MAXnj.ARY PALPI 51 



the number of the joints. They show great diversity in the different genera and 

 in the species. They differ greatly in length, in shape, and in the number of 

 joints. The relative length of the palpi, without reference to the number of 

 joints, has been generally considered as a character of primary importance in 

 classification. Beyond that there has been general disagreement as to the 

 number of component joints. Dimmock, whom we have quoted, considered 

 the palpi of Culex pipiens as four-jointed in the female, five-jointed in the male. 

 Meinert states for the same species, three-jointed in the female, four-jointed in 

 the male. Both these authors found that in other species a small additional 

 joint was present in the females. Ficalbi considered that in Culex the palpi of 

 the female are three to four-jointed, those of the male three- jointed. Wesche 

 considered the palpi four-jointed in both sexes. Felt states that in most 

 Culicidae the palpi are five-jointed in both sexes, except in certain females " when 

 the rudimentary fifth appears to be wanting." Theobald, in Genera Insectorum, 

 states that the palpi of the Culicidae have from one to six joints. 



The idea that the number of joints in the palpi is constant within groups and 

 of great classificatory importance has been very generally accepted. The state- 

 ment that the palpi of the Nemocera are four or five-jointed, which originated 

 with Latreille (1809), has been widely followed with but little modification. 

 Becher considered the palpi of the Nemocera four-jointed and called the basal 

 part " Tasterschuppe," the equivalent of the palpifer, or, in its absence, of the 

 maxillary stipes. Williston, in the introduction to his Manual of North Ameri- 

 can Diptera (third edition, 1908, page 26), states of the palpi of the Diptera: 



" Perhaps the most important of all the mouth-parts, from the systematic 

 standpoint, are the maxillary palpi. . . . They are variously described as being 

 composed of from one to five joints. There are never more than four articulated 

 joints, the basal joint being merely a process of the plate bearing the maxillae. 

 The tendency in diptera is toward their entire loss, and in the more highly 

 specialized families there is never more than one joint." 



Farther on (p. 65) he says of the Nemocera: "Palpi usually more or less 

 elongate, composed of from one to five, usually four, joints, rarely absent." 

 While there is undoubtedly a reduction in the palpi parallel ^vith specialization, 

 this reduction has taken place independently at different points, and, except in 

 a very broad way, the palpi can not in themselves be considered as a safe index 

 of relationships. The ideas of systematists have been based largely upon the 

 study of a few typical forms, and no attempt appears to have been made to test 

 their constancy within a family. In fact, within the Culicidge the palpi may be 

 said to be remarkably unstable in character. They range all the way from forms 

 with several well-defined joints, as Anopheles, to forms in which they are re- 

 duced to a small club-shaped organ without trace of jointing. In fact, the 

 homologizing of the palpal joints of the different forms, which Felt attempted to 

 carry out, assuming five joints for the more generalized forms, is beset with pe- 

 culiar difficulties. The conditions in the basal portion of the organ, which have 

 generally been considered as true joints, are not clearly defined or sufficiently, 

 uniform within the group to be so interpreted. We have not found any mos- 



