DIOSTBACUS. 121 



hypopygium .short, stout, rather disengaged ; its outer appendages 

 are small lamella?. 



The genus Diostracus is so peculiar that more detailed state- 

 ments are unnecessary to distinguish it from other genera. Its 

 most striking character is the peculiar disk-like form of the palpi 

 and their very considerable enlargement in the males. 



The name of the genus (from fii'j, twice, oarpaxov, potsherd) has 

 reference to this character. 



1. D. prasinus LOEW. $ and J . Prasinus, subopacus, abdomine 

 nigricante, pedibus flavis, maris tertio tarsorum anticorum articulo com- 

 presso et in margine supero pilis nigris barbato. 



Leek-green, somewhat dull, with a blackish abdomen and yellow feet ; 

 third joint of the fore tarsi of the male compressed and bearded on the 

 upper margin with long hairs. Long. corp. 0.18 0.20. Long. al. 0.23 

 0.24. 



SYN. Diostracus prasinus LOEW, Neue Beitr. VIII, 44, 1. 



Male. Face for a male very broad, metallic-green or blue- 

 green, sometimes copper-colored, with a rather distinct transverse 

 swelling, and by far not reaching the lower margin of the eyes ; 

 dusted with grayish-yellow. Palpi of unusual size, rather rounded, 

 loosely recumbent upon the proboscis, yellow, covered on the upper 

 side with a thick snow-white powder, and with a delicate, almost 

 imperceptible, white pubescence. Proboscis for a male unusually 

 large and stout, brown. The small antenna? brownish-yellow, 

 most of the third joint brown, the dorsal arista blackish-brown, 

 long and not very strong, with a short, but distinct pubescence. 

 Front above broader, metallic-green or blue-green, seen obliquely, 

 somewhat darker, without dust. Cilia of the upper orbit black, 

 of the lateral and inferior orbits yellow. Upper side of the thorax 

 of a saturate leek-green or parrot-green coloring and with very 

 little lustre ; on its anterior margin there is some gray-whitish 

 pollen, which is interrupted by 'the anterior end of a not very 

 striking and not far-reaching dark-colored middle stripe. The 

 usual black bristles on the upper side of the thorax are few and 

 short ; there are no hairs upon it. If examined from behind, a stripe- 

 like dark scarlet-brown spot, immediately above the root of the wing, 

 may be noticed ; on the posterior margin of the thorax there is also 

 a more distinct covering of brown-grayish dust. Scutellum with the 

 usual bristles, otherwise bare, somewhat short, usually of a more 



