SPONGILLA-FLIES — PARFIN AND GURNEY 449 



larger than segments of flagellum (number variable, from about 40-70 

 segments, terminal segment more ovate with acute apex); vertex 

 arched dorsally, with coronal or midcranial sulcus running from pos- 

 terior margin of head to midvertex more pronounced in certain species 

 , (as Sisyra vicaria, fig. 9,a) ; postgena fused with gena, and postocciput 

 fused with occiput; frons separated from genae laterally by the frontal 

 sutures and anteriorly from the clypeus by the frontoclypeal sulcus 

 or "suture," with frontal pits located at anterior ends of frontal 

 suture; clypeus transverse, almost straight (Sisyi^a) or emarginate 

 anteriorly, bearing setae; labrum (fig. 9,c,d) transverse, usually shorter 

 than clypeus, almost straight, slightly rounded or emarginate ante- 

 riorly, lateral margins reaching posteriorly below anteclypeus, with 

 setae, lower surface with one or two minute sensory groups; mandibles 

 (fig. 9,e-h) asymmetrical, acute apically, outer margin convex, inner 

 margin concave with left mandible usually having a more prominent 

 subapical toothlike projection than the right, above which may be a 

 row of short stout setae or small group of bristles on inner surface of 

 each mandible, each mandible with condyle for articulation with 

 postgena; maxillae (fig. 7,g,i,j) consisting of cardo (flexed mesally, 

 with internal, oblique, strengthening ridge), stipes with 5-segmented 

 maxillary palpus (the terminal segment largest and of distinctive shape 

 in various genera), a heavily setose external galea and mesal lacinia; 

 labium (fig. 7,b-h) consisting of the postmentum (somewhat concave 

 posteriorly, slightly narrowed anteriorly), prementum (large, some- 

 times differentiated into posterior and anterior premental plates) with 

 an anterior broad membranous ligula (notched slightly mesoanteriorly 

 and covered with setae and sensory bristles) and 3-segmented labial 

 palpus (thu'd segment varied in shape in different genera); gular 

 region membranous, transparent; labium and hypopharynx closely 

 associated. 



Thorax (fig. 8,b-e,j,k) : Neck joining prothorax to head con- 

 sisting of three pairs of sclerites — the precervicales (laterodorsal 

 sclerites, small, situated just before anterior margin of pronotum), 

 the laterocervicales (bent, with anterior portion running forward to 

 unite with head) , and the postcervicales (posterior to laterocervicales) ; 



' prothorax with pronotum usually broader than long, sometimes with 

 depressions, elevations, or grooves dorsally, sometimes overlapping 

 the cervicales and dorsal portions of pleural sclerites (the epimeron 

 and episternum, which are reduced and united to almost form a 

 single plate, epimeron ventrally produced into a rounded process 

 articulating with coxa), sternum mostly membranous except for a 



' 'transverse basisternum between coxae, small trochantin just below 

 ventral margin of episternum; meso thorax largest, mesonotum large, 

 with scutum divided into two convex lobes by deep median sulcus 



