16 



HETEROPTERA OF EASTERN NORTH AMERICA. 



along the lower part of the body and between the coxae. It 

 consists of two parts (fig. 2), a sheath or tube-like outer part 

 of horn-like chitinous texture and an inner sucking organ 

 proper composed of four very slender hair-like setae which are 

 somewhat dilated at the base. The sheath consists of an elon- 

 gated grooved lithium or lower portion which is divided into 



segments or joints of variable 

 length and one to four in num- 

 ber, and a short upper flexible 

 portion covering the base of the 

 setae and corresponding to the 

 labium of other insects. The 

 sheath serves as a wrap or pro- 

 tection for the delicate setae, 

 and also, in some of the pre- 

 daceous Heteroptera, as a pierc- 

 ing or defensive organ. The 

 setae are fine flexible rods 

 which can be fitted closely to- 

 gether to form a tube. They 

 vary in length, sometimes be- 

 ing much longer than the 

 sheath and are capable of pro- 

 trusion. Their tips are very 

 sharp and for the most part 

 make almost invisible pricks in the epidermis of leaf or larvae 

 of insects. Usually they alone are used in piercing the object 

 used as food. The outer pair are generally barbed near the 

 tips and when inserted in a victim readily maintain their hold. 

 Sometimes the struggles of the prey pull the setae out of and 

 to one side of the sheath. The bug then releases its hold and 

 draws the beak between the front tarsi, in the same manner 

 that an ant cleans its antennae, thus forcing the setae back 

 within the sheath. The relative length of the beak and of its 

 segments are much used in the classification of the Heterop- 

 tera. 



The antennae of a bug are usually inserted in shallow cavities 

 on the front or sides of the head and articulate with the latter 

 by a ball and socket joint. In the aquatic forms they are 

 shorter than the head and are generally concealed in small 

 pockets or cavities on the under side of the head. They 

 are usually composed of only four or five segments which vary 



Fig. 2. Beak of Nezara viridula (L.). 

 A, dorsal view with setae pulled out from 

 sheath ; B, same with setae in normal 

 position within sheath ; 7, labrum ; H, 

 labium: m , mandible: mx, maxillae; s, 

 setae within sheath, their tips protrud- 

 ing; C. tip of mandible greatly enlarged, 

 showing barbed tip. (After Drake). 



