LEUCOSTOLA. 151 



differ from them precisely in the same manner as from the species 

 Argyra. 



The name of the genus (from vijfia, the thread, and Ttp^xroj, po- 

 dex) has reference to the thread-like form of the exterior ap- 

 pendages of the hypopygium. The species hitherto known are 

 all European. 



Gen. XXVI. LEUCOSTOLA. 



The species of Leucostola, like those of Argyra, have usually 

 upon the abdomen, and often also upon the thorax, a thick bril- 

 liant silvery dust, which renders them easy to recognize. The 

 first joint of the antennae is entirely hairless, the second is trans- 

 verse, the third bare, rather large in the male ; the apparently 

 bare and distinctly two-jointed arista is very near the tip of the 

 antennae. Wings broad, the posterior angle rather protruding ; 

 the first longitudinal vein is farther from the margin of the wing 

 than in most of the other genera, and is also much longer than 

 usual ; the fourth longitudinal vein is inflected forward before the 

 middle of its last segment, thence, however, again parallel with 

 the third ; the posterior transverse vein is not approximated to the 

 margin of the wing. The first joint of the hind tarsi has no 

 bristles. Hypopygium small, imbedded ; its exterior appendages 

 are two small narrow lamellae, bent downward ; the interior ap- 

 pendages are of rather simple structure, and often not distinctly 

 visible. 



The close relationship of the genus Leucostola to that of Argyra 

 can be easily perceived by a comparison of their characters. There 

 is scarcely any difference between them, but that the first joint of 

 the antennae of Leucostola is entirely without any hair, while in 

 A rgyra it is distinctly covered with hair. 



The name of the genus (from %(vxoi, white, and jto^»}, dress) has 

 reference to the beautiful silvery lustre which covers the abdomen 

 and sometimes also the thorax of most of these species. 



The known species belong in part to Europe and in part to 

 America. 



