Pratylenchus fallax
Seinhorst, J.W. 1968
10 females:  L = 0.42-0.56mm; a = 24-33; b = 5.2-6.7; c = 18-24; V = 77-81; stylet = 16-17u.
10 males:  L = 0.40-0.50mm; a = 26-33; b = 5.0-6.2; c = 16-25; stylet = 15u; spicules = 14-16u.
Female (holotype):  L = 0.52mm; a = 29; b = 6.2; c = 18; V = 33803; stylet = 17u.
Lip region with three often rather flat and obscure annules.  Lateral field with four parallel lines and usually some additional lines running obliquely between the inner two.  Only outer two lines proceed past phasmids.  Lateral field sometimes areolated posterior to phasmid.  Tail conical with 16-26 rather narrow annules (Table III), tip rounded or of slightly irregular shape, distinctly crenate to almost smooth.  Phasmids at 9th to 13th annule from tip.

Table III
Frequencies of different numbers of annules on female tails in the type and other populations of P. fallax.

No. of annules 16 17 18 19 20 21 22 23 24 25 26 Total
No. of specimens type pop. 2 4 2 4 12 15 5 1 1 58
No. of specimens five other populations
11 12
No. of specimens total
23 20 23

 Cephalic framework with thin posterior edges extending about two body annules into body.  Stylet with anteriorly flattened or forward-pointing knobs.  Dorsal oesophageal gland opening 2 or 3u behind spear knobs.  Excretory pore at or posterior to level of nerve ring.
 Ovary outstretched, oocytes in single file except for a short region near anterior end.  Spermatheca round, sometimes empty and then narrower and longer.  Distance between vulva and spermatheca 42% to 71% of that between vulva and anus.  Length of postvulvar uterine branch about one-fourth to one-third of distance between vulva and anus; posterior part often consisting of two or three rudimentary elements.
 Male (allotype):  L = 0.46mm; a = 27; b = 6.2; c = 21; T = 32; stylet = 15u; spicules = 15u.
 Testes with double row of spermatocytes.  There is about one male per 5 females.
 Holotype:  female, collected by J.W. Seinhorst, March 1965, slide no. TC 9/1 I.P.O. Nematode Collection, Wageningen.
 Allotype:  male, same data as holotype, slide no. TC 9/2, I.P.O. Nematode Collection, Wageningen.
 Paratypes:  41 females and 15 males, same data as holotype, slides TC 9/3-9/10 I.P.O. Nematode Collection, Wageningen and one slide with females and males in each of the following places, Plantenziektenkundige Dienst, Wageningen; Rothamsted Experimental Station, Harpenden, Herts, England; Plant Industry Station, Beltsville, Md., U.S.A. and Nematology Department, University of California, Davis, Cal., U.S.A.

 Type locality:  apple orchard near Doornenburg, The Netherlands.
 Type habitat:  apple orchard with grass undergrowth on loam soil.

P. fallax is most closely related to P. penetrans, from which it differs only in having a crenate tail tip.  The species differs from P. convallariae in having more and narrower annules on the tail (generally fewer than 20 in P. convallariae), in being smaller and in the lower ratio of males to females (almost 1:1 in P. convallariae).  Females with an empty spermatheca can be distinguished from P. crenatus by the shorter postvulvar uterine sac (length 25% to 35% of the distance between vulva and anus, against almost 50% of this distance in P. crenatus).
 P. fallax is distinguished from P. pratensis by the round spermatheca, which is placed more posteriorly than in P. pratensis.  Moreover, P. fallax is less slender than P. pratensis.  It is easily distinguished from P. irregularis Loof (1960) by the shape of the tail tip and differs from P. cerealis Khak, 1966, in the more posterior position of the excretory pore, the tail not being particularly short and the lip annules being rather flat and obscure.
 P. fallax is widespread in the Netherlands.  It occurs especially in meadows and orchards on loam and sandy loam soils and in places with a more or less natural vegetation.  It is rare in arable land on sandy soils.  Unlike P. penetrans the species most probably is indigenous to the country.  It has probably not been reported before because it was confused with P. penetrans, P. crenatus and perhaps occasionally P. pratensis.  The species was also found in samples from Rochefort, France; Naples, Italy and in England, being the unnamed species of Pitcher, Way & Savory (1966) and of Corbett & Webb (1967).

Photo Gallery- Nine-mile Prairie