a handbook of the mosquitoes of north america - Systematic Catalog ...

CHARACTERISTICS 23
The eighth segment is short and bears on its dorsal aspect
the prominent respiratory tube or sipholz. On each side is
borne a prominent patch of scales-the comb (Fig. 9, C).
In this species the comb consists of a triangular group of from
20 to 30 small scales arranged in rows. Behind the comb are
two large feathered hair tufts and on each side of these a
single hair. The siphon is heavily chitinized, cylindrical, and
tapers gradually beyond the middle. On its basal half there
are two ventro-lateral longitudinal rows of closely set dentate,
flattened spines-the pecten. Beyond the pecten, near the mid-
dle of the siphon, are two laterally placed hair tufts. At its
tip we find the opening through which the larva takes air into
its tracheal system. This opening is closed by a series of five,
pointed flaps. When the larva comes to the surface the pointed
tips of the flaps penetrate the surface film and then spread out
and press against it. By this means the larva hangs suspended
from the surface and draws air into the tracheae.
The ninth segment is attached ventro-posteriorly to the
eighth segment and points directly downwards and backwards.
Its integument is chitinized on the dorsal and later surfaces,
forming the so-called dorsal plate. In this species the lateral
margins of the dorsal plate do not meet. on the ventral line.
In many species the dorsal plate forms a complete chitinous
ring and the ninth segment is then spoken of as “ringed by
the dorsal plate.” On the posterior-lateral margin of the
plate there is a single hair. Beyond the chitinous plate the
segment is fleshy and bears the anal opening. Surrounding
the anus are four cylindrical, tapering appendages, the tracheal
or aflu1 gills. At the postero-dorsal angle is located the dor-
sal brush. In this. species this consists of a short multiple hair
tuft and a long stiff hair on each side of the median line. These
are inserted on small chitinous bases. On the ventro-pos-
terior margin is located the remarkable group of hair tufts
known as the rdentral brush. Compare this larva with that of
Anopheles pwctipenzis shown in Figure 9A.