28 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [Bull. 



is known as the ocellar basin. The ocellar basin varies greatly in 

 form and extent in the different families and subfamilies. 



Frontal Furrow. — The frontal furrow is a well marked de- 

 pression occurring on the meson of the ocellar basin of many 

 species. It may be limited to a pit or fovea, or it may extend 

 from the median ocellus to the frontal crest. It may not only 

 vary in length, but may vary in position and be located anywhere 

 in the space between the median ocellus and the frontal crest. 

 There is also considerable variation in the width of the furrow. 



Malar Space. — The malar space is the area on each side of 

 the head included between the proximal end of the mandible and 

 the ventral end of the compound eye. 



Key to Families. 



1. Front wings with free part of Rj present; antennae always 



with more than three segments, third segment of antennae 

 usually longer than all the following segments together 



XYELID^ p. 29 

 Front wings with free part of Rs always wanting; antennae 

 with three or more segments, third segment never as long 

 as all the following segments together; if third segment 

 be long, antennae consisting of only three segments 2 



2. Front wings with base of subcosta always present; pronotum 



transverse and scarcely emarginate behind 



PAMPHILIID^ p. 32 

 Front wings with base of subcosta wanting, at most repre-r 

 sented only by a pale indistinct line; subcosta usually 

 represented by the free part of Sci, which appears like a 

 cross-vein in cell between costa and R+M; pronotum 

 transverse but frequently so deeply emarginate behind 

 that the mesal portion is concealed by the head 3 



3. Front wings with radial cross-vein received in cell R4, very 



rarely in cell Ro; medio-cubital cross-vein joined to 

 R + M or to M; if joined to M, first abscissa of M not 

 more than one-sixth the length of the cross-vein; oviposi- 

 tor in form of a saw, exserted or retracted; anterior tibiae 



with two apical spurs TENTHREDINID^ p. 41 



Front wings with radial cross-vein received in cell Rs, 

 rarely in cell R4; if in cell R*, medio-cubital cross-vein 

 joining media distinctly distad of radius and subequal in 

 length to first abscissa of media; ovipositor in form of a 

 saw or borer and usually exserted; anterior tibiae with one 

 apical spur 4 



