Internal Structures of Tabanus Atratus: Detailed Views and Measurements

1. B Tabanus atratus #31: A, enface view (cuts along dashed lines made to view internal structures); B, left lateral view; C, enlarged cibarial dilator muscles. Spmn. courtesy E. Dotseth. A C

2. c Tabanus atratus #31 fc v * p e 8790 um Legend: c, cibarium; e, epipharynx; fc, food canal; p, posterior region of head capsule; v, vestibule. Note: all measurements in um. v = 410 fc = 3326 e = 424 c = 1484 p = 3326 Total = 8970 minus e/c overlap* of 180 = 8790

3. c Tabanus atratus #31 (#17 proportion) fc v * e 5806 um Legend: c, cibarium; e, epipharynx; fc, food canal; m, “mouth”; v, vestibule; *is overlap of c with e. Note: all measurements in um. v = 446 fc = 3518 e = 457 (* = 201) c = 1586 Note: consider that cibarium length is ≈ 40% of v + fc length (see previous slide).

4. revised to fit graphic c Tabanus atratus #31 (#17 proportion) fc v e 6055 um Legend: c, cibarium; e, epipharynx; fc, food canal; m, “mouth”; v, vestibule. Note: all measurements in um. v = 446 fc = 3518 e = 446 c = 1645 Note: consider that cibarium length is ≈ 40% of v + fc?

5. m = “mouth” or opening into cibarium m

6. 1 2 3 m 920 u m Tabanus atratus #31; epipharyngeal region. Distance from distal tip of “Y-bar” to first sensilla of the “median patch” ≈ 920um. Arrows: 1, proximal terminus of food canal; 2, distal extent of cibarium (dorsal, or “anterior” wall of Snodgrass, 1935); 3, salivary pump. Note that salivary pump lies below cibarium and is attached to cibarium by prominent musculature (m). Oval indicates “functional mouth” (of Snodgrass, 1935). Note that median patch of sensilla lies immediately in front of the “mouth.”

7. Tabanus atratus. Yellow ovals indicate opening into cibarium (i.e., the “mouth”). Black ovals: 1, median patch of sensilla; 2, posterior opening of cibarium emptying into pharyngeal pump. lateral view 2 Legend: c, cibarium; e, epipharynx; mx, bases of maxillae; sc, salivary canal; sp, salivary pump (lying below cibarium), see p. 318, Snodgrass 1937. mx 1 sc e c sp 0.84 mm mx dorsal view oblique view

8. Snodgrass (1935, p. 320) notes that the mouth (m) is a “functional mouth aperature” (not a true mouth). The true mouth (l in our plates) being, “…the opening into the stomodaeum at the inner end of the pump.” m l lw l mf aw aw l pw “The posterior and wide lateral walls of the organ are strongly sclerotized and fixed to the upper end of the labrum. The anterior wall, on the other hand, is thin and flexible and is ordinarily deeply invaginated into the lumen of the pump, but it is provided with two large groups of muscle fibers taking their origin on the median clypeal plate of the head wall ….. and is thus capable of exerting a sucking action on the liquid food ascending to the mouth through the food canal of the mouth parts.” Snodgrass, 1935, p. 320. Note: the “organ” is the cibarium; posterior and lateral walls (pw and lw); anterior wall (aw); mouth (m); and muscle fibers (mf), or cibarial dilator muscles; lumen (l). aw

9. c sc c sg sp lateral view dorsal view See Snodgrass (1935, pp. 318-319) for description of salivary glands. sp o Tabanus atratus. Legend: c, cibarium; o, openings of sg’s into sp; sc, salivary canal; sg, salivary gland (one gland on each side); sp, salivary pump. c lateral view