1012 Charles Paul Alexander 



The largo, fleshy larvae occur beneath or among drift at or near the 

 margins of streams. They are usually abundant under saturated decay- 

 ing leaves or under tussocks of grass at the edge of the water. They 

 are entirely herbivorous, feeding on diatoms, decaying plant tissues, 

 and other vegetable matter. The larvae are readily distinguished from 

 all other species of the genus by the small spiracles and the bifid or split 

 lobes surrounding the spiracular disk. Pupation takes place in the mud 

 or earth at the water's edge. Malloch's Tipula sp. 2 (1915-17 b: 200- 

 201) seems to refer to T. abdominalis, but the mouth parts of his speci- 

 mens do not seem to be normal. 



Larva. — Length, 55-65 mm. 



Diameter, 7.5-10 mm. 



Coloration pale grayish brown; anterior end darker. 



Form stout, terete, thin-skinned. Posterior ring of abdominal segment, both above and 

 below, with a naked transverse welt, which bears the setae; this welt very protuberant at 

 its lateral ends, almost like a pair of prolegs. Skin naked, except for a microscopic dotting 

 and the rather short, delicate setae. Chaetotaxy as follows: tergites, on welt at about mid- 

 length, a transverse row of eight setae, the middle pair of each half closely approximated; 

 pleurites with a single seta opposite basal ring, and two opposite posterior ring, arranged 

 one behind the other; sternites with four pairs of setae on welts, anterior middle pair closer 

 together than posterior lateral pair. Spiracular disk (Plate XCVII, 537) moderately large, 

 flattened, truncated, surrounded by six deeply bifid and irregular lobes; ventral lobes elon- 

 gate, with a blunt basal branch bearing two setae; posterior branch longer, indistinctly 

 bifid at tip and with a few setae and several hairs; lateral lobes deeply bifid, the ventral 

 one armed with lateral setae; dorsal lobes small, simple; inner faces of dorsal and lateral 

 lobes with a narrow dark brown stripe, ventral lobes with two narrow, usually indistinct 

 lines, these markings broadest and darkest on dorsal lobes. Spiracles very small, circular, 

 separated by a distance about equal to fouf times diameter of one. Anal gills six, long and 

 slender, the middle one on either side a little shorter than the others. Pleural region of 

 penultimate segment of body with a blunt setiferous tubercle. 



Head capsule and mouth parts about as in genus. Mentum (Plate XCVII, 536) broadly 

 transverse, anterior margin with seven to nine teeth, in the latter case the outermost teeth 

 very indistinctly separated from the sublateral teeth. Hypopharynx broad, anterior margin 

 with teeth very indistinct. 



Pupa. — Length of cast pupal skin, about 35 mm. 



Pronotal breathing horns short, straight, cylindrical; apex short, and but little if at all 

 expanded. Details of mouth parts as in other species of genus. Wing sheaths ending 

 before apex of second abdominal segment. Leg sheaths extending to about opposite end 

 of third abdominal segment; fore tarsi the shortest, hind tarsi the longest, ends of tarsal 

 sheath thus forming a broad, inverted U-shaped notch. 



Abdominal armature generally weak. Tergites (Plate XCVII, 538) with subterminal row 

 broken, consisting of an anterior median pair of large spines, laterad of which are two or 



