Per ^- 164 



Peristomium. — The oral margin or border of the 

 mouth of Diptera. (Loew.) (Gr. feri, and 

 stoma, the mouth.) 



Peritracheal membrane. — The ectotrachea. (Gr. 

 'peri and trachys ; and membrane.) 



Peritreme. — The small plate which is perforated by 

 the external opening of the spiracles directly 

 under the fore-wing. (Audouin.) (Gr. feri, 

 and trema, a hole.) 



Peritrophic membrane. — A funnel-shaped fold 

 of membrane situated on the hinder end of the 

 pro vent riculus and enclosing its outlet, extend- 

 ing back like a tube to the anus. (Gr. peri, and 

 trepo, to turn.) 



Perpendicular.- — At right angles to the horizon. 

 (Gr. perpoidiculum, a plumbline.) 



Perpendiculare.— (Head.) Observing the relations 

 of the head to the thorax ; the term is used when 

 its longitudinal diameter forms a right angle ivith 

 the axis of the body. 



Persistent. — Permanent. (L. persisto, to persist.) 



Petiolar. — Pertaining to a petiole. (L. petiolus, 

 a little stalk.) 



Petiolate. — -(Egg). Stalked ; placed upon a stalk. 

 (L. petiolus.) 



Petiole. — A stalk, (F. petiole, a foot-stalk of a 

 leaf. L. pe'.iolum, ace. of petiolus, little stalk.) 



Petiolule. — A small petiole. 



