V-^^r^: :■" 





Dermtttoxys veliffern, Phofnmicrograph of fourth stage larva pene- 

 trating mucous membrane. After Wetzel. li>31. J. Para.sit. v. 18. 



Asrnriilia finjli. 

 erts. 1H:i7. Bull. 



Fig. 188. 



Section nf small intestine showing larva. After Rob- 

 .\'fi. 2. Animal Health Sta. Yeerongpilly. Queensland. 



The life cycle of Ascaridia galli ma.v well be a second step 

 towards that of Ascaris. As elucidated bj- Ackert (1931), 

 Alieata (1934) and Roberts (1937) this worm undergoes one 

 molt in the egg and then normally remains enclosed in the egg 

 until infection. There are three molts in the host, the tirst of 

 these (second molt) occurring about (3 days after infection and 

 the others at about 6-day intervals thereafter. After reaching 

 the third stage, on about the ninth or tenth days, the larvae 

 Inirrow down between the villi and penetrate into the glands of 

 Lieberkuhn, the posterior ends of the bodies remaining free in 

 the lumen. Itagaki (1927) observed that at certain seasons in 

 Japan (midsummer and midwinter) the larvae habitually pene- 

 trated into the mucosa, about as described by Ackert and by 

 Roberts, causing fibrous nodules, but that in spring and autumn 

 they remain in the lumen. Roberts reported less tendency for 

 the larvae to burrow into the mucosa in April and May than 

 in November. Although on rare occasions the larvae penetrate 

 too deeply and enter the peritoneal cavity, mesenteries, liver. 

 or even the lungs (Ackert, 1923; Guberlet, 1924), it is clear 

 that this is purely accidental. 



Svbuhira iriimpti. according to Alieata (1939), has depart- 

 ed from the usual heterakid life cycle pattern in requiring an 

 intermediate host. This is the only member of the subfamily 

 Subulurinae in which the life cycle has been investigated, and 

 it is possible that the use of an intermediate host has become 

 general in this group as it has in the Anisakinac. 



Alieata was unable to infect chickens by feeding embryonated 

 eggs, either just recovered from the uteri of gravid females, or 

 incubated in \vater at about 24° C. for 1 week, but succeeded 

 in producing infection by feeding naturally infected arthro- 

 pods harboring the cysts in the body cavity. The cysts contain 

 coiled nematodes having bulbed esophagi and conspicuous 

 esophageal valves as in the adults (Fig. 1S6, JJ). High inci- 

 dences of natural infection were found in the following arthro- 

 pods collected on poultry farms in Hawaii: (Coleoptera) Der- 

 mestes vulpinus, Gojioccphalus scriatum, Ammoplwnis insiilaris, 

 Alphit oh hits diapcriniis ; and (.Dermaptera) EiibonlJia ainin- 



lipes. Encysted larvae were also found in grasshoppers (Con- 

 ocephalns aallalor) l.'i days after experimental infection. 



CoSJIOt'ERCIDAE 



At least some of the members of this family resemble the 

 typical Ascarididae in that the larvae, burrowing into the 

 mucosa, enter the circulatory system and reach the lungs, where 

 they escape into the air spaces and eventually make their way 

 back to the intestine via trachea and esophagus. They differ, 

 however, in having a free living phase outside the body. Cos- 

 mocerca trispinosa (= Nematoxys longicaiida) has long been 

 known to occur in the lungs of salamanders in an immature 

 form, and in the intestine as an adult. Von Linstow considers 

 its growth in the lungs as analogous to the growth of Ani- 

 sakinae in an intermediate host. Harwood (1930) found that 

 Cosmocercoides dukac (his Oxi/somatium variabilis) undergoes 

 a molt after 5 days of free life outside the bod.v and, although 

 his observations on development after infection are inconclu- 

 sive, that the larvae are found in the lungs not only after sub- 

 cutaneous inoculation, but also after infection by mouth. They 

 do not, however, penetrate the skin. 



Ascarididae 



The ma.)ority of the Ascarididae have a migratory phase lie- 

 fore becoming adult in the intestine. The larvae, burrowing 

 into the mucosa, enter the circulatory system and are cariiod 

 via liver or lymphatic system to the heart, thence to the lungs 

 where they become free in the air spaces, and thence via trachea 

 and throat back to the alimentary canal. Toxascaris leonina, 

 according to Wright (1935), does not perform this migration; 

 the life cycle is similar to that of Ascaridia except that the sec- 

 ond-stage larvae burrow into the mucous membranes almost 

 immediately after hatching, and return to the lumen of tlie 

 intestine after the third molt, on the 9th or 10th day. As 

 shown by Fiilleborn (1922) and others, some larvae penetrate 

 all the way through into the liody cavity and enter viscera by 



280 



