ENTOMOPHTHOREAE OF THE UNITED STATES. 155 



Empiisao in aphides and flies, the one class of hosts usually having a sweet secretion 

 and the other pi-eferi-ing sweet substances as food, thus supplying a nutritive medium 

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

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

 the Em'imsa 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 enumci-ation, for example, the two forms included under Trvplosporium can 

 hai-dly be pi'operly placed either at the beginning or at the end of the remaining series, 

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

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

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

 remaining species found in Europe and not yet distinguished in this country, with l)rief 

 characters and references, is appended foi-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., refei-, as in the previous pages, to the appended list of papers consulted where full 

 titles and refei-ences are o'iven. 



O' 



Empusa Coim, i855. 



Empusa Muscae Colin. 

 PI. 14, figs. 1-9. 



Empusa Muscae, Colin I. c. A. Bi-efeld Z. c. A; I. c. B, p. 28; I. c. C. Schroeter I. c, 



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

 Entomophthora Muscae, Fresenius I. c. A, p. 883 ; I. c. B, p. 202, figs. 1-2.3. Giard I. c. 



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

 3Ti/iophi/to7i Cohnii, Lebert l. c. 

 ?Spore)Hlonem.a 3Itiscae, Fi'ies I. c. 



Gonidia bell-shaped or nearly s[)herieal, 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. Conidiophores 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. Besting spores, azygospores, produced laterally oi- ter- 

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

 Host attached to substratum by proboscis. 



Hosts. Diptera: Masca domestica, Lucilia Caesar, Ccdliphora vomitoria and other 

 large flies; also Syrphidae of several genera. 



Habitat. United States, Europe, South America. 



Tills familiar Empusa is as common as it is widely distributed, and is at jiresent the 

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



