ENTOMOPIITIIOHKAK OF THE UNITED STATES. 



155 



Empusac in aphides and flics, the one class of hosts usually haying a sweet secretion 

 and the other preferring sweet substances as food; thus supplying a nutritive medium 

 for the growth of yeasts in connection with the Empusa. It has occurred to me that the 

 frequent presence of yeasts in this connection might indicate a sweetish secretion from 

 the Empusa itself in order to attract hosts for infection; but I have seen no indications 

 that this is the fact. 



A natural arrangement of the species of Empusa is a matter of great difficulty, 

 since their characters do not, I think, indicate a single line of development. In the suc- 

 ceeding enumeration, for example, the two forms included under Triplosporinm can 

 hardly he properly placed either at the beginning or at the end of the remaining series, 

 and their position between Empusa proper and Entomoplithora is equally unsatisfactory. 

 The near relations of the forms described as E. Caroliniana and E. Lampyridarum is 

 also a matter of doubt which may perhaps be removed by further study. A list of the 

 remaining species found in Europe and not yet distinguished in this country, with brief 

 characters and references, is appended for the convenience of students and includes, I be- 

 lieve, all published names not previously referred to. References given as I. c, I. c. A, 

 etc., refer, as in the previous pages, to the appended list of papers consulted Avhere full 

 titles and references are given. 



ElVIPUSA Colin, 1855. 



Empusa Muscae Colin. 

 PL 14, figs. 1-9. 



Empusa Muscae, Cohn I. c. A. Brefeld I. c. A; I. c. B, p. 28; I. c. C. Schroeter I. c, 



p. 221. Nowakowski I. c. B, p. 176. 

 Entomophtliora Muscae, Fresenius I. c. A, p. 883; I. c. B, p. 202, figs. 1-23. Giard I. c, 



p. 358. Sorokin I c. C, p. 195, figs. 377, 582-585.' "Winter I c. 

 Myiophyton Cohnii, Lebert I. c. 

 ? Sporendonema Muscae, Fries I. c. 



Conidia bell-shaped or nearly spherical, with a broad subtruncate base and sharply 

 pointed apex; 18 X 20// -25 X 30/,; containing usually a single large oil globule, and 

 surrounded after discharge by a mass of protoplasm. Gonidiophores simple, broad 

 and stout, tapering gradually to a narrow base; emerging in white rings between the 

 segments of the host, without coalescing over its body. Secondary conidia like the 

 primary, or more commonly subovoid, small, rounded at the apex and formed by direct 

 budding from the primary form. Resting spores, azygospores, produced laterally or ter- 

 minally from hyphae within the host; spherical, colorless, 30-50,* in diameter (Winter). 

 Host attached to substratum by proboscis. 



Hosts. Diptera: Muscat domestica, Lucilia Caesar, Callipliora vomitoria and other 

 large flies; also Syrphidae of several genera. 



Habitat. United States, Europe, South America. 



This familiar Empusa is as common as it is widely distributed, and is at present the 

 only species known south of the equator. It is probable that it is as universal as its more 



