Insect Study 



385 



Front view of the same nymph. 



Outdoor Studies, Needham. 



Method The work of observing the habits of adult dragon-flies should 

 be largely done in the field during late summer and early autumn. The 

 points for observation should be given the pupils for summer vacation 

 use, and the results placed in the field note-book. 



The nymphs may be studied in the spring, when getting material for 

 the aquarium. April and May are the best months for securing them. 

 They are collected by using a dip-net, and are found in the bottoms of 

 reedy ponds or along the edges of slow-flowing streams. These nymphs 

 are so voracious that they cannot be trusted in the aquarium with other 

 insects ; each must be kept by itself. They may be fed by placing other 

 water insects in the aquarium with them 

 or by giving them pieces of fresh meat. 

 In the latter case, tie the meat to a 

 thread so that it may be removed after 

 a few hours, if not eaten, since it soon 

 renders the water foul. 



The dragon-fly aquarium should have 

 sand at the bottom and some water 

 weeds planted in it, and there should be 

 some object in it which extends above 

 the surface of the water which the 

 nymphs, when ready to change to adults, 

 can climb upon while they are shedding the 

 last nymphal skin, and spreading their 

 new wings. 



Observations on the young of dragon- 

 flies i. Where did you find these in- 

 sects? Were they at the bottom of the 

 pond or along the edges among the water 

 weeds? 



2 . Are there any plume-like gills at the 

 end of the body? If so, how many? Are 

 these plate-like gills used for swimming? 

 If there are three of these, which is the 

 longer? Do you know whether the 

 nymphs with these long gills develop into 

 dragon or into damsel-flies? 



3. If there are no plume-like gills at 



the end of the body, how do the insects move? Can they swim? What 

 is the general color of the body? Explain how this color protects them 

 from observation? What enemies does it protect them from? 



4. Are the eyes large? Can you see the little wing-pads on the back 

 in which the wings are developing? Are the antennae long? 



5. Observe how the nymphs of both dragon and damsel-flies seize 

 their prey. Describe the great lower lip when extended for prey. How 

 does it look when folded up? 



6. Can you see how a nymph without the plume-like gills breathes? 

 Notice if the water is drawn into the rear end of the body and then 

 expelled. Does this process help the insect in swimming? 



7. When the dragon or damsel-fly nymph has reached its full growth, 

 where does it go to change to the winged form? How does this change 

 take place? Look on the rushes and reeds along the pond margin, and see 



The same nymph seen from, above. 



Outdoor Studies, Needham. 



