186 Illinois State Laboratoi'y of Natural History. 



tact, or one or both of these separated by the hind 

 tarsi, making a group of four to six tarsi in contact 

 side by side. 



Head chitinous, either imperfectly or fully developed. 

 Pupa exposed, or concealed in the last larval skin. 

 The latter opens for the emergence of the pupa or 

 imago by a longitudinal dorsal split, enlarged by 

 transverse splitting so as to form a T or I-shaped 

 opening OrthorhapJia. 



Head feebly differentiated, membranous above; body 

 generally twelve-jointed, with only posterior or with 

 anterior and posterior stigmata. Pupa concealed in 

 the indurated subcylindrical last larval skin, which 

 opens for the escape of the imago at the anterior end, 

 either by a horizontal split over the mouth extending 

 back to the fifth segment, or by a vertical entire or par 

 tial encircling split also, so that the anterior end, or 

 only its upper half, comes off like a coh^.. Cycler kapha. 



Orthorhapha — La^voB. 



Mandibles opposed, with biting horizontal movement. 

 [Fig. 16.] {Nematocera.) 

 Body ending in a chitinous respiratory tube; no false 



feet on prothorax. (Moth Flies.) Psychodidoe. 



Posterior respiratory tube, when present, not chi- 

 tinous. 

 Head incomplete, small, retractile, not containing 

 nerve ganglia; body segments twelve, abdom- 

 inals in part often divided by a pseudo-suture 

 into two divisions; posterior stigmata usually 

 protected by fleshy teeth. [Fig. 24.] (Crane- 

 flies.) TipulidcB. 



Head fully developed, not retractile, containing th^ 

 flrst ganglia. [Fig. 16.] 

 Last segments drawn out into a very long mem- 

 branous respiratory tube; false feet on some of 

 the anterior abdominals Ptychopteridce. 



