34 



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



CLASSIFICATION OF INSECTS. 



The following analytical key has been adapted from the 

 key arranged by Prof. H. E. Summers and given in Kellogg's 

 American Insects. It applies only to adult insects. 



Key to Orders. 



1. Mouth-parts projecting, or not withdrawn into a cavity 



in the head. Normally with wings, which are some- 

 times rudimentary or wanting 2 



Mouth-parts withdrawn into a cavity in the head. 

 Wingless insects, sometimes having abdominal legs, 

 and feet having one or two claws THYSANURA 



2. Mouth-parts fitted for biting; abdomen broadly joined 



to thorax ; feet never bladder-shaped 3 



Mouth-parts fitted for sucking, sometimes in part for 

 biting. In latter case, either the base of abdomen is 

 usually strongly constricted and joined to thorax by 

 a narrow peduncle, or the tarsi are bladder-shaped 

 without claws I 4 



3. Rear end of abdomen without prominent un jointed ap- 



pendages resembling forceps 4 



Rear end of abdomen with prominent appendages re- 

 sembling forceps ; fore wings, when present, short, 

 veinless, horny or leathery EUPLEXOPTERA 



4. Fore wings not membranous 5 



Fore wings, if present, membranous like rear wings ; 



latter occasionally, but not usually, folded like a fan 6 



5. Fore wings, if present, leathery, usually with many 



veins, and thicker than the rear wings, which are 

 folded lengthwise like a fan. If wings are absent, 

 labium is cleft in middle and prothorax is large 



ORTHOPTERA 

 Fore wings, if present, veinless, horny or leathery; if 

 absent, labium is entire COLEOPTERA 



6. Antennae inconspicuous 7 



Antennae conspicuous 8 



7. Rear wings smaller than fore wings; posterior end of 



abdomen with two or three many- jointed filaments 



EPHEMERIDA 



