64 
MALARIA 
special note are the frontal head hairs, 
which consist of three pairs, usually large 
and plumose, placed in a straight line 
across the middle of the head capsule, or 
frontoelypeus. Large plumose lateral hairs 
occur on the thoracic segments and on the 
first three abdominal segments. Toward 
the front of the head there are three pairs 
of so-called clypeal hairs, the two anterior 
pairs especially being used extensively in 
identification. On the ventral side of the 
thorax are three paired groups, known as 
the pleural hairs, the points of origin of 
which correspond to structures found on 
other dipterous larvae and are believed to 
be the remains of larval legs in this order. 
The character of these hairs tends to he 
correlated with other characters that differ¬ 
entiate subgenera and other species groups. 
A system of numbers has been developed 
for all the hairs of the fourth instar and is 
convenient for taxonomic work. Perhaps 
the most complete of the several lists pub¬ 
lished is that of Puri (1931). 
In the younger instars a broad collar of 
dark chitin is present at the base of the 
head, decreasing in comparative width with 
each succeeding molt. This collar is useful 
in distinguishing fourth-instars from ear¬ 
lier stages. Third-instars, so far as known, 
have the same number of hairs as in the 
fourth instar but the number of branches 
of the branched hairs is usually less. A 
detailed study of the pilotaxy of the differ¬ 
ent instars of Anopheles walkeri has been 
presented by Hurlbut (1938a). He states 
that the definitive form and position of the 
hairs are already evident in the second 
instar but that certain hairs are lacking 
and the number of branches of other hairs 
is still further reduced. In the first instar 
he finds that many of the hairs differ strik¬ 
ingly in form and position from those in 
the next instar. This author has also made 
a study of the early instars of other species 
and has prepared a key (in press) for the 
identification of first-instars of the com¬ 
mon Southern species. 
In the pupa of anophelines the air trum¬ 
pets invariably have a short base and a 
wide opening, usually decidedly flared in 
appearance. This has proved to be a very 
useful character for recognizing Anopheles 
pupae in field collecting. There is also a 
stout, black spine on the posterior corners 
of abdominal segments 3 to 7, while the 
eighth segment has a similar stout spine 
usually with plumose lateral branches. 
Edwards (1932) separates the pupae of 
this tribe by the fact that the apical lateral 
hair of the abdominal segments is placed at 
the corner of the segments, whereas it is 
well away from the corner in other mos¬ 
quitoes. As a rule, the number of branches 
of the pupal hairs is subject to considerable 
variation, but specific differences have been 
found in some cases. The pupal characters, 
however, do not appear to be'of mueh value 
for the separation of higher groups. 
The eggs of anophelines are boat-shaped 
in outline and their most distinctive fea¬ 
ture is the presence of floats, or hydrostatic 
organs, on each side. These floats are di¬ 
vided into a number of small compart¬ 
ments, filled with air. The surface of the 
egg is finely reticulated and the outer mem¬ 
brane, or exochorion, on the dorsal surface 
varies considerably in pattern. The egg 
characters, principally those of the floats 
and dorsal pattern, have been studied ex¬ 
tensively in recent years and have been em¬ 
ployed for the separation of closely related 
species and subspecies, particularly those 
of the maculipennis group. 
Classification 
The anophelines of the world are divided 
by Edwards (1932) into three genera— 
Anopheles, Chagasia, and Bironella; and 
the genus Anopheles into four subgenera— 
Anopheles, Myzomyia, Nyssorhynchus, and 
Stethomyia. Dyar (1928) recognized only 
the single genus Anopheles in the Amer¬ 
icas, with Anopheles, Chagasia, Kerteszia, 
and Nyssorhynchus as subgen'era ( Biron¬ 
ella and Myzomyia being limited to the 
Old World). Except for Anopheles albi- 
manus, which is found in the lower Rio 
Grande Valley, all the anophelines of the 
United States and Canada belong to the 
subgenus Anopheles and also to the group 
Anopheles as defined by Edwards. 
