214 MANUAL OF NATURAL HISTORY. 



objects passed without a thought by thousands, are 

 often those which produce imperceptibly, yet not 

 less certainly, most important, changes around us. 



IV. ORDER. — Net-winged Insects (Neuroptera). 



Wings four, long, membranous, transparent, tra- 

 versed by a net-work of nervures, lie flat on the back, 

 carried erect or horizontally when at rest, ante- 

 rior and posterior pairs often of equal size, posterior 

 pair sometimes very small ; antennae variable, mi- 

 nute, and setiform, or long, filiform or setaceous ; 

 legs moderate ; abdomen more or less lengthened, 

 cylindrical or depressed, sometimes terminated by 

 filaments. 



1. Family — Day-Flies (Ephemeridae). Head small; 



eyes large and oval ; antennae very short ; 

 body long, slender, soft, terminated by long 

 filaments ; wings carried erect when at rest, 

 posterior pair small or wanting; tarsi 5-jointed. 



2. Family. — Hammer-headed Dragon-Flies (Agri- 



onidae). Head hammer-shaped ; eyes round, 

 lateral, widely separated ; mandibles and 

 maxillae well developed ; antennae very short ; 

 abdomen long, slender, cylindrical ; wings of 

 equal size, gradually increasing in breadth 

 from the base to near the apex, meeting each 

 other, and carried erect when at rest. Flight 

 feeble and heavy. 

 3. Family. — Dragon- Flies (Libellulidae). Head 

 large ; eyes very large, approximate on top 

 of head ; mandibles and maxillae well deve- 



