38. 



Genus Heterodera Schmidt, I87I 

 (Key to the species prepared by A.L. Taylor) 



Notes This key is designed to facilitate identification of the species 

 of Heterodera, using only characters of the mature cysts and their con- 

 tents, that is, eggs with second stage larvae. Certain characters used 

 in the key msy not be visible on other than fully mature cyets. 



1. Body of cyst ovoid to globular, that is with posterior portion 

 rounded and vulva not located on a distinct protuberance (figs, 1 



and 2) Heterodera rostochiensis group #U 



2. Basic element of pattern of outer layer of cyst wall at middle portion 

 of cyst short zig-zag lines with little or no trace of regular trans- 

 verse arrangement (figs. 7 and 8) sometimes modified to appear as net- 

 work (fig. 12) 3 



Basic element of pattern at outer layer of cyst wall at middle portion 

 of cyst straight or wavy lines (figs. lU and I6) lines at right angles 

 to axis of cystj sometimes broken by short oblique or vertical lines 

 outer layer of cyst may have grainy appearance (fig. 18) 



• Heterodera cacti group 7 



3. Mature cysts with dark bodies (brown knobs) and often sheaf-shaped 

 object (lining of vagina) at posterior end (fig. ll). On immature 



cysts, these seldom visible, and then do not appear dark. • 



Heterodera schachtii group 8 



Mature cysts without brovm knobs or sheaf-shaped object at posterior 

 end • Heterodera gottingiana group 11 



h» H. rostochiensis group . Cyst often ovoid, anus located at a transpar- 

 ent spot on cyst so that anal and vulvar openings appear to be about 

 the same size when seen by transmitted light (fig. 2l). Hyaline por- 

 tion of larval tail much longer than stylet ... . Heterodera punctata 

 Cyst ovoid to globularj anal opening appears much smaller than vulva 

 opening (figs. 19 and 20). Hyaline portion of larval tail about the 

 same length as stylet 5 



5. Larvae very slenderj length about 39 times greatest widthj orifice of 

 dorsal oesophageal gland about two-ttiirds stylet length posterior to 



stylet knobs. Heterodera leptonepia 



Length of larvae about 22 times greatest width; orifice of dorsal 

 oesophageal gland about one-fourth stylet length posterior to stylet 

 6 



6. Distance between vulva and anus about one and one-half tiraes diameter 



of vulva Heterodera rostochiensis 



Distance between anus and vulva about two and one-half times diameter 

 of vulva Heterodera tabacum 



7» H. cacti group. Hyaline portion of larval tail about as long as styletj 



stylet knobs concave anteriorly Heterodera weissi 



Hyaline portion of larvae of larval tail usually stiorter than stylet; 

 stylet knobs convex anteriorly Heterodera cacti 



