nematodes and it would not he proper to classify them other- 

 wise. If it happens that they are adaptable to unusual environ- 

 ments it is but an evidence of the nature of the group to which 

 they belong. 



Because of the numerous difficulties and inconsistencies ap- 

 parent in any classification of nematode life histories, each of 

 the authors has followed the system which seemed most logical 

 to himself. Thus, the nematode parasites of invertebrates are 

 grouped according to the manner and site of parasitism, be- 

 ginning with the semiparasitic forms that mature at the death 

 of their host and feed upon the carcass, then taking up the in- 

 testinal parasites and finally the parasites of the body cavity. 

 Most of the invertebrate parasites belong to the Rhabditoidea 

 and Tylenchoidea in which groups parasitism has arisen so 

 many times and adaptations are so numerous that life cycles 

 have little in common with systematics. The vertebrate para- 

 sites are taken up according to their systematic position since 

 the large groups show some consistency within themselves and 

 distinct trends are apparent. 



For those who desire an outline after the manner of Seurat, 

 we have revised his system to include groups with which he did 

 not deal. The classification is entirely artificial. Nematodes 

 are divided into the Vagantia or wanderers and the Parasitica. 

 The Vagantia includes members of the Rhabditoidea, Tylen- 

 choidea, Monhysteriua, Chromadorina, Enoplina and Dorylai- 

 moidea. Some representatives of most, if not all, of these 

 groups have been found in more or less close asspciation as 

 semiparasites or parasites of plants or animals but the groups 

 are basically free living. The only known modification in the 

 life history of such free living forms is the existence of n 

 persistent stage. Thus far, this stage is known only in ter- 

 restrial and semiterrestrial forms. 



The Parasitica is subdivided into Phytoparasitica and Zoo- 

 parasitica. All the known nematode parasites of plants belong 

 to the Tylenchoidea though certain members of the Rhabditoidea 

 and Dorylaimoidea are commonly found in close association 

 with plants. In the Zooparasitica the heteroxenous group con- 

 sists exclusively of parasites of vertebrates including all mem- 

 bers of the order Spirurida, the suborder Dioctophymatina, and 

 representatives of the Triehuroidea, Ascaridoidea and Meta- 

 strongyloidea. Those monoxenous nematodes in which the adult 

 is wholly or partially free living belong to the Rhabditoidea, 

 Tylenchoidea and Mermithoidea and are all parasites of in- 

 vertebrates. The monoxenous nematodes in which the adult is 

 wholly parasitic include the Strongyloidea, Trichostrongyloidea, 

 Oxyuroidea and representatives of tlie Rhabditoidea, Meta- 

 strongyloidea, Ascaridoidea and Monhysteroidea. One com- 

 monly thinks of the groups with this type of life cycle as ver- 

 tebrate parasites yet NeoapJectana. and Ccphalobiiim viicvo- 

 bivorum are rhabditoid parasites of invertebrates, the Thelasto 

 matidae (Leidiincma, Psciidonymons), Rhigonematidae and 

 Ransomnematiiiae are oxyuroid parasites of invertebrates while 

 Longihncca, Rlmbdias, and Sfrontiyloidcs are rhabditoid para- 

 sites of vertebrates and Oiloiifobiii.i is the lone monhysterid 

 parasite of vertebrates. 



CLASSIFRATIOX OF NEMATODES ACCORDIN'G TO LIFE HISTORY* 



I. Vagantia (Free-living nematodes). 



1. Without persistent stage. 

 Enoplidae 



(1) Ejwplus commnnis (Marine) 



2. With persistent stage. 

 Rhabditidae 



(1) Eliabditis strongyloidcs (Soil, sometimes causing der- 

 matitis in dogs). 



(2) Rhabditis coarctnta (Dung, encysting on dung 

 beetles). 



II. Parasitica (Nematodes deriving nourishment from their 

 host). 

 1. Phytoparasitica (Nematode parasites of plants). 



A. Vagrant parasites. More or less migratory, often feed 

 externally, do not permanently localize in part of plant. 

 Tylenehidae 



(1) Criconemoides mutabile — Tagetes erecta (Exter- 

 nal, roots). 



(2) Pratylenchus praicnsis — Cowpea (Internal, roots). 



(3) Aphelenchoides ritzema-bosi — Chrysanthemums 

 (Leaf and bud). 



