. Elementary textbook of economic zoology and entomology. Zoology; Insect pests. TRICHINA, HOOKWORMS, FILARIA, ETC. 87 and do not injure the vegetables. No harm will come from eating vegetables that have been visited by these parasites. The Acanthocephala (Gr. akantha, thorn; kephale, head), or thorn-headed worms, include a number of parasitic forms which show extreme specialization in their mode of life. The anterior end is developed into a conspicuous spiny organ for holding on to the walls of the alimentary canal of the hosts in which they live. There is no mouth or digestive organs but the
. Elementary textbook of economic zoology and entomology. Zoology; Insect pests. TRICHINA, HOOKWORMS, FILARIA, ETC. 87 and do not injure the vegetables. No harm will come from eating vegetables that have been visited by these parasites. The Acanthocephala (Gr. akantha, thorn; kephale, head), or thorn-headed worms, include a number of parasitic forms which show extreme specialization in their mode of life. The anterior end is developed into a conspicuous spiny organ for holding on to the walls of the alimentary canal of the hosts in which they live. There is no mouth or digestive organs but the parasite takes its nourishment through the body-wall from the food surrounding it. Echinorhynchus gigas, infesting hogs, is the best known species of this class. In America the larvae of the June beetle, Lach- nosterna, which is the common white grub found in the sod in pasture lands and else- where, serves as the intermediate host for the parasite. Hogs should not be allowed to pasture on lands where the grubs have be- come infected from previously infested hogs. Once pasture land has become infected it should be left for three years to insure the FIG. 30. A maturing of all the grubs that are infected. wheel animalcule, Several other species belonging to this ^Z^ffij^ class are parasites of fishes. living specimen.) ANIMALS OF UNCERTAIN RELATIONSHIP There are two groups of aquatic animals the exact relation- ships of which are by no means agreed upon by systematic zoologists. They are usually supposed to be more nearly related to the worms than to any other group, and as they are not of enough economic importance to be given a separate chapter they may be mentioned here. The Wheel Animalcules, or Rotifers, branch Trochel- minthes (Gr. trochos, wheel; helmins, worm). These are minute aquatic animals which on account of their size were for a long time classed with the Protozoa. But they are really very complex in structure. The anterior end is provided with. Please note that th
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