Sub-family. Metastrongylinæ, Leiper, 1908.
Buccal capsule absent or slightly developed, vagina elongate, uteri convergent[307] and have a simple musculature. Parasitic in the respiratory or circulatory system. Genera: Metastrongylus, Synthetocaulus.
Genus. Metastrongylus, Molin, 1861.
Mouth with six lips, of which the two lateral are the largest. Postero- and postero-external rays[308] of bursa thin, the rest thick. Only the median ray double. Spicules very long and slender, striated. Vulva immediately in front of anus. Eggs contain an embryo when laid.
Metastrongylus apri, Gmelin, 1789.
Syn.: Gordius pulmonalis apri, Ebel, 1777; Ascaris apri, Gmelin, 1789; Strongylus suis, Rud., 1809; Strongylus paradoxus, Mehlis, 1831; Strongylus elongatus, Duj., 1845; Strongylus longevaginatus, Dies., 1851.
The male measures 12 to 25 mm. in length; the bursa is bilobed; there are five rays in each lobe; the spicules are thin and up to 4 mm. in length. The females measure 20 to 50 mm. in length, the anus is close in front of the posterior extremity, which has a recurved, hook-like process; the vulva is close in front of the anus. The eggs are elliptical, 57 µ to 100 µ in length, 39 µ to 72 µ in breadth; when the eggs are deposited the embryo is already formed, 220 µ to 350 µ by 10 µ to 12 µ.
Fig. 308.—Metastrongylus apri: one side of bursa. a., anterior; a.e., antero-external; a.m., antero-median; p.m., postero-median; p.e., postero-external; p., one division of posterior ray. (Stephens.)