14 



BULLETIN 1218, U. S. DEPARTMENT OF AGRICULTURE. 



to be longer and slightly less opaque than those on the abdominal segments. 

 In front and at each end of the anal aperture are numerous spines. On the 

 front half of each segment are scattered bristles. On each side of the mid- 

 ventral line of each thoracic segment is a small tuft of 3 to 4 bristles varying in 

 length. Dry mounts are the most satisfactory for studying these skins. 



SECOND INSTAR. 



Soon after the first molt of T. punctifer, the larva (fig. 10, &) is 2.7 to 3 

 millimeters long; the general color is creamy white; preserved in alcohol it 

 becomes a pale yellow. The segmentation is the same as in the first instar. 

 As in the full-grown larva, the head capsule telescopes into the two front 

 thoracic segments. Each abdominal segment has a strip of yellow pile around 

 both the anterior and posterior margins. The second and third thoracic seg- 

 ments have the yellow pile on only the anterior margins. The first thoracic 

 segment into which the head capsule telescopes has yellow pile over the anterior 

 and extending back over nearly half the segment. Each of the seven abdominal 

 segments on its anterior margin has 6 tubercles, 3 in a line each side of mid- 

 venter about equally spaced, the outer one being slightly below the midlateral 

 line. The tubercle nearest the midventral line is circular, the outer two being 

 oval. The tubercles are beset with stout spines and aid in locomotion. On the 

 venter of each thoracic segment about midway are two tufts of 3 or 4 bristles 

 like those described on the exuvium of the first instar. All the segments have 



numerous scattered bristles on 

 the anterior half. 



The anus is elliptical in 

 shape, with long axis trans- 

 verse. It has a margin of 

 yellow pile which extends in a 

 triangular area to near the 

 midlateral line. 



The siphon, slightly shorter 

 than the anal segment into 

 which it telescopes, is tubular 

 and of constant diameter for 

 two-thirds of its length. The 

 posterior third narrows slightly 

 to its circular end. The an- 

 terior end of the siphon has a 

 wide margin of yellow pile. 

 Where the tube narrows are 

 four pairs of bristles, one pair on each side ventrally and one pair on each side 

 dorsally. Several bristles are seen near the end around the opening. 



In the anterior part of the anal segment above the anus Graber's organ 

 (5) appears as two pairs of dark-colored globules. The anterior pair is the 

 larger. They are dark brown and opaque. This observation was facilitated 

 by using specimens cleared in hot five per cent caustic potash for 45 minutes. 

 For study best results were obtained from alcoholic mounts. It was found very 

 difficult to mount the specimens in balsam without great distortion. 



DESCRIPTION OF MATURE LARVA. 3 



(Figs. 11-13; PI. I, D) 



Larva (mature) about 47 millimeters long, 5 millimeters wide; subcylin- 

 drical, elongate, tapering anteriorly and posteriorly ; head well, developed ; 

 thoracic segments 3 ; abdominal segments 8 ; two swollen, rounded anal lobes 

 located ventrally on eighth abdominal segment, on each side of a longitudinal, 

 almost vertical, anal slit (fig. 11). 



Head. — Head (fig. 13) porrect, deeply retracted with about four-fifths 

 of head capsule invaginated, entire head capable of complete withdrawal into 

 thorax. Length of head capsule about 4.5 millimeters; width about 1 milli- 

 meter ; sides parallel. Head capsule smoothly chitinized ; ground color pale 

 yellowish. Dorsal surface of capsule with long and rather broad, anteriorly 

 and posteriorly attenuate, dark brown stripe on each side of epicranial suture ; 

 this stripe is accompanied, posteriorly and exteriorly, by a much shorter but 

 almost as broad, spindle-shaped, dark-brown spot, and also medianly and 



Fig. 10. — a, Egg of Tabanus punctifer ; b, larva of 

 T. -punctifer after first molt. Greatly enlarged. 



3 By Adam G. Boving, Bureau of Entomology. 



