OF WASHINGTON, VOLUME XVII, 1915 117 



by a very shallow impression; ocellar basin triangular, open below; facial 

 quadrangle wider than high; pronotum subopaque with sparse tubercles; 

 mesonotum similarly scupltured; mesepisternum and sternum shining, 

 under high magnification, very finely reticulate; tibiae and tarsi with weak 

 short spines; abdomen shining; sheath nearly parallel-sided, obtusely 

 rounded apically. Black; mandibles and palpi piceous; inner orbits 

 below antennae, posterior orbits behind the eye, posterior margin of the 

 pronotum laterally and tergites 2 to 8 on lateral posterior margin, greenish 

 white; legs beyond the coxae rufo-testaceous; wings hyaline, slightly milky; 

 venation pale brown anteriorly, pallid posteriorly. 



Rose Camp, California. Described from two females recorded 

 under Bureau of Entomology, No. Hopk. U. S. 4996a which re- 

 fers to a note stating that these specimens were reared from larvae 

 and pupae collected in the cells near the outer surface of the wood 

 of a large incense cedar (Libccedrus decurrens Torr.). Material 

 collected August 8, 1913, and reared June 22, 1914, by H. E. 

 Burke. 



Type: Cat. No. 19162, U. S. N. M. 



Two poorly preserved larva? are available for study but they 

 are not in good enough condition to satisfactorily describe. How- 

 ever, as they appear to lack the cerci which occur on the apical 

 sternite below the anal orifice, and have the antennae more like 

 the Xiphydriidae it is probable that they are more like the larvae 

 of the Xiphydriidte than the Cephidae. 



GOMMENSALISM IN DESMOMETOPA. 



(Diptera; Agromyzidcc.) 

 BY FREDERICK KNAB, Bureau of Entomology. 



The small flies of the genus Desmometopa have been repeatedly 

 observed under circumstances which indicate a remarkable special- 

 ization in habits. There are now on record a series of observations, 

 made independently in widely separated parts of the globe, 

 which all show that these flies feed upon the juices of freshly killed 

 insects; however, unable to themselves kill their prey, they de- 

 pend upon various rapacious arthropods, with whom they appcnr 

 to live in more or less close association. 



The Hungarian naturalist Ludwig Biro is responsible for the 

 first and at the same time most remarkable observation in this 

 connection. He observed a species, Desmometopa minutissima, 1 



1 Described as an Agromyza by Van drr \Yulp and so recorded by Banks 

 (Entom. News, xxii, 196; 1911). Mik, in the article quoted in the following, 

 has referred the species to its proper genus. 



