534 HEMIPTERA CHAP. 



injuries really due to Hemiptera are frequently attributed to 

 other causes. 



In the course of the following brief sketch of the anatomy 

 and development of Hemiptera, we shall frequently have to use 

 the terms Heteroptera and Homoptera ; we may therefore here 

 mention that there are two great divisions of Hemiptera having 

 but little connection, and known by the above names : the 

 members of these two Sub-Orders may in most cases be dis- 

 tinguished by the condition of the wings, as mentioned in the 

 definition at the commencement of this chapter. 



External structure. The mouth-parts consist of an anterior 

 or upper and a posterior or lower enwrapping part, and of the 

 organs proper, which are four hair-like bodies, dilated at their 

 bases and resting on a complex chitinous framework. The 

 lower part forms by far the larger portion of the sheath and is of 

 very diverse lengths, and from one to four-jointed : it is as it were 

 an enwrapping organ, and a groove may be seen running along it, 

 in addition to the evident cross - segmentation. The upper 

 covering part is much smaller, and only fills a gap at the base 

 of the sheath ; it can readily be lifted so as to disclose the setae ; 

 these latter organs are fine, flexible, closely connected, rods, four 

 in number, though often seeming to be only three, owing to the 

 intimate union of the components of one of the two pairs ; at 

 their base the setae become broader, and are closely connected 

 with some of the loops of the chitinous framework that is con- 

 tained within the head. Sometimes the setae are much longer 

 than the sheath ; they are capable of protrusion. Although 

 varying considerably in minor points, such as the lengths of the 

 sheath and setae, and the number of cross-joints of the sheath, 

 these structures are so far as is known constant throughout the 

 Order. There are no palpi, and the only additions exceptionally 

 present are a pair of small plates that in certain forms (aquatic 

 family Belostomidae) lie on the front of the proboscis near the 

 tip, overlapping, in fact, the last of the cross-articulations. 



Simple as is this system of trophi its morphology is uncertain, 

 and has given rise to much difference of interpretation. It may 

 be granted that the two portions of the sheath are respectively 

 upper lip, and labium ; but as to the other parts wide difference 

 of opinion still prevails. On the whole the view most generally 

 accepted, to the effect that the inner pair of the setae correspond 



