External Structure of a Mosquito. 7 
united laterally by the soft spiracular membrane, in which the 
air-holes are placed. The last two segments have the genital 
and anal openings. The anus is on the venter of the eighth seg¬ 
ment ; the genital opening on the ninth; the upper part of the 
latter (the tergum) is often hidden in the eighth segment. 
The genitalia are attached to the ninth segment, and consist 
of two various-shaped lobed appendages in both sexes, but in 
the male the basal lobes are provided at their apex with a 
clasper (Fig. 7, IV.), whilst in the 9 they end in a bristly 
extremity. The genitalia are of specific importance. The 
first abdominal segment is of some service in identifying species, 
and is provided with flat scales ( Culex , &c.) in various positions, 
and is always densely hairy. 
The wings of the Culicidae have the veins clothed with scales 
which vary in different groups ; the typical venation is given on 
page 18. The halteres (Fig. 7, V. H) have the knob mostly 
cup-shaped and scaled, and present so few characteristics that 
no further reference need be made to them. 
The leg of Culex consists of a small coxa and trochanter at 
the base, the former often with a patch of scales ; the femur 
and tibia, which are usually much about the same width and 
length and offer but few specific characters, although in a few 
cases the femur becomes much enlarged (Anopheles and TJra- 
notaemd) ; the tibia is followed by the metatarsus , sometimes 
called the first tarsal joint ; the metatarsus, which is the term I 
have adopted for the long joint following the tibia, is of specific 
value in regard to its proportionate length with the tibia in 
some species in the hind legs; the true tarsus , or foot, consists of 
four joints, which usually decrease to the apex, but which are often 
modified in other ways, especially in the male. The ungues are 
hooked claws at the end of the last tarsal joint ; they may be 
equal and simple in the 9 > or may have a single tooth ; in the 
£ those of the fore and mid legs are usually unequal and toothed 
in various ways ; the hind are small and equal, and are usually 
simple. After studying a number of types, I have come to the 
conclusion they are of great specific value, but not of generic 
value, hence genera based largely on their structure have been 
omitted; when untoothed they are spoken of as simple, when 
single-toothed uniserrated, and when with two teeth, biserrated ; 
in a few cases triserrated ungues exist. In connection with the 
ungues there also exist in a variety of forms the pulvilli and a 
plumose empodium. 
