Penes: open, slit-like structures of the seminal vesicles to the outer surface in Euplectoptera. Penicillate: with a long, flexible brush or pencil of hair: often at the end of a thin stalk. Penicilli: a pair of small style or cerci-like pieces on the tip of the 8th dorsal segment of abdomen of various male Hymenoptera. Penicilliform: pencil-like or shaped. Penicillum: a pencil or brush of long hair attached at the end of a stalk as long as the brush, and folded in a lateral groove in some male moths. Penis: the flexible, membranous, intromittent organ of the male. Pennaceous: = pennate. Fermate: feathered or bearing feather-like processes. Penniform: feather-like in form. Pentagon -um: a five-sided figure with five equal or unequal angles. Pentamera: Coleoptera with 5-jointed tarsi. Pentamerous: species having five-jointed tarsi. Penultimate: next to the last. Peptone: a soluble proteid compound produced by the digestion of albummenoid food substances. Per-: as a prefix, means very: extremely: through. Percipient: with the power of perceiving. Percurrent: running through the entire length. Pereion: the prothorax. Pereipoda: the second and third pair of thoracic legs of larvae, and the 2d pair in adults. Perfoliate: divided into leaf-like plates: applied to antennae with disc-like expansions connected by a stalk passing nearly through their centres: also to any part possessing a well-developed leaf-like or plate-like expansion. Pergamenous: thin, partly transparent: resembling parchment. Peri-: round about. Periopticon: a complex nerve structure back of the basilar membrane of the eye. Pericardial: around, or belonging to the heart. Pericardial cavity: the space between the diaphragm and dorsal body wall, which contains the heart. Pericardial cells: specialized cells, which lie along both sides of the heart, and whose function it is to purify the blood. Pericardial chamber: is the open space around the heart or dorsal vessel. Pericardial diaphragm: a delicate membranous tissue attached to the ventral surface of the heart and laterally to the body wall := dorsal diaphragm wings of the heart. Peri-intestinal: that part of the body cavity around the alimentary canal. Peri-neural: situated around a nerve: the body cavity immediately surrounding the nervous system. Periodical: recurring at regular intervals. Periopticon: third ganglionic swelling of optic tract: see opticon. Peripheral: referring to the outer margin. Peripheria: the entire outline of the body. Periphery: the circumference or outer margin. Peripneustic: larvae which have the spiracles absent on middle and posterior thoracic rings, and present on all other body segments. Peripodal cavities: pouches in the embryo in which the rudiments of the future legs and wings are developed.