28 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [Bull. 



through which the liquid is drawn, often containing needle-like 

 organs called lancets for puncturing the tissues. The proboscis 

 is formed by a modification of either the labium or the maxillae. 

 The structure of the mouth-parts is of great importance, 

 not only in classification but also in practical work with insects, 

 as the application of insecticides depends upon the structure of 

 the mouth-parts. 



Thorax. 



The thorax is made up of three ring-like segments known 

 respectively as pro-, meso-, and metathorax, and bears the 

 organs of locomotion. Wings, when present, are borne dorsally 

 by the meso- and metathorax, but one or both pairs may be 

 absent. Flies have only the first pair of wings fitted for flight, 

 the second pair being represented by a pair of knobbed threads, 

 called halteres or balancers, the function of which is not well 

 understood. In earwigs and beetles a pair of veinless horny 

 wing covers takes the place of the first pair of wings. Grass- 

 hoppers, crickets, and locusts have a pair of closely veined, 

 leathery fore wings which are used in flight. 



The veins or nerves of the wings are designated by letters 

 and numbers. The spaces between the veins are called cells, 

 and are similarly designated. Wings of butterflies and moths 

 are covered with scales, which give them their color patterns. 

 Each segment of the thorax bears ventrally a pair of jointed 

 legs ; each leg consists of coxa, trochanter, femur, tibia, and 

 tarsus. The tarsus is often many jointed and terminates in a 

 claw. 



Abdomen. 



The abdomen bears the organs of reproduction, and is made 

 up of simple and distinct ring-like segments, varying in the 

 different insects from three to nine in number. In the lowest 

 order of insects, Thysanura, are found some forms with ab- 

 dominal legs, but in no other adult insects are locomotive organs 

 attached to the abdomen. In caterpillars and other larval forms 

 fleshy appendages known as prolegs or false legs are borne upon 

 the ventral surface of the abdomen. 



The apex or distal extremity of the abdomen is furnished 

 with various appendages in the different families of insects, such 



