cobb: notes on mononchus and tylenchulus 



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HELMINTHOLOGY. — Notes on Mononchus and Tylenchulus. 

 N. A. Cobb. Bureau of Plant Industry. 



Mononchus. Various observers have suggested that species of 

 the genus Mononchus may be injurious to vegetation. For some 

 years the writer has accumulated observations showing the species 

 of this genus to be carnivorous. On various occasions the intes- 

 tine has been seen to contain other nematodes that have been 

 swallowed whole. On one occasion a Mononchus was captured 

 in the act of swallowing another nematode. When Mononchi are 

 placed in water with other species of nematodes the latter are 

 sometimes seen suddenly to exhibit active motion, apparently 



Fig. 1. Seven females of Tylenchulus semi-penetrans in various stages, as 

 found on a feeding root of orange tree. The two outside specimens are younger 

 than the others, which are adult or nearly so. A considerable portion of the 

 head end of the worm is inside the root. The roots are injured, a, tail end; 

 b, vulva; c, excretory pore; d, immature egg; e, ripe egg. 



expressive of fear, when touched by the head of one of the Mon- 

 onchi — acting, in fact, as if suddenly nipped or bitten. It 

 would appear that Mononchi are beneficial to vegetation, rather 

 than injurious, as the nematodes they feed upon are often 

 injurious species. 



Tylenchulus (New genus). Mr. E. E. Thomas has recently 

 announced in Circular No. 85 of the California College of Agri- 

 culture a very interesting discovery in connection with the roots 

 of citrus trees. Mr. J. R. Hodges, California State Horticultural 

 Inspector, observed nematodes from the roots of orange trees, and 

 concluded they were injurious. Thomas' investigations showed the 

 nematodes to be of common occurrence, but he nevertheless con- 

 cluded that the species was one not hitherto found on citrus 



