38 EXPLANATION OF TERMS 



Dimerous: having only two tarsal joints. 



Dimidiate -us: halved; extending half way around; applied to elytra when 



they cover only half the abdomen. 

 Dimidius: of half length. 



Dimorphic: occurring in two well-marked forms. 

 Dimorphism: a difference in form, color, etc., between individuals of the 



same species, characterizing two distinct types : may be seasonal, sexual or 



geographic. 



Dioecious: with distinct sexes. 



Dioptrate: an ocellate spot with the pupil divided by a transverse line. 

 Dioptric: with a transversely divided ocellus. 

 Diploglossata: an ordinal term proposed for Hemimerida, because of the 



supposed presence of a second labial segment. 

 Diplogangliata: applied to the Arthropods. 

 Diploptera: = diplopteryga ; q. v. 

 Diplopteryga: Hymenoptera; wasps in which the wings are longitudinally 



folded when at rest. 



Dipneumones: having two lungs (certain spiders). 

 Diptera: an ordinal term applied to insects having only one pair of wings 



(anterior); thorax agglutinate; mouth haustellate; transformations com- 

 plete. 



Dipterocecidium: a gall formed by a dipterous insect. 

 Dipterous: belonging to or having the characters of Diptera. 

 Direct: applied to metamorphosis = incomplete. 

 Directive coloration: directive marks or colors which tend to divert the 



attention of an enemy from more vital parts. 

 Disc: see disk. 



Discal: on or relating to the disc of any surface or structure. 

 Discal area: of a wing applies especially to the more central portion, or that 



area covered by the discal cell. 



Discal bristles: Diptera; are inserted on the middle of the abdominal seg- 

 ments before the hind margin. 

 Discal cell: Lepidoptera; the large or median cell extending from the base 



of the wing toward the center: = radial cell (Comst.) : in Diptera (Will.) 



= 1st medial 2 (Comst.) : Odonata; = discoidal areolets, q. v. : Triclwp- 



tera, the cell between the forks of the radial sector, and separated from 



the 2d apical cell by a cross-vein. 

 Discal patch: in some male Hes per idee the oblique streak of specialized black 



scales on the disc of the primaries. 

 Discal vein: Lepidoptera; the cross-vein closing the discal or median cell; 



extends from radius 5 to media 1. 

 Disciform: formed or shaped like a disc. 



Discocellular nervure or vein: Lepidoptera; = discal vein, q. v. 

 Discoidal: relating to the disc, or middle = discal. 

 Discoidal area: the middle area or field: Orthoptera; that area of the teg- 



mina between the posterior or anal and the anterior or costal areas : = d. 



field. 

 Discoidal areolets: Odonata; a varying number of rows of cells on the outer 



side of the triangle between the short sector (M 4 of Comst.) and the 



