Biology of the Membra cidae of the Cayuga Lake Basin 339 



This description applies pretty generally to the tibiae of all the species 

 in the subfamily Membracinae, and very few generic or specific structural 

 characters have been noted. The legs are usually so placed when the insect 

 is at rest in a natural position that the broad, flat, lateral faces of the 

 tibiae completely hide all other parts of the legs and most of the ventral 

 thorax. From a cephalic view (Plate xxxvi, 4-6) the tibiae appear less 

 flattened, and in those that are spined only one row of spines is seen. 



It has already been noted that foliaceous tibiae occur in species widely 

 removed from the Membracinae. These are commonest in certain genera 

 of the subfamily Centrotinae. In this group the tibiae are often even more 

 leaflike than in the type genus described above, and more striking in 

 appearance. One noticeable difference, however, is the fact that in the 

 Centrotinae all three pairs of tibiae are foliaceous (Plate xxxvi, 7-9), 

 and the hind pair are often as broad as either of the two preceding pairs. 

 In these forms the hind tibia is seldom spurred, but all three pairs are 

 inclined to develop short, stiff hairs along the margins. In cross section 

 also a difference is noted (Plate xxxvi, 13-15), in that the segments seem 

 to be developed from a central rod with the margins appearing as lateral 

 expansions. This condition is most noticeable in the posterior tibia, 

 in which the central rod has a decided midrib appearance (Plate xxxvi, 

 15). These characters are quite sufficient to distinguish most of the 

 species of the Centrotinae which show the foliaceous type of leg. 



In by far the larger number of forms of the family the tibia is round, 

 oval, or triangular in cross section (Plate xxxvi, 16-18) and uniform in 

 diameter (Plate xxxv, 1-5). In the non-foliaceous type of tibia the first 

 and second pairs are most likely to be rounded while the posterior pair 

 usually shows the three-cornered shape. In the latter form one angle 

 points directly cephalad while the other two angles project latero-caudad 

 to the right and left, leaving a flat posterior face. All three angles bear 

 spines or hairs. It should be remembered in interpreting these terms that 

 in the normal position the hind leg of the insect projects almost directly 

 backward from the body, the coxa extending more or less meso-laterad, 

 the trochanter latero-ventrad, the femur dorso-caudad, and the tibia 

 ventro-caudad. 



The tibiae show color patterns and various markings when the legs 

 are at all decorated. These segments also are usually pubescent, or hairy, 

 and the extremities generally show one or more rings of spines or bristles 



