J30CS.S.432) 



THE MONONCHS 



ing of all, on other nemas and has made it practically certain that all 

 mononchs are predaceous. 



Economic Importance. If, as is often the case, the nemas destroyed 

 by the mononchs are nemas injurious to agriculture, then the mononchs 

 are beneficial to man. The first definite instance of this kind was reported 

 in the Journal of Agricultural Research in September, 1914 : Mononchus 

 papUlatus was shown to feed upon Tylenchulus semipenetrans, the latter 

 a nema infesting the roots of citrus trees. Since that time the writer has 

 observed many similar instances, fourteen of which are recorded herein. 

 Formerly mononchs were considered harmful to vegetation. The 

 basis of this opinion was twofold: first, they were known to congregate 

 about the roots and between the leaf sheaths of plants, especially succu- 

 lent plants, in sufficient number to justify the opinion that they would be 

 harmful, provided they were vegetarians; second, vegetable matter was 

 often found in their intestines. 



More careful investigation, however, has disclosed other facts incom- 

 patible with this opinion that mononchs are harmful to vegetation. The 

 food-habits of mononchs have now been more carefully investigated, as 

 herein recorded, and each species so studied has proved to be carnivorous. 

 The presence of vegetable matter in a mononch's intestine proves to be no 

 very definite criterion of its food habits, appearances to the contrary not- 

 withstanding. A deception has arisen that 

 is now easily explained. The occurrence of 

 vegetable organisms in the intestine of a 

 mononch is merely incidental ; in many in- 

 stances it would be impossible for the mon- 

 onch to devour its prey without at the same 

 time swallowing vegetable matter. For in- 

 stance, suppose a mononch to bolt, as one 

 of its victims, a monhystera a common 

 occurrence. Monhysteras are vegetarians, 

 some of them feeding almost exclusively 

 upon diatoms, others upon other kinds of 

 unicellular algae. Both on account of their 

 peculiar structure and their bright green 

 color, these diatoms and other algae are very 

 conspicuous objects in the intestine of the 

 monhystera. Imagine now the appearances 

 presented by the body of an ingested mon- 

 hystera, swallowed whole, or nearly so, and 

 lying lengthwise in the intestine of a mononch. Under such circum- 

 stances, which are entirely normal, the diatoms and other algae in the 

 intestine of the monhystera may be observed through the colorless tissues 



FIG. 1 

 A mononch 

 about to seize 

 its victim. 

 The head is 

 drawn from 

 nature and 

 is exact in 

 every detail. 

 The body is 

 more or less 

 posed. The 

 strong teeth 

 and rasp-like 

 organs in the 

 mouth are 

 well shown. 



