116 ILLINOIS BIOLOGICAL MONOGRAPHS [326 



GREGARINA NIGRA Watson 



[Figures 210, 333, 334, 335] 



1915 Gregarina nigra Watson 1915 :33 



Hosts: Melanoplus femur-rubrum (deGeer) ; Encoptolophus 

 sordidus (Burm.). 



This parasite seems to be present only as a secondary one. It never 

 occurs in large numbers but is generally found in the same host as Grega- 

 rina rigida. During the season of 1913, I found the parasite compara- 

 tively frequently, but not over half a dozen Acridiidae yielded the species 

 when collections were made in the fall of 1914. It is easily differentiated 

 from the more commonly found species in both color and shape, especially 

 of the protomerite. It was collected only at Urbana, Illinois. 



The maximum length of an association found was 1 mm. The ratios 

 of various parts of the body are about the same as for G. rigida. The 

 shape of the body is, however, quite different. The protomerite is shaped 

 like a truncated cone ; it is widest at the base, flattened on the top and 

 square cornered. It is approximately as high as wide at the base ; there 

 is no constriction or only a very slight one at the septum. A slight in- 

 dentation persists at the apex of the protomerite left by the detachment 

 of the knob-like epimerite. The deutomerite is cylindrical, of the same 

 width throughout and very little wider than the protomerite. It termi- 

 nates in a broadly rounded extremity. The protomerite of the satellite 

 is often not at all flattened but is little shorter than that of the primite 

 and of approximately the same shape. 



The endocyte of the deutomerite is very opaque and dense, being 

 black in transmitted light. The protomerite is somewhat less dense than 

 the deutomerite. The nucleus is not visible in vivo. It is spherical, in 

 diameter about one third the width of the deutomerite and contains many 

 karyosomes. The epicyte is thick at the anterior end of the protomerite, 

 being thin elsewhere. 



I have not been able to differentiate the cysts of this species (if pres- 

 ent in my collections) from those of G. rigida. The size would be about 

 the same, judging from the size of the associations. I have never seen an 

 infection in which this species alone was present so have no way of know- 

 ing exactly which species yielded the cysts found when both species are 

 present in an infection. In the instance of every cyst from Acridiidae 

 which I have watched develop, spore ducts grew from small orange col- 

 ored discs on the surface. The spore ducts were always short and the 

 spores doliform. 



