REPRODUCTION. The flies forum a very large group, eomprising more than .I0,000 described species, and in 11111111)Cr of individuals it is un excelled by any other group of insects front the prolificacy and rapid breeding of the many forms. Some curious biological phenomena occur in this group. In a great many flies, b»r example, the eggs hatch \tit hill the body of the insect, and the living larva. are deposited. With the group known is the Pupifera, even the larval development is undergone in the body of the and the insect is deposited in the pupal condition. The phenomenon known as medogenesis also occurs, and the hirv:e of a certain midge are known to give birth to young while yet in the larval condition. The metamorphoses of dip terous insects are more complete than those of any other order of insects. The larva is com monly termed a grub, or maggot, and is foot less and frequently almost structureless. In
many species the dura tion of the larval stage is very short. The maggot feeds voraciously, grows with extraordinary raphl ity, and transforms to pupa either within the last larval skin or into an appendage - bearing pupa similar to that of pertain I fymenop tern or Lepidopt era . The ent forms vary greatly in habits. Very many are feeders on decaying animal and vegetable mat ter. Others a re ON warm-blooded animals.
Many forms all' aquatic.
Others feed upon living vegetation, while others form galls upon different plants. Among the plant-feeding flies, some species have high rank as injurious insects. as the lfessian fly and the onion-maggot, the apple-maggot, and others, while whole regions are rendered almost uninhabitable by the presence of forms which annoy men and an imals.