44 



INSECTS. 



soon as it is thoroughly stupefied by the poison, but not 

 killed, turn it out again upon a paper, and study its re- 

 spiratory movements. Note the regular expansion and 

 contraction of its abdomen, and search with a lens for 



the minute openings 

 of spiracles on each 

 abdominal segment. 

 Two larger spiracle 

 orifices may be found 

 on each side of the 

 thorax. 



Observe the spin- 

 dle-shaped body; the 



DRAGON FLY (natural size). 



rounded head, con- 

 . cave behind; the wide 

 thorax; the angled and tapering abdomen. 



I. The Head. Note the enormous development of the 

 eyes. 



Find a minute single eye (ocellus) above the base of each 

 antenna, arid another on the median line slightly farther 

 forward. 



Remove an antenna entire, and examine with a micro- 

 scope. Compare with the antenna of a butterfly. Draw. 



Turn to the mouth. Find an upper, movable lip (the 

 labrum) and a larger, two-cleft, lower lip (the labiurn). 

 Turn back the labrum and the labium, and find just beneath 

 the labrum a pair of toothed, horny mandibles. Beneath- 

 these find another pair of jaws, also working horizontally 

 (the maxillce). Remove a maxilla entire, and examine it, 

 first with a lens, and afterward with low power of the 

 microscope. Note that it is a compound organ, made up of 

 a two-jointed basal portion bearing two terminal append- 

 ages. The inner appendage is the cutting or chewing part 

 of the maxilla (the lacinia, or blade); the other append- 

 age, standing behind or beside the lacinia, is the palpus. 



