TAKSAL STRUCTURES 63 



The front tibise are often the longest in the Sabethini. At their apices the tibiae 

 are more or less excavate behind and bear several stout spines, and in addition, 

 particularly on the front and hind pair, numerous stiff setae. Upon the front 

 and hind tibise these setae are densely massed upon the broader portions of the 

 tibiae and in addition there is, subapically on the inner side, a transverse row of 

 very densely placed setae. Below this row of setae are usually present several 

 slender spines, also in a transverse row. These spines have been termed the 

 tibial scraper and their presence or absence, on the hind tibiae, and their number, 

 are of systematic value. The tibiae also bear longitudinal series of spines and 

 these differ in character with the species. 



The tarsi are slender, cylindrical and differ considerably in their proportions 

 on the three pairs of legs. They are, as a whole, much longer on the hind legs 

 and it is they largely that determine the predominating length of this pair of 

 legs. The first tarsal joint is always very long in all three pairs of legs, although 

 usually somewhat shorter than the tibia. In Anopheles, however, the first tarsal 

 joint of the hind legs is longer than the tibia. The first tarsal joint is by many 

 systematists called the " metatarsus."' The application of this term is incorrect 

 as it implies something beyond, or outward, from the tarsus. As the first tarsals 

 differ from the following ones only in length, and this is not true of all Diptera, 

 there is no reason why they should be designated by a special term. Further- 

 more the introduction of this term has brought about much confusion in de- 

 scriptive work ; when an author has been inconsistent in this usage it is some- 

 times impossible to determine if his " first joint " is in reality the first or the 

 second. 



Each tarsal joint is shorter than the one preceding it; the only interruption 

 occurs, sometimes, in the last two tarsals of the front and middle legs, the fourth 

 joint being in such case the shorter. This progressive reduction is most rapid 

 on the front and middle legs, the hind tarsi are always much the longest. In 

 many forms the front tarsi are, as a whole, noticeably shorter than the middle 

 ones, while still more often they are nearly equal. In some Sabethini the middle 

 tarsi are shorter than the anterior ones. 



The fourth tarsal joint, as already indicated, is often shorter than the fifth, 

 either upon both the front and middle legs or upon the front legs alone. This 

 difference is greatest in those males in which the claws show the most sexual 

 modification. In the female the fourth joint, if shorter than the fifth, is usually 

 but slightly so ; in Bancroftia, however, the fourth joint is very short, about as 

 long as broad. In the females of Anopheles and in both sexes of most Sabethini 

 the last tarsal joint is distinctly the shortest. All the tarsal joints but the last 

 bear a pair of spurs apically beneath. In addition there are longitudinal series 

 of spines or setae ; these, and the terminal spurs, are variously developed in the 

 different genera and species. The last tarsal joint bears the two claws, or, in a 

 few cases, a single claw. In the females, and in many males, the fifth tarsal 

 joint is cylindrical, resembling in character the other joints. It is often ob- 

 liquely excised at the tip beneath for the insertion of the claws and their mechan- 

 ism. In the males of most Culicini, and in the male of Joblotia, the fifth tarsal 



