ARTHROPODA. 269 



Not living in communities. 



Fore wings larger than hind wings; adult life short. May-flies. 

 Fore wings not larger than hind wings. 



Wings folded over back when at rest. .Agrion (damsel-fly) 

 Wings extended horizontally, when at rest, . . . Dragon-flies. 



84. Key to some common Hemiptera. 



First pair of wings thickened at base. . .Sub-order Heteroptera 



(true bugs). 

 Land bugs. 



Antennae with four joints; outer half of front wing with 



many veins Squash-bug family. 



Outer half of front wing with few veins Leaf bugs. 



Antennae with 5 joints. 



Brown or green ; on fruits, etc. Bad odor . . . Stink-bugs. 



Black, with red-yellow stripes Calico cabbage bug. 



Water bugs. 

 Short antennae. 



Body broad and flat ; front legs "1 Giant water bugs, 



for grasping, j " Electric-light" bugs. 



Body oval or elongated; front legs not for grasping. 



Back flat ; swim right side up Water boatmen. 



Back like keel of beat; swim upside down, 



Back-swimmers. 

 Long antennae. 



Legs long; suited to walking on water. . . Water- striders. 

 First pair of wings not thickened at base . . Sub-order Homoptera. 

 Do not live in colonies. 



Large ; antennae minute ; 3 ocelli Cicadidae (cicadas) . 



Black and green Cicada tibicen 



(Dog-day harvest-fly). 



Black with bands and spots of red ; \ Cicada septendecim 



appears at long intervals, / (i 7 -year locust) . 



Small ; antennae minute ; not more than two ocelli ; triangular 



and of grotesque form Tree-hoppers (Membracidae). 



In colonies on vegetation. 



Small; antennae long; 4 transparent wings, or none; legs 

 long and slender; on leaves and tender growth. . .Aphides 



(plant-lice) . 



Small ; antennae long ; wings usually wanting ; occur in scaly, 

 cottony, or mealy masses anywhere on plants 



Scale insects (Coccidae). 



