6G ASCAROIDEA 



Cobb, 1913; Tijlenchorhynchus Cobb, 1913; Dolichodorus 

 Cobb, 1914; lotonchium Cobb, 1920; Aphelenchulus Cobb, 

 1920 ; Parasitylenclius Micoletzky, 1922 ; Paratylenchus 

 Micoletzky, 1922 ; Chitinotylenchus Micoletzky, 1922. 



Cuticle striated, without bristles. Lateral alae often present. 

 Head usua,lly not distinct, usually without lips, papiUae or 

 bristles. Lateral organs unknown. Stylet consists of three 

 rods fused throughout, with distinct knobs posteriorly. Caudal 

 end of male usually with alae. One or two accessory pieces 

 generally present. Testis single. Female genital tubes 

 paired, opposed ; the posterior may be rudimentary and 

 without ovary. Caudal glands and spinneret absent. 



Hab. Chiefly soil, especially on roots of plants. Some 

 species occur in fresh water or decaying substances, or even 

 in the sea. Many are plant-parasites, a few parasites or semi- 

 parasites of insects. 



Genotype : A. ['Vibrio'\ tritici (Steinbuch, 1799) (by page 

 precedence). 



Gervais & van Beneden, 1859, Zoologie Medicale, Paris, ii, 

 101; Bastian, 1865, Trans. Linn. Soc. London, xxv (2), 125; 

 Micoletzky, 1922, Arch. f. Naturg., Abt. A, Ixxxvii, 542. 



Micoletzky (1922) proposes to divide Tylenchus into two 

 subgenera, Tylenchus s.s. and Chitinotylenchus. The latter 

 apparently has as its type T. paragracilis Micoletzky, 1922, 

 and is characterized by the presence, on the anterior end of 

 the body, of a more or less complex chitinoid investment. 

 The value of this distinction appearing somewhat doubtful, 

 we prefer to regard Chitinotylenchus, for the present, as a 

 synonym. A number of other names included in the synonymy 

 have been proposed for forms which apparently differ only in 

 unimportant details from the type of Anguillulina. Para- 

 tylenchus was based on a single female specimen. Parasity- 

 lenchus was proposed for the reception of two species which 

 are said to have a free-living generation and a generation 

 parasitic in beetles. These forms have, in the free-living 

 generation, a poorly-developed median oesophageal bulb, and 

 the caudal alae of the male are slight or absent. Considered as 

 generic differences from Anguillulina these characters are very 

 indefinite, and we have therefore treated Parasitylenchus as a 

 S3rnonym. 



2. Tylenchulus Cobb, 1913. 



In most respects this genus agrees with Anguillulina,* from 

 which it is said to differ in the following characters : (1) There 



* In some respects, and especially in the swelling of the body of the 

 female, Tylenchulus seems even more closely related to Heierodera (see 

 below, p. 67). From this genus, however, it differs in having only a 

 single female genital tube, in the absence of an anus, and in the fact 

 that the vulva is not quite terminal. 



