FLIES OF THE GENUS OGCODES — SCHLINGER 241 



articulation of the oral hooks. The differences in the formation of 

 this structure appear to be specific among the species which have been 

 figured, such as brunneus (Hutton) by Dumbleton (1940), pallipes 

 Latreille by Millot (1938), and adaptatus, new species, as figured in 

 this work. The chaetotaxy of the known species also appears to be spe- 

 cific. Eachtergite usually has a row of setae along the posterior margin, 

 while each sternite has several rows and various types of setae. The 

 caudal segment bears one large, anterior, dorsal pair of setae, as well 

 as several short setae, hooks, and a sucking disc at the apex. The 

 single pair of spiracles are dorsal, posterior, and are located on a 

 separate sclerite between segments xi and xii. The tracheae are 

 quite straight, one to each spiracle, running nearly into the head 

 segment. They are joined only once, just anterior to the spiracles. 

 For further notes on the larvae see the references cited above. 



Mature or third-instar larva: After the first-instar larva 

 becomes attached inside the host, a period of time passes (varying 

 apparently with the growth rate of the spider which is between 6 and 9 

 months) during which there are two molts. The thu-d-instar larva 

 develops rapidly, consumes most of the host contents, makes an exit 

 hole along the epigastric furrow of the spider and emerges posteriorly. 

 The larva is sticky on the surface and adheres, ventral side up, to the 

 spider webbing, which is made just prior to the emergence of the 

 parasite. 



The third-instar larva is whitish and measures from 5.0 to 12.0 

 mm. in length. It has a small, yellowish white head, a distinct, 

 yellow, barely segmented thorax bearing a pair of pro thoracic spu-acles, 

 and a large abdomen of 9 apparent segments. The precaudal and 

 caudal segments are somewhat restricted, and bear a pair of dorsal 

 spiracles. The larva pupates in 1 to 3 days after emergence. 



Pupa: Pupation occurs outside, but usually quite near the host's 

 body. A distinctly coiled, dark brown to black meconium is passed 

 as the prepupa is formed. The duration of the pupal period varies 

 from 2 to 10 days, during which time the pupa becomes increasingly 

 darker until just before adult emergence, when it is nearly black. 



The pupa (pi. 1, fig. 1) is adult-like, having an obvious head, 

 thorax, and abdomen, the whole of which measures from 4.0 to 10.0 

 mm. in length. The head has a curving row of papilliform protuber- 

 ances on each side. There are pro thoracic spiracles, and spiracles 

 on abdominal segments ii-v (sometimes referred to as i-iv). There 

 are 9 visible abdominal segments, the first and last three of which are 

 not separated into tergites and sternites. The scutellum is an obvious 

 protrusion when viewed laterally. 



Host: Most of the Nearctic hosts are of the family Lycosidae 

 or wolf-spiders. (For a complete host-parasite hst, see table 1.) 



