KEY TO THE ORDERS OF INSECTS 



1a Insects with wings 



1b Insects having no wings or only rudimentary wings 



2 



17 



2a Insects with only one pair of thin, usually transparent 

 wings, second pair replaced with short, pin-like structures. 

 (Flies, mosquitoes etc.) Figs. 33 and 200 to 225. 



Order XXI I I, DIPTERA p. 97 



Fig. o3. A Fly Musca domestlca L. 



The Conur^on House-fly. Dull blackish 

 gray. Incidental carrier of several 

 diseases and a general pest. Length 

 6-8 mm., (from U.S.D.A. ) 



The Dlptera are the True Files. They 

 never have more than one pair of wings. 

 Instead of a second pair they have 

 knobbed structures known as balancers or 

 halteres. Their young are usually leg- 

 less and are called "wrigglers," "mag- 

 gots" or "bots." The order Is not well 

 known. It would seem that It may prove 

 as large as the Coleoptera when thor- 

 Figure 33. oughly worked. 



2b 



Insects with two pairs of wings* 3 



3a The two pairs of wings unlike in structure *{not equal in 

 thickness or transparency) as in the beetles, true bugs, grass- 

 hoppers. Figs. 34, 90, 156, etc 4 



Figure ?-i. 



*NOTE — The front wings of beetles (Coleoptera) 

 are thick and hard and meet in a straight line 

 down the back. The front v.-ings of the true 

 bugs (Hemiptera) are thick and hard at the 

 base and membraneous at the tips. These tips 

 overlap. In considering specimens of either 

 of these orders a second pair of membraneous 

 wings may be taken for granted, since parts 

 of dried specimens should not be touched or 

 moved. 



Fig. 34. A Cockroach. Blatella germ:inlca L. 



The Croton Bug. Yellowish brown with 

 dark brown markings. Length 10-15 mm. 



3b Both pairs of wings of similar structure (having about the 

 same degree of thickness and transparency as in the bees, 

 butterflies, dragon flies, etc.) Figs. 35, 67, 165, 179 etc. 



37 



