Economic entomology for the farmer and fruit-grower [microform] : and for use as a text-book in agricultural schools and colleges economicentomolo00insmit Year: 1896 46 AN ECONOMIC ENTOMOLOGY. Fig are predaceous, and live upon others of their kind ; great num- bers are parasites, their prey being other insects of all orders, and in this way forms that depend upon plant life for their sub- sistence are kept within definite bounds. These bounds, though they may vary from year to year, never change much except where man interferes. This subject will be touched upon in an- other place more fully
Economic entomology for the farmer and fruit-grower [microform] : and for use as a text-book in agricultural schools and colleges economicentomolo00insmit Year: 1896 46 AN ECONOMIC ENTOMOLOGY. Fig are predaceous, and live upon others of their kind ; great num- bers are parasites, their prey being other insects of all orders, and in this way forms that depend upon plant life for their sub- sistence are kept within definite bounds. These bounds, though they may vary from year to year, never change much except where man interferes. This subject will be touched upon in an- other place more fully. Except in rare instances insects are of two sexes, male and female, and we nowhere find among them true hermaphrodites. In the plant-lice and gall-wasps we have apparent exceptions ; but these are only apparent. In the female the most prominent sexual organs are the ovaries. These consist of two sets of tubes, one in each side of the abdo- men, usually below the digestive system, united at their base into one larger tube called the oviduct ; the two oviducts unite, just before opening outwardly, into a single chamber called the vagina. The vagina opens out- wardly at the end of the body, sometimes with- out special modification, sometimes by means of a flexible or extensile tube, sometimes as a long, rigid cylinder, and occasionally in the form of a sting. These structures, be they rigid or otherwise, are always called ovipositors, and their function is to place the ^g^ into the position necessary for its best development. Associated with this system are a number of glands, the use of which is either to give a sticky coating to the &g, enabling it to adhere Ovarian tubes of one to the leaf or Other point at which it is laid, or side, in Pohstes, show- ^q supply a poisonous secrctiou, where such is ing eggs in all stages of development, with ncccssary lor defence or for stupefymg prey, nutritive cells,«;«, be- There is also a little sac, attached bv a slender ceptacie; w, ov
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