56 ELEMENTARY LESSONS ON INSECTS 



without food. While it is resting quietly, liberate & 

 mosquito "wriggler" (or any other suitably small 

 living and active aquatic animal) close in front of it, 

 and see what happens. The stroke of the labium is 

 so swift the eye cannot follow it; but a flashlike move- 

 ment is seen, and then there is a struggling captive 

 held close to the terrible jaws.* 



B. Study Preserved Material. 



a. The Adult 



A few of the more striking characters of a dragonfly were 

 noted in the first lesson (see p. 15). With one of the larger 

 dragonflies in hand, note further: 



I. In the head. 



1. The typically carnivorous mouth parts: everything 

 fitted for capturing prey: mandibles, maxillae, and 

 even the lobes of the labium sharply toothed. 



2. The shelf -like prominence above the mouth — a sort of 

 "cubist" nose, with three shining beadlike ocelli above 

 it and the bristle-like antennae arising farther out at 

 the sides. 



3. The very great number of facets (try counting them) 

 making up the compound eye, and the difference in size 

 between those of the upper surface and those below. 



4. The concavity of the rear of the head. 



* Dragonfly nymphs will take only living and actively moving prey; 

 but in absence of suitable food, they may be induced to grab a bit of 

 earthworm or even of beefsteak, if the bit is held with a forceps or on a 

 needle point and wriggled in front of the nymph within reach of its labium. 



