68 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.40. 



all tibiae, and all tarsi dark brown; antennae black; wing veins and 

 stigma pale brownish. 



Habitat. — Havana, Illinois. 



Four specimens bearing Illinois State Laboratory of Natural His- 

 tory, No. 13068. According to Mr, C. A. Hart these specimens were 

 taken by him September 23, 1894, on the shore of Quiver Lake, near 

 Havana, Illinois, where they were found running about on the surface 

 of duckweed {Lemna). 



Genus GNAMPTODON Haliday. 



This genus is like Opius, except that the second abscissa of radius 

 is scarcely longer than the first abscissa, the second cubital cell very 

 short, and the abdomen is quite different, the suture between the 

 second and third tergites being deep, foveolate, and strongly arched, 

 while the third tergite has an oblique furrow from the anterior middle 

 to the lateral margins. The second tergite has a transverse, smooth, 

 slightly raised area at base. 



GNAMPTODON NEPTICULAE Rohwer. 



Plate 34, fig. 1; plate 35, fig. 13. 

 Gnamptodon nepticulae Rohwee, Proc. U. S. Nat. Mus., vol. 49, 1915, p. 229. 



Halitat. — Virginia. 



Host. — Nepticula castaneaefolieUa. 



Genus OPIUS Wesmael. 



The genus is sufficiently characterized in the description of the 

 subfamily and the generic key. As here constituted the genus 

 includes the vast majority of the American species of Opiinae. 



Key to the species of Opius. 



1. Second abscissa of radius shorter or scarcely longer than the first cubital cross 



vein 2. 



Second abscissa of radius longer than the first cubital cross vein 11. 



2. Mesopleiu*ae striate, the striae arcuately curAdng from the superior to the posterior 



margin ; abdominal tergites wrinkled secundus Viereck. 



Mesopleurae not striate; abdominal tergites not all wrinkled 3. 



3. Dorsum of the mesothorax granularly sculptured; first transverse cubitus nearly 



obsolete; parapsidal grooves impressed and terminating posteriorly in a striate 

 area; first and second abdominal tergites and basal border of the tliird striate. 



appalachicolus Viereck' 



Dorsum of the mesothorax smooth; first transverse cubitus distinct; parapsidal 



grooves incomplete and rarely terminating in a striate area; first and second 



tergites sometimes striate. 4. 



4. Malar space longer than the mdth of a mandible at base 5. 



Malar space shorter than the width of a mandible at base 10. 



5. Posterior wing with a distinct postnervellus;' ovipositor strongly exserted 6. 



Posterior wing without a distinct postnervellus; ovipositor short 8. 



1 The name postnervellus is applied to a crossvein or stub of a vein, interstitial -with the basal nervure 

 in the posterior wing, and extending backward toward the posterior margin of the wing, parallel with 

 the nervellus. 



