30 Key to Families of North American Insects. 



99. Fore wings with two cubital cells; labial palpi with the basal joints much elon- 

 gated, the apical minute; underside of abdomen of female with a pollen- 

 collecting scopa, except in the parasitic genera. (Coelioxys, Megachile, 



Heriades, Osmia, Stelis, Anthidium.) MEGACHiLID.E 



Fore wings always (in our species) with three cubital cells, the marginal cell 



narrow and as long as the cubitals united 100 



100. Hind tibia and tarsus of female with a dense pollen-collecting scopa; stigma 



obsolete; large robust bees, mainly tropical. (Xylocopa) . . XYLOCOPID.^ 



Hind tibia and tarsus of female without distinct scopa; stigma large; small 



bees. (Ceratina) CERATINID^ 



ORDER COLEOPTERA. 



{ELFMTERA TA; ELY THRO PTERA.) 



Moderate-sized, small or minute, more rarely very large, hard- 

 bodied insects; head free, usually prominent; mandibles well 

 developed; antennae ten- or eleven-jointed, sometimes less, very 

 rarely more; ocelli nearly always absent; pro thorax free; two pairs 

 of wings, the front pair (elytra) thickly chitinized, sheathing the 

 meso- and metathorax and also nearly always the abdomen, 

 almost always meeting in a straight line down the middle of the 

 back; hind wings occasionally absent; legs homonomous, the tarsi 

 usually with five or four joints; no cerci. Metamorphosis com- 

 plete, the larvae mandibulate. A very large and widely distributed 

 group, including beetles and weevils. 



1. First ventral segment di\'ided by the hind coxal cavities (except the rare Cupe- 



didse) so that the sides are separated from the very small median part, the 

 first three ventral segments immovably united; antennae thread-like or 

 nearly so; hind wings with one or two crossveins near the middle, connecting 

 the first and second branches of the media (PI. 7, figs. 158, 159); almost 



always carnivorous and predatory. Suborder ADEPHAGA 2 



First ventral segment visible for its entire breadth; wing without such cross- 

 veins (PI. 7, figs. 160, 161). Suborder POL^PHAGA 8 



2. First three ventral segments immovably united 3 



Abdomen with five free ventral segments; metasternum with a piece in front 



of the hind coxae marked off by a distinct suture; rare bark beetles. (Cupes.) 



CUPEDID^ 



3. Metasternum with a transverse triangular antecoxal sclerite separated by a well 



marked suture, reaching from one side to the other and extending between 



the hind coxae (PI. 6, fig. 108) 4 



Metasternum with a short antecoxal sclerite, not prolonged posteriorly between 

 the coxae, the suture indistinct; rare semiaquatic beetles. (Amphizoa.) 



AMPHIZOIDiE 



