. Manual of vegetable-garden insects. Fig. 230. A tarnished plant-bug feeding, showing the sucking type ofmouth-parts. The development of insects. ]\Iost insects, with the exception of some scale insects andcertain forms of plant-lice, reproduce by means of eggs. Thenewly hatched insect usuallybears little resemblance to theadult. As it increases in size,its skin becomes too small, anew skin is formed beneath theold one and the latter is dis-carded ; this is known as molt-ing. The period between twosuccessive molts is called aninstar. The number of instarsvaries in different insects from Fig.
. Manual of vegetable-garden insects. Fig. 230. A tarnished plant-bug feeding, showing the sucking type ofmouth-parts. The development of insects. ]\Iost insects, with the exception of some scale insects andcertain forms of plant-lice, reproduce by means of eggs. Thenewly hatched insect usuallybears little resemblance to theadult. As it increases in size,its skin becomes too small, anew skin is formed beneath theold one and the latter is dis-carded ; this is known as molt-ing. The period between twosuccessive molts is called aninstar. The number of instarsvaries in different insects from Fig. 231. —Head of the onion mag-. got fly, showing the lapping typeof mouth-parts. three to six or seven; five is the more common number. In some insects the change from the immature condition to the winged adult takes place without any material change in form; in 366 MANUAL OF VEGETABLE-GARDEN INSECTS others the transformation is abrupt and striking. In theformer case the insect is said to have an incomplete meta-morphosis ; in the latter a complete metamorphosis. Incomplete metamorphosis. In this type of development, the immature stages resemblethe adult in form. The wings develop externally as pad-likeoutgrowths of the thorax but do not become functional tillthe adult stage is reached. The immature forms are knownas nymphs. In this type of development, the life cycle of theinsect consists of three stages, viz., the egg, the nymph (three tofive instars) and the adult. The true bugs and grasshoppershave incomplete metamorphosis. Some authors refer to the early nymphal stages of plant-liceas larvfe and to the last nym
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Keywords: ., bookcentury1900, bookdecade1910, bookpublishernewyo, bookyear1918
