GLOSSARY 269 



Integument. The outer covering or cuticle of the spider or insect 

 body. 



Instar. The period or stage between molts in the postembryonic de- 

 velopment of arthropods. 



Labium. The lower lip of spiders forming the floor of the mouth 

 cavity. 



Maxillae. In spiders, used as a synonym of the endites or coxae of 

 the pedipalps. 



Metatarsus. A principal segment of the legs, the sixth from the base, 

 with tibia at its base and tarsus at its apex. 



Molting. The periodic process of loosening and discarding the 

 cuticle, accompanied by the formation of a new cuticula. 



Mygalomorph. The members of the suborder Mygalomorphae, the 

 tarantulas, trap-door spiders, and all their kin. 



Nephridia. Tubular structures used as excretory organs in annelids, 

 mollusks, etc. 



Ocelli. The simple eyes of insects. 



Ostia. The slit-like openings into the heart of spiders and insects. 



Palpus. The segmented appendage of the pedipalp, exclusive of 

 coxa and endite; in female spiders, simple; in males, bearing a 

 reproductive organ. 



Patella. A segment of the leg between the femur and tibia in the 

 arachnida. 



Pedicel. The attenuated first abdominal segment, or waist, of 

 spiders, which joins the abdomen to the cephalothorax. 



Pedipalps or Pedipalpi. The second pair of appendages of the head 

 of spiders, consisting of a coxal portion to aid in crushing prey 

 and a distal appendage or palpus. 



Postabdomen. In spiders, the anal tubercle; the fused vestigial seg- 

 ments. 



Receptors. The sense organs; specialized structures of the integument 

 that respond to external stimuli. 



Segment. A ring, somite, or subdivision of the body or of an append- 

 age between areas of flexibility. 



Scales. Flattened, modified setae of spiders. 



Setae. The slender hairlike or spinelike appendages of the body. 



Sclerotized. Hardened by deposition of sclerotin or other sub- 

 stances in the cuticule. 



Scopula. A small, dense tuft or more extensive brush of hairs or 

 setae. 



