14 



GUIDE TO CALIFORNIA INSECTS 



is attached to the inner end of the wing root and extends toward the breast. 

 The down stroke of the wing results from the contraction of muscles attached 

 to the side below the wing hinge which simply pull the sides in, forcing the 

 blood against the back and wing roots elevating them and so depressing the 

 wing. 



'yV\exo-thorax 



Mela-fhoi-aji 



Ji^AU.Seg. 



Figure 9. Diagram of thoracic structure rtotted lines showing infoldings for stif- 

 fening the segment. Letters as shown in figure 8. 



Figure 10. Diagram of wing fold. F. fold area. 



In the great majority of insects on the contrary the middle of the back 

 is bent up by the pull of muscles extending lengthwise and the up stroke by 

 muscles reaching from back to breast. 



The full name of an insect consists of: — 



1. Genus name, usually a Greek substantive and always beginning with a 



