REDUCTION OF PALPI 53 
with the maxillary palpi, it is different when the palpi consist of only two, or 
even of a single joint, as is the rule in the Diptera, for there will then be no 
joint left to explain as maxillary palpus. I therefore prefer to regard the palpi 
of the Diptera as homologous with the entire maxille of other insects, only that 
they are oftenest unjointed and not divided into different components. Only in 
Simulium, Tipula, and Limmobia I have thought to find an indication, in the 
before mentioned appendix at the base of the palpi, of the different working 
divisions of the exponents of the second metamere of other insects.” 
The palpi are variously modified in the different forms. In Anopheles and in 
the males of a great many other forms the palpi about equal the proboscis in 
length, or even exceed it. In most of these forms the palpi are slender, particu- 
larly in their proximal halves, and furnished with false joints to increase their 
flexibility so that they can be folded back when the insects are feeding. 
In Megarhinus, however, where the palpi are less in the way, on account of the 
downward-curved proboscis, they are stout and quite rigid, without basal false 
joints, and the joints are armed near their apices with heavy spines. In the 
males of Anopheles and of most species of Culiseta the palpi are enlarged 
apically into a distinct club. In Anopheles the club is composed of the outer 
two joints, while in Culiseta it may be composed of these same two joints or of 
the last joint alone. 
In the males with long palpi of many species of Culex and Aédes the outer 
half of the palpi is more or less thickened and densely hairy, the last joint, how- 
ever, generally tapering to a point; the last two joints are usually curved upward. 
In Megarhinus and Bancroftia we begin to get a reduction in the female palpi, 
and this occurs principally in the terminal joint. In the American species of 
Megarhinus the palpi of the female are about two-thirds the length of the pro- 
boscis, while in the Old World species of this genus the reduction has gone still 
farther and they are sometimes less than one-fourth the length of the proboscis. 
In the females of both the New and the Old World species of Megarhinus there 
is a minute terminal joint, and the number of joints is the same. 
In Bancroftia the palpi of the female are about two-fifths the length of the 
proboscis, the terminal joint small; in the case of one species (B. fascipes) the 
terminal joint is about three times as long as wide, in another (B. signifer) it is 
nearly globose. In the male of this last-named species, although the palpi are 
as long as the proboscis, the last joint is similar in character to that of the 
female. 
In the males of most species of Aédes and of Culex the palpi are longer than 
the proboscis, curved upward, their outer halves densely hairy, the last joint 
long and tapering. In certain species of Aédes the palpi of the male are slightly 
shorter than the proboscis, straight, less hairy, the last joint long but blunt at 
the tip. In Aédes fuscus the palpi of the male are very short, in fact shorter 
than those of the female, and the terminal joint is indicated by a flattened 
tubercle. In the related genus Stegoconops the reduction of the male palpi has. 
become more general. In S. equinus the palpi of the male are about three- 
fourths the length of the proboscis ; in S. albomaculatus the palpi are practically 
alike in the two sexes, short and with a minute terminal joint. 
5 