(4) Ditylenchus dipsaci — Narcissus, onions, clover 

 (Stem, leaf, and bulb). 



B. Semivagrant parasites. (Localize during definite pe- 

 riod of life history.) 



Tylenehidae 



(1) Angnina (ritici — wheat (Stem and seed). 



*In this outline no attempt is made to supply all hosts or to include 

 all nematode life histories. Only examples are given. 



C. Sedentary parasites. (Female does not migrate after 

 maturity.) 

 Tvlenchidae 



(1) 



-Tomatoes, potatoes, tobacco 

 Sugar beets, potatoes 



(3) 

 (4) 



b. 



Uctcrodcra maiioiii- 

 (Roots and tubers). 

 (2) Heterodera schachtii 

 (Roots and tubers). 



Tylenchulus scmipcnetrans — Citrus plants (Roots). 

 Botylencliulus reniformis — Cowpea (Roots). 

 2. ZooparasUica (Nematode parasites of animals). 

 A. Monoxenous (Only 1 animal host in life cycle). 

 AA. Adult stage wholly or partially free-living. 



a. Only larval stages parasitic or semiparasitic. 



aa. Feed in adult stage usually on carcass of host. 

 Rhabditidae 



(1) Rhabditis pellio — Earthworms (Nephridia). 

 Diplogasteridae 



(2) Piisiionchus aerivora — Termites (Head). 



(3) Alloionema appendicidatum — Limax aler 

 (Foot, alternation of generations reported). 



Steinernematidae 



(4) Keoaplectana bibionis — flies (Intestine), 

 bb. Do not feed in adult stage. 



Mermithidae 



(1) Agamermis dccaudata — Grasshoppers (Body 

 cavity). 



(2) Hermit subnigrescens — Grasshoppers (Body 

 cavity). 



(3) AUomerinis myrmecophila — Lasius spp. 

 (Body cavity). 



AUantonematidae 



(4) Choiidronema passali — Popiliu.s interriipiiis 

 (Body cavity). 



Tetradonematidae 



(.1) Trtradoneiiia plicanx — Sciara coprophila 



(Body cavity). 

 .\dult stage partially parasitic, partially free-living. 

 aa. Monogenetic (Without alternation of genera- 

 tions). 

 AUantonematidae 



AUanlonema mirabilc — Hylobiiis abicliis 



(Body cavity). 



Tylenchinema oscindlae — Frit-iiy (Body 



cavity). 



Howardula bcnigna — Cucumber beetle (Body 



cavity). 

 (4) Scatoncma wiillceri — Scatupsc ftiscipes (Body 



cavity, sometimes reproduces several gen- 

 erations in host). 

 (.5) Aphelciichulus diplogaalcr — Ips typographiis 



(Body cavity). 



PdiaxiU/lrncliii.i ditipar — Ips typographiis 



(Body cavity). 



Sphacriilaria bombi — Bumbiis tcrrestris 



(Body cavity). 



Tripius gibbosus — Cecidomyia pini (Body 



cavity), 

 bb. Heterogenetie (With alternation of genera- 

 tions). 

 AUantonematidae 



(1) Fergusobia curriei — One generation in plant, 

 Eiicah/ptiis macrorrhynchia (Leaf and flow- 

 er) other in fly Feriisonina nicholsonia 

 (Body cavity). 



(2) Heterotylenchus abberaiis — One generation 

 bisexual, other parthenogenetic, both in 

 body cavity Hylcmyia antiqiia. 



BB. Adult stage wholly parasitic. 



a. Heterogenetie (Free-living generation sometimes 

 suppressed). 



Strongyloididae 



(1) Strongyloides stercoralis — Man (Small in- 

 testine). 



Rhabdiasidae 



(2) Rhabdias biifonis — Biifo amrricanus (Luug). 



b. Monogenetic. 

 aa. Reproduce in the host. 



Atraetidae 



(1) Probst mayria vivipara — Efjuines (Intestine). 

 Steinernematidae 



(2) Neoaplectana glaseri — Japanese beetle (Body 

 cavity). 



Cylindrogasteridae 



(3) Longibucca lasiura — Lasiurus borealis 

 (Small intestine). 



Diplogasteridae 



(4) Cephalobium microbivorum — Grylhis assimi- 



(1) 

 (2) 

 (3) 



(7) 

 (8) 



244 



