. The animans and man; an elementary textbook of zoology and human physiology. several yards long. (After Lenckart.) other organs and tissue of animals. Over seven hundredand fifty kinds of these Sporozoan parasites have been de-scribed. Some of them, as has already been told in Chap-ter XII are parasites of the human body causing terribleinfectious diseases among us. Parasitic insects.—Among the insects many live as para-sites during their immature or larval life, but as adults 416 THK ANIMALS AND MAN are free and independent creatures. From the chrysalidof a butterfly or moth there will ofte
. The animans and man; an elementary textbook of zoology and human physiology. several yards long. (After Lenckart.) other organs and tissue of animals. Over seven hundredand fifty kinds of these Sporozoan parasites have been de-scribed. Some of them, as has already been told in Chap-ter XII are parasites of the human body causing terribleinfectious diseases among us. Parasitic insects.—Among the insects many live as para-sites during their immature or larval life, but as adults 416 THK ANIMALS AND MAN are free and independent creatures. From the chrysalidof a butterfly or moth there will often come not a butterflybut numerous tiny four-winged gnats, called ichneumonflies. This is what happened. When the butterfly cater-pillar was crawling about a female ichneumon darted downon it, and with her sharp ovipositor either laid several eggsbeneath its skin or glued them to its outer surface. Theseeggs hatched in two or three days as tiny white ichneumongrubs, which immediately burrowed deep into the cater-pillar and lay there feeding on the blood and tissues of its. FIG. 208. Larva of a sphinx moth, with cocoons of a parasitic ichneumonflv. (Natural size.) j fly. (Natural size.) body. But the caterpillar went on eating and finally changedinto a chrysalid, with the ichneumon grubs still inside. Soonthe grubs, having eaten up most of the body of the developingbutterfly and thus killed it, changed into tiny pupae, andlater into fully developed ichneumon flies which gnawedtheir way out through the horny case of the dead of the most interesting ichneumon flies is Thalessa,which has a remarkably long, slender, flexible insect, known as the pigeon horn-tail (fig. 209),upon which Thalessa preys, deposits its eggs by means ofa strong, piercing ovipositor, half an inch deep, in the trunksof growing trees. The young or larval horn-tail hatches
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