24 



GENERAL BIOLOGY 



How to know the orders 

 of flower insects. — But five 

 orders'"'' of insects are com- 

 monly found upon flowers. 

 The membersof these orders 

 may readily be recognized 

 by the following single 

 distinctive characters : 



The Diptera alone have 

 but two wings. 



The Lepidoptera alone 

 have the wrings covered 

 with dust-like scales that 

 rub off between the thumb 

 and finger: likewise, a 

 coiled proboscis. 

 The Coleoptera alone have the fore wings {elytra) meet- 

 ing in a straight line down the middle of the back, not over- 

 lapping. 



The Hemiptera alone have a jointed proboscis directed 

 backward between the fore legs. 



The Hymenoptera alone have a sting; likewise, they 

 lack all the preceding characters: the small hind wings 

 being usually attached to the margin of the fore wings by a 

 series of hooklets, the beginner may overlook them at first. 



Study 2. Insects adapted to visiting flowers. 



Apparatus needed: A cyanide bottle, an air net and a 

 lens. 



Materials needed: Ten or more species of insects, to be 

 gathered from flowers by the student, who should observe 



Fig. 20 Butterfly {Colias philodice) on 

 a clover head. 



*Omitting from consideration the minute but ever present thrips 

 (order Physopoda) found hidden within the flowers — insects usually 

 less than a millimeter long, with straight bodies and veinless wings, 

 of slight importance in this connection. 



