Research on the mosquitoes of Angola - Systematic Catalog of ...

RIBgIRO, H. & RAMOS, H. Cunha -- <strong>Research</strong> on the mosquitoes of Angola -- X
DV/D ratio (64), SO, seems to be usually negative, this being the case
for all the apparently undistorted mounts measured by the writers fol-
lowing Barr's method (65).
In all pipiens females associated with males, the ratio of the length
of the upper fork cell to that of its stem ranged from 3.9 to 5.0 (mean
4.4). This ratio was shown to be a satisfactory criterium for separating
the females of the two forms () of the piplens complex thought to occur
in Angola. The scaling of the venter, giving less constant results, was
abandoned.
The larvae associated with pipiens males were also examined in
search for reliable morphological diagnostic characters, according to the
suggestions given by Knight (67). The subdorsal abdominal hair of
segments hi-IV was always double in our piplens larvae. However, as
this hair was also often branched in the larvae associated with quinquefasciatus
males, this character was abandoned as it is not diagnostic. In
that concerns the siphon index, it is clear that in the Angolan material
the highest values correspond to pipiens s. str. The usual marked variation
of this index, however, makes it a non-reliable diagnostic character,
much overlap being observed. The same is true, and even in a greater
extent, in that concerns the length of the anal papillae or the number
of the pecten teeth, though this one is usually smaller in pipiens. As
to the shape of the larval siphon, the sigmoidal curvature is often
marked in pipiens, but it is usually too an elusive character to be relied
upon.
The only valuable diagnostic character in Angolan larvae was found
in the branching of the siphonal tufts. The investigation of this character
was also suggested by Knight, though being presented as one > (op. cit.). After the examination of many
thousands of pipiens and quinquefasciatus larvae, it became obvious to
the writers that the last form has a greater branching of the siphonal
tufts than has pipiens. However, this character is of diagnostic value
only if one ignores the distal tufts (the branching of which does not differ
significantly in both forms) and takes into account only the two most
(D The term is used in the sense of Knight & Malek (66) and others,
that is, to designate each of the components of the (pipiens) complex regardless
of its questionable taxonomic status.
90 E.vtud., Ens. e l)oc.- 134