THE INTESTINAL FLAGELLATES OF INSECTS 249 



Patton, 1908, in reality a trypanosome of cattle in its insect host? 

 The flagellates definitely known to be trypanosomes, herpet- 

 omonads of the latex of plants or leishmanias will not be discussed 

 further in this chapter, since they are involved either directly or 

 indirectly in subjects treated in other chapters. 



In the third group we recognize the members of the same family 

 (trypanosomid^) which, while they retain definite biological, 

 structural, and phylogenetic relationships with the trypanosomes, 

 phytomonads, and leishmanias, are, nevertheless, exclusively insect 

 parasites with no definitive vertebrate or plant host. 



To a fourth group we may consign all gut flagellates of insects 

 belonging to families other than the trypanosomid^ — not such a 

 motley assortment if we remember that their affiliations are strictly 

 with genera which are preeminently intestinal flagellates of a wide 

 variety of higher animals. The scope of the remaining portion of 

 the chapter will be limited to these last two groups of gut flagel- 

 lates of insects. 



TRYPANOSOMID^ OF INSECTS 



The TRYPANOSOMiD^ of insccts under consideration here com- 

 prise the now generally recognized genera Leptomonas, Herpet- 

 omonas, and C^'ithidia. These flagellates are primarily gut dwellers, 

 although in certain cases other cavities and tissues of the insect's 

 body are found to be occupied by them. In such cases the primary 

 site of infection is the intestine. The number of described species 

 is not only large, but constantly increasing. 



One of the outstanding (not to say long-standing) problems is 

 in connection with the validity of the generic names Leptomonas 

 and Herpetomonas. Both were established by Kent (1880-1882) 

 in the same volume. Leptomonas butschlii, a flagellate found by 

 Biitschli in the nematode, Trilobus gracilis, is the type of its genus. 

 Herpetomonas muscce-domesticce, first observed by Burnett, is 

 made the type of another genus. The former name has priority by 

 two pages over the latter, and according to the rules should be 

 retained if the two species can be shown to be cogeneric. A re- 

 investigation of the flagellate of the nematode is needed in order 

 that we may know if its structure and life-history place it defi- 

 nitely in the same genus with the herpetomonads of insects. 

 Biitschli's original paper described and figured a contractile vacuole 

 in the anterior region of his flagellate, a cell structure unknown 



