( S61 ) 



closely behind the mid coxae. The luptasternnm is anteriorly nearly as wide as the 

 mesosternnm is posteriorly, and is strongly ronnded, being much broader than long. 

 From underneath this sclerite projects an obtuse intercoxal process, the meso- 

 sternnm overlapping the bases of the bind coxae. The process is hollow underneath, 

 being a kind of half-cylinder. The remaining species conform in these sclerites to 

 PI. Xlll. fig. 0, apart from the mesosternnm being much longer in some species than 

 in the form represented by our figure 6. In these species the metasternum (central 

 sclerite) is reduced to a sclerite corresponding to the intercoxal process of text- 

 fig. 2, there being no transverse suture immediately behind the mid coxae. 



Text-fig. 2. 



The sterna are tlat centrally and more or less strongly slanting laterally, 

 the sides forming usually a distinct angle with the central plane. The deeply 

 hollow sides of the prosternite serve as a retreat for the modified fore legs, and 

 have no hairs. 



The legs, which are long and more primitive in the American forms and short 

 and more specialised in all the Old- World species, are difterent to some extent 

 in every species, distinctions ohtaiuing in the mimber, size and position of the 

 bristles, the number of psendo-joiiits in the tibiae and in the structure of the 

 tarsi. Speiser, in demonstrating the fairly close agreement between the Pohjctems 

 tarsus and that of Cimex, came to the conclusion that the tarsus of I'olt/ctenes 

 consists of three segments, of which the second is divided by a pseudo-joiut. We 

 agree with this conclusion. Although the pseudo-joiut is sometimes very distinct, 

 it is never so well defined as the joints between ihe true segments. In several 

 cases the jiseudo-joint is hardly indicated (PI. XIII. tig. 7, XIV. tig. 13). The tarsi 

 of the immature specimens, as must be expected, have a segment less than the 

 adults, the end-segment being long and undivided (PI. XIII. tig. 8), the division 

 taking place a short distauce beyond the first segment in or near the spot where 

 the pseudo-joint of the adult is situated. 



The claws vary from being nearly alike, as in the American Polycteuids, 

 to being very asymmetrical (PI. XIII. tig. 7). It is always the inner claw which 

 becomes reduced, the outer claw at the same time being enlarged. The inner 

 claw is the one on the side nearest the body. As the body is broad aud flat, 

 the mid aud hind legs as a rule stretch out sideways, the femur aud tibia forming 



37 



