26 HOMOPTERA 



The tibia has attracted more attention in the Membracida than any other segment of the leg. This 

 is because in certain forms of the family this segmeiit is broadly fohaceous and very striking in appear- 

 ance. On the basis of this peculiarity the genus Membracis, the type genus of the family, was early 

 separated (Fabricius lyyS), and the character has since stood as the distinguishing mark of the subf. 

 Membracitta, which has been built up around this genus. The character in itself, however, is not sufh- 

 cient to distinguish the subfamily, since a number of genera of the subf. Cefitrotitta show the same flatten- 

 ed, leaf-hke tibiae. It is only vahd when considered in connection with the covered scutellum. The 

 foHaceous tibia as represented in the Mentbracinie, however, shows a decided variation in the three pairs 

 of legs; in the lirst and second pairs the tibiag are broadly foliaceous, often three times as wide as the 

 femur, and generally smooth and without spines or bristles, while in the posterior pair of legs the tibias 

 are proportionally much narrower and less leaf-hke, and are usually armed with strong teeth or spines. 

 In the Centrotince, on the other hand, the fohaceous forms show all three pairs of tibise equally expanded, 

 the hind pair often as broad as either of the two preceding pairs, and the hind tibia shows a strong 

 central rod or mid-rib which is quite characteristic of the subfamily. The tibiae show color patterns 

 and various maikings when the legs are at all decorated and the segments are usually pubescent or hairy. 



The tarsus is trimerous and comparatively uniform throughout the family . Of the three segments 

 the middle one is usually the shortest; the first and last vary with the leg, the first being the longest 

 in the hind legand the last being the longest in the first two pairs of legs. Each segment is somewhat 

 club-shaped, narrower at its proximal and swoUen at its distal end. At the distal ends the segments are 

 not evenly truncate but are much extended on the underside and bilobed above. Each tarsus bears 

 astrong claw, distinctly articulated with the last segment. Each claw is heavy at its base and becomes 

 gradually acuminate to a fine, sharp point. No pulvillus is present, but most forms show a broad, 

 irregular membrane below each half of the claw. The claw is attached to the last tarsal segment by a 

 strong tendon, which is shghtly chitinized at its junction with the lower base of the claw and is conspic- 

 uous as a heavy cord. The comparative length of the tarsal segments varies considerably and this 

 feature may be used as a specific character but it is of doubtful value. Usually the segments increase 

 in length from in front backward, the hind tarsi being the longest. In most cases the first and second 

 pairs of legs show this difference only slightly, while the hind tarsi are easily seen to be much longer 

 than the others. A notable exception to this occurs in the subf. Platycotina, in which the hind tarsi are 

 very much shorter than the anterior or the intermediate ones. This is the character on which the forms 

 of this subfamily are separated and it is entirely reUable. The relative smallness of the posterior tarsi 

 in these forms is made more conspicuous because of the fact that the posterior tibiae are much swoUen 

 at their distal ends, making the comparison between the tibise and the tarsal segments all the more 

 noticeable. It is interesting to observe that when any tarsal variation occurs in the Membracida it 

 appears in the hind leg rather than in either of the others. The tarsi are much given to pubescence and 

 hairiness. In some species this development is so remarkable as to be used in diagnosis. In the subf- 

 Centrotina the bristles, spines and hairs are so numerous in many species as to completely hide the other 

 structural characters of the tarsus. Aside from its use as the distinguishing character of the subf. 

 Platycotina, the tarsus has been liltle used for systematic purposes in the study of the Membracida. 

 There is little doubt but that enough variation exists to warrant more careful consideration of this part 

 of the leg, and a further study of the hind tarsus may yield good taxonomic data. 



The Abdomen. — The abdomen consists normally of eleven segments, of which the first is 

 only partially developed and the last two are more or less modified. The arrangement and number 

 of segments is best shown in the nymph, in which the anal region is represented by a series of tele- 

 scoping tubes. In this stage the iirst segment is hidden under the metathoiax and the last is poorly 



