The eggs of Rhabdophaga strobiloides are laid in the spring in the buds of willow trees. The presence of the larva causes the development of a gall resembling a pine cone. The larva feeds on the interior of the gall during the summer and winter, becoming an adult the following spring. The female of another member of the family, Cecidomyia albovittata, lays its eggs between the leaves of the pine cone gall, doing no harm to the gall-former. Two pests of clover are the clover-leaf midge, Dasyneura trifolii, which ruins the leaves of the plant, and the clover flower midge, D. legumnicola, whose larva destroys the seed. The hessian fly, Phytophaga destructor, brought to the United States from Europe during the 18th century, causes wheat, rye, and barley plants to break and bear few seeds. The wheat midge, Thecodiplosis mosellana, also ruins wheat crops. The eggs are laid in the flower and the larvae eat the pollen and seed contents.
The eggs of the pear midge, Cantarina pyrivora, are laid in the unopened flower buds of the pear tree and the fruit is ruined by the larvae. The eggs of certain species belonging to the genus Miastor develop by means of parthenogenesis (from unfertilized eggs), the young frequently eating their mothers.
