NOTES ON PEGOMYIA BICOLOR (Wiedemann), A LEAF-MINING FLY NEW TO CANADA

Extract

Egg laid on the under side of the reaf of the Dock (Rumex obtusifolius). Newly hatched larva bites through to the upper surface of the parenchyma, and works under the epidermis, until the leaf presents a blistered appearance. sometimes three or four larvæ are found in one leaf.

Full-grown larva, four-tenths of an inch long, white, semi-transparent. Segments marked with greenish yellow. Head retractile, furnished with a snout-like process, the apparent use of which is to raise the epidermis as the creature feeds. Mouth set back. Alimentary canal visible under the microscope, also two ducts terminating in spout-like organs protruding from what appears to be the upper edge of the somewhat truncated last segment of the larva. The tuberculose spiracles on the second segment very conspicuous; on the third, less so, and so on diminishing.