Eggs of Tylenchorhynchus agri Ferris were deposited as a single cell and the embryogeny was similar to that of other Tylenchorhynchus Cobb species. At 27C, hatching of eggs occurred 7 days after oviposition and the second-, third- and fourth-stage juveniles and adults were formed at 7, 13, 19 and 25 days, respectively, after oviposition. Nematodes fed ectoparasitically on red clover (Trifolium pratense L.) and bluegrass (Poa pratensis L.), with only the stylet tip inserted in epidermal cells of the root-hair zone. Duration of feeding was usually less than 5 min.