338 THE STUDY OF INSECTS 



I. Tongue short and the basal segments of the labial palpi not 



sheath-like; or the labrum is large and free and uncovered. 



Females without a ventral pollen-collecting brush; often with a 



pygidial area. 



J. Tongue short, its apex bifid; labial palpi normal. Female 



only rarely with a pygidial area. Mesepistcrnal suture 



present. Labrum hidden (Prosopinae) Prosopida 



J J. Tongue long or short, but its apex acute; the labial palpi 

 normal or their basal segments sheath-like. Mesepistcrnal 

 suture wanting. (Many.) p. 375 Andrenid^e 



II. Tongue elongate, the basal segments of the labial palpi sheath- 

 like. Labrum not large and free, usually entirely covered by 

 the clypeus, or if somewhat visible, then strongly inflexed. 

 Females without a pygidial area; those of the non-parasitic 

 species with a ventral pollen-collecting brush, p. 377 

 Megachilid^e 



HH. Wings with three submarginal cells. Females without a ventral 

 pollen-collecting brush; often with a pygidial area. 



I. Tongue short, its apex bifid. Labial palpi normal. Females 



rarely with a pygidial area. Mesepistcrnal furrow present. 

 Prosopidce 



II. Tongue long or short, but its apex acute. The labial palpi 

 normal, or the basal segments sheath-like. Mesepisternal 

 suture rarely present. (Most.) p. 375 Andrenid^e 



GG. Females and workers with corbiculae (except Psithyrus). First 

 submarginal cell divided by a transverse, hair-like chitinized streak 

 (base of R s ), rarely indistinct. Marginal cell (2d Ri + R 2 ) rather 

 long and pointed or appendiculate, usually as long as the three 

 submarginal cells taken together, and extending far beyond the 

 apex of the third (R4). Malar space large and distinct. Hind 

 wings stalked, the anal lobe absent. Tongue very long; the two 

 basal segments of the labial palpi and the laciniae elongate, and 

 forming a sheath. Social insects with normally a worker caste 



(except in Psithyrus). p. 379 Bombid^e 



FF. Hind tibiae without apical spurs. Social insects with a worker caste. 



Workers with corbiculae; females without functionally developed ones. 



Marginal cell (2d Ri + R>) long and slender reaching nearly to the 



wing apex. Anal lobe of the hind wing long and scarcely separated. 



Cell 1st M 2 much larger than cell M 4 . Eyes hairy, p. 381 Apid^e 



AA. Without wings. 



B. A "scale" or "node" between the propodeum and the gaster. p. 357. Formicid/E 

 BB. Without a scale or node between propodeum and gaster. 



C. Females; sting well developed, p. 356 Tiphiid^e and MutilliDjE 



CC. Males, or, if females, the ovipositor does not form a sting. Occasional species 

 or genera of several families of the parasitic Hymenoptera. pp. 345 to 355. 



Suborder CHALASTOGASTRA * 



The Saw flies 



This suborder includes the more generalized members of the Hymen- 

 optera, those in which the form of the body is less modified and the 

 venation of the wings less reduced than is the case with other members of 

 the order. 



The basal segments of the abdomen are similar in form and the ab- 

 domen is broadly joined to the thorax as in the more generalized orders 

 of insects. The first abdominal segment is not closely anchylosed to the 

 thorax, forming a propodeum, as is the case in the Clistogastra, and its 

 tergum is usually longitudinally divided on its middle line. 



* Chalastogastra; chalastos (xaXaoros), loose; gastros (vaorpos), the belly. 



