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. 



IY. OKDER. 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- 



onidse). 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 maxillaa well deve- 



