that I'KK" iMiiitsiiiiinp motile laivm- :iro not infective. Alieala 

 (1!<34) found tliat tlio larva of IlUillirola bhiltar, a closely 

 rolatod llielastoniatid, molts in the okr before reaeliins the in 

 feetive since and while Dotirovolny and Aekort do not men- 

 tion the matter their liRnres indieate that L. (ipixniliciilalum 

 undergoes a similar molt. If kept moist at room temperatnre 

 and in sniidned lifrht infeetive vjxiix remain viable for a eonsid 

 erable time bnt are killed by jiroloiiK'ed exposnre to direct snn 

 light. Infective egRs are inRcsted by the insects and li.itih in 

 the posterior part of the midgnt. 



Dobrovolny and .\ckert kept heavily infected cockroaches in 

 enptivity for more than a year and -saw no evidence that tlu' 

 insects were markedly affected by the parasites. 



Body Cavity and Tissue Parasites 



This (jroup imindes wh.it are, i)erluiiis, our oldest jiarasitic 

 nematodes in the sense that their ])riiKenitors w<'i'e t\w first to 

 assume a parasitic mode of life and throuKli the aRcs they have 

 become very highly adapted to this way of living. Some of the 

 allantonematids have become almost incrednlously si)eciali/.ed in 

 morplK)logy, liehavior and host parasite relationships and among 

 them are to be found some of the most unusual nematodes 

 known. 



MVEXCIlin.VE 



This is a small and comparatively little known group of nema- 

 todes that are parasites of amphibians and leeches. The sys- 

 tematic position of the family is somewhat questionable but 

 investigators who have studied the group regard it as probably 

 related to the Tylenchidae. Both se.xes arc characterized by a 

 medium sized stylet without basal swellings and by a peculiar, 

 sucker-like organ situated on the mid ventral surface about one- 

 fifth of the distance from head to tail, this latter presumably 

 marking the position of the excretory pore. Two species have 

 been reported from leeches. 



MvENClirs BOTHRVOPHORUS Schuberg, 1004, was found in 

 iTcrnuiny ]>arasitizing the leech, KnipobthUit ortocuIaUt (L.) 

 (Syn. S'cpliclix viilgari.s (Miiller) iloi). Tand.). Different stages 

 of the nematode, including sexually mature individuals (Fig. 

 107 .-V & B), occurred in the connective tissues and larvae were 

 found within the muscle cells (Fig. 167 C). Adults were also 

 found in the cocoons of the leech. All the details of the life 

 cycle are not known with certainty but Schuberg and Schroder 

 (1904) concluded that larvae undergo the first part of their 

 development within the muscle cells, then leave this location 

 and enter the connective tissues where they continue develop- 

 ment to sexual maturity. From this point on the life cycle 

 is apparently continued outside the Iiost, presumably in the 

 cocoons. Schuberg and Schroder suggest that the nematodes 

 reach the cocoons either by penetrating into the gonads and 

 passing out with the reproduction products or b3' penetrating 

 directly through the body wall and entering the cocoon while 

 this structure still encompasses the body of the leech. The fact 

 that the i>arasites are frequently found in the connective tissues 

 immediately underlying the epidermis of the leech seems 

 to make the latter alternative all the more probable. Schuberg 

 and .Schriider concluded that the females lay their eggs within 

 the cocoons and that the resulting larvae infect the young 

 leeches. How the parasite enters the host has not been deter- 

 mined. 



Myen-cius botelhoi Pereira, 1931, is a parasite of the leech, 

 Limnobdella bra.'iiUensi.s Pinto, and was found and studied in 

 Brasil. According to Pereira (1931), infected leeches harbored 

 the nematode in all stages of development. The epididymus was 

 a favored location but the parasite was found in other connec- 

 tive tissues tliimgh rarely in the muscles and never in the ali- 

 mentary tract. Apparently the worms occurred between but 

 not within the cells. The outstanding point of interest regard- 

 ing this nematode is the fact that Pereira found it regularly 

 within the sjiermatophores of the leech. It would appear, there- 

 fore, that the parasite enters the spermatophores at some time 

 during their formation or passage out of the leech and uses 

 them as a vehicle for transmission from host to host. 



DRlLONEMATrD-IE 



This is a small family of about a dozen genera that arc cither 

 monotypic or contain only a few species each. These nema- 

 todes are parasites of earthworms and occur in the coelomic 

 cavities, in or associated with the reproductive organs or em- 

 bedded in the muscles. Many of the species are characterized 

 by large, sometimes almost sucker-like, phasmids and some of 

 the species by large cephalic hooks. Very little is known about 

 life cycles. 



DiCELis FiLARi.\ Dujardin, 184.i. — Of the specimens of Liim- 

 bricus rubelluit Hoff., collected by Wiilker (1926) in Germany 

 near Frankfort a. M., about 2.^ percent harbored this parasite 



(Fig. 1(17 10 \- F) but other species of earthworms collected in 

 the .s.ime region were not infected. The usual number of nema- 

 todes per host was 6 to H with a maximum of 22, females gen 

 erally outnumbering nmles. The parasites occurred in the body 

 cavity of the host in the region of the reproductive organs but 

 not in the nephridi.-i. 



The covering of the egg (Pig. ]()7 D) is thick with a rough 

 outer surface indicating that the shell proper is probably cov- 

 ered by an external coat and suggesting that the egg is 

 e(iuipped to resist adverse conditions and jiersist in the soil for 

 .1 considerable period. lOggs are laid in the body cavity of the 

 host but do not continue development in this location. Wiilker 

 did nut (iinl larv;il stages either in earthworms or in surround 

 ing soil and was unable to follow the life cycle. It is not 

 known how eggs are expelled from the host, or in what stage, 

 the p;irasites enter. Wiilker demonstrated that if the earth 

 worm dies these nematodes are unalile to reproduce in the car- 

 cass but perish with the host. 



■1 l-:TKM)ONKM.\Tin.\E .\XD MKR.MITHIDAE 



To the family Tetradonematidae there have, as yet, been as- 

 signed only two sjiecies, Tetradoncma pUcan.i and Aproctonema 

 rntomophaiinm. These, essentially, are primitive mermithids 

 and must be included in any general consideration of life 

 cycles in this group. 



Fig. 107. .MYENCHIDAE AND DRILOXEMATIDAE 



A-C — Miienchuit bothryophorus (A — Adult female; B — Adult male; 

 C — Larva in muscle cell). D-F — Dicelis filaria (D — Eggs; E — Adult 

 male; F — Adult female). A-C, after Schuberg and Schroder, 1904: 

 D-F, after Wiilker, 1926. 



251 



