34 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 68 



Arrenopus americanus was loaned from the Vienna Museum for exami- 

 nation and the synonymy of Coquillett verified. Townsend's types 

 for argent if rons and cineracens have been loaned by the University 

 of Kansas Museum, and the synonymy of Coquillett and of Aldrich 

 verified. 



In the four specimens in which the female reproductive organs were 

 dissected there was agreement in the following characters (pi. 4, fig. 20) : 

 Spermatheca, three, their ducts elongate, without inflations, two of the 

 ducts united on the distal half; accessory glands of equal size, some- 

 what less than ten times as long as their ducts; uterine pouch dis- 

 tinctly chordate; ovaries emptied, even before maggots in uterus had 

 reached their full de\^elopment. 



The only difference in the morphology of the uterine maggot noted 

 between this species and others of the genus studied, is found in the 

 buccopharyngeal apparatus (pi. 5, fig. 31). In this, the median hook 

 is suddenly constricted just beyond the base, expanding again near 

 the tip, thence tapering to a stout point, the axis of which is almost 

 perpendicular to the axis of the buccopharyngeal apparatus; lateral 

 hooks with broad, nearly parallel sides to near tips, thence tapering 

 abruptly to minute recurved points having a deep U-shaped invagina- 

 tion on ventral margin. 



The puparium very closely resembles that of vigilans and ruhriven- 

 tris, from which, however, it differs in minor characters. It is 

 chestnut brown in color, with minute spines encircling the anterior 

 part of the thoracic segments; each segment with fine lateral stria- 

 tions, the anal segment without well defined spines above the de- 

 pression. In lateral view, it is deepest at the middle, tapering 

 slightly in both directions; the dorsal margin is straight, the ventral 

 margin broadly convex. Anterior spiracle with six to seven papillae; 

 posterior spiracles separated by a distance slightly greater than their 

 width, and located slightly above the horizontal bisecting plane. 

 Anal depression shallow. 



The kno^vn range of trilineata is greater than that of any other 

 species of the genus. Northward it has been recorded as far as New 

 Hampshire, Ontario, Illinois, Minnesota, Canadian Northwest 

 Territory, and British Columbia. Curran reports it from Fort Simp- 

 son, near 62° latitude, far north of the known distribution of any 

 other species of this group, and not far from the Arctic Circle. South- 

 ward from this limit it has been reported from numerous localities 

 representing nearly every state of the United States, and from Mexico, 

 Nicaragua, and Costa Rica. Townsend has recovered what is in all 

 probability the same species from Peru. It is not known outside of 

 the American continents. 



Notwithstanding its abundance and wide distribution, but very 

 little has been published on the biology of this species. The writer 



