INSECTA. 31 



to the opinion that they must be regarded as out- 

 growths of the system of air-vessels, and of the 

 outer wall of the body, which have together formed 

 organs, varying from the sac-like pads to the fully 

 formed wings. Some authors, however, consider them 

 to be modified limbs which have been shifted in posi- 

 tion and altered in form and function. Whether this 

 be true or not, the teacher need not consider ; in 

 either case, they are membranous expansions of the 

 body wall, are developed from the thick pads of the 

 young, and their veins are hollow tubes (see p. 39). 



An artificial wing is needed to show the effects of 

 the resistance of the air upon the flight of insects. 

 One can be made of a bamboo rod and Holland cloth 

 which will answer the purpose fairly well. Select a 

 rod about forty-nine inches long, split the flexible tip 

 of the rod by sawing it through thirty inches, leaving 

 the remaining portion whole, to furnish a handle. The 

 spokes of a dismembered fan made of split bamboo 

 can then be placed in parallel fines about an inch 

 apart and glued to a long piece of cloth, and the top 

 side covered by a layer of thin cloth or tissue paper. 

 A wing similar in shape to that of a dragon-fly, but 

 straight on the forward side, can then be cut out of 

 this, but it should be not less than ten inches at the 

 broadest part. This cloth wing can be sewed or tied 

 into the sawed-out split of the bamboo rod with twine, 

 and is then ready for use. A wing might be made by 

 using a socket and longer strips of split bamboo, which 

 would more closely represent a wing with its network 

 of veins, but it is not essential to imitate nature very 

 closely in this instrument. The bamboo represents suf- 



