

B, III, the Breast, or Sternum; (1) the Prothorax is below the shoulder and above the fore-leg; (2) the Meso-pleura is contiguous to the prothorax and the shoulder; here in the upper front corner is the "Stigma," a prominent respiratory orifice, below which the large Stigmatical Bristle may be found; the (3) Ptero-pleura is below the wings and behind the meso-pleura; (4) the Meta-pleura is "a more or less tubercular piece below the region between the root of the wing and the haltere"; (5) the Sterno-pleura is above the middle leg and below the Sterno-pleural Suture, where it bounds the meso-pleura; (6) the Hypo-pleura is behind the sterno-pleura and above the hind leg.

B, IV, the Meta-Notum is the part of the thorax behind and beneath B, I (6), the scutellum.

C = Appendages of the thorax.

C, I, Fore-legs, Mid-legs, and Hind-legs; every leg has nine joints [particularised illustrations on plate VII]; (1) Coxæ are the joints attached to the body; (2) Trochanters very small and inconspicuous; (3) Femora or Thighs; (4) Tibiæ or Shins; (5) First Tarsal Joint or Metatarsus; (6) Second Tarsal Joint; (7) Third; (8) Fourth; (9) Fifth Tarsal Joint; (10) the Knees are where the Thighs and Shins join; (11) Claws, Foot-pads, and Empodium are appendages of the fifth tarsal joint.

C, II, Wings [see Table of wing-cells and veins]; the quarters of the wing are the Fore and the Hind Basal Regions and the Fore and the Hind Apical Regions. The Stigma is a thickened portion of the wing at the middle of the fore margin.

C, III, the Halteres.

C, IV, Squamæ are scale-like appendages beneath the wings and above the halteres; they seem to have some attachment to the roots of the wings; a small inner lobe is called the antisquama, but it is a feature not of much use in classifying and differentiating species.