. Manuale di natura-studio per insegnanti e genitori, basato sulla natura di Cornell-studio di volantini. Lo studio della natura. la loro dimensione. Il Dragon Fly di uova sono poste in acqua; in alcuni casi essi sono semplicemente lasciato cadere e affondano sul fondo; ma nel caso della fanciulla-vola, la madre perfora i gambi delle piante acquatiche e luoghi le uova al loro interno. La ninfa in nessun saggio assomiglia al genitore dragon-fly. Si tratta di uno squallido piccola creatura, con sei queer, ragno-come gambe e nessun ali; anche se ci sono quattro little wing-pad che si estende verso il basso la sua schiena che inglobano il crescente ali. Esso può rimanere nascosta

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. Handbook of nature-study for teachers and parents, based on the Cornell nature-study leaflets. Nature study. their size. The dragon-fly's eggs are laid in the water; in some instances they are simply dropped and sink to the bottom; but in the case of damsel-flies, the mother punctures the stems of aquatic plants and places the eggs within them. The nymph in no wise resembles the parent dragon-fly. It is a dingy little creature, with six queer, spider-like legs and no wings; although there are four little wing-pads extending down its back, which encase the growing wings. It may remain hidden in the rubbish at the bottom of the pond or may cling to water weeds at the sides, for different species have difi^erent habits. But in them all we find a most amazing lower lip. This is so large that it covers the lower part of the face like a mask, and when folded back reaches down between the front legs. It is in reality a grappling organ with hooks and spines for holding prey; it is hinged in such a manner that it can be thrust out far beyond the head to seize some insect, unsuspecting of danger. These nymphs move so slowly and look so much like their background, that they are always practically in ambush awaiting their victims. The breathing of the dragon-fly nymphs is peculiar; there is an enlargement of the rear end of the alimentary canal, in the walls of which tracheae or breathing tubes extend in all directions. The nymph draws water into this cavity and then expels it, thus bathing the tracheae with the air mixed with water and purifying the air within them. Expelling the water so forcibly, propels the nymph ahead, so this act serves as a method of swimming as well as of breath- ing. Damsel-fly nymphs, on the other hand, have at the rear end of the body, three long, plate-like gills, each ramified with tracheae. Nymphs grow by shedding the skin as fast as it becomes too small; and when finally ready to emerge, they crawl up on some object out of the water, and molt f

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• bookcentury1900
• bookdecade1910