LIBRARY

Naiad Adult
Elongate and campodeiform. Elongate and somewhat flattened or cylindrical.
Head large with two compound eyes and Head small, compound eyes always presthree
ocelli. ent, larger and often divided in the
rnale, the front portion being raised or
pillared and known as turban-eyed.
With three ocelli.
Antennre usually quite long, filiform and Antennre usually short, composed of two
many segmented. basal segments and an indistinctly
jointed apical portion.
Mouth parts well developed, with labrum, Mouth parts aborted or at most very
strong mandibles, three-segmented max- weakly developed; mandibles vestigial
illary palpi, quadrifid labium, three-seg- ar absent, maxillre very small, but with
mented labial palpi, and conspicuous palpi present.
maxiJIulre associated with the hypopharynx.
Mandibles of a very primitive type.
Thoracic segments large, pro thorax narrow- Thoracic segments well developed with
est. the mesothorax much larger than the
other segments.
Legs shorter and stouter than in the adults, Legs variable, fore pair greatly elongated
one-segmented tarsi with single claw. in some males to aid mating, one- to
five-segmented tarsi (usually four to
five) with two simple or bifid claws.
Apterous or with wing pads. Apterous or generally with two unequal
pairs of many-veined. fragile wings,
of which the fore pair is much the
larger and the hind pair often very
small or even wanting.
Abdomen obviously lO-segmented, the 11th
segment assuming the form of a manysegmented
median filament as long as or
shorter than the cerci. The median filament
may not appear in the first stage
young.
Abdomen obviously lO-segmented, the
11th segment in the form of a reduced
tergum or a greatly elongated, multi-
segmented appendage similar in form
and length to the cerci. The male
genitalia consist of a pair of simple incurved
claspers and two penes, each
with a separate opening. The oviducts
of the female open between stemites
7 and 8. .
Cerci rather short or long and slender,
many-segmented and often with conspicuous
fringes.
Respiration by external gills upon some or
all of the first seven abdominal segments
Cerci long, filiform, multi-segmented, and
shorter or longer than the body.
-
Respiration spiracuJar through two pairs
of thoracic and eight pairs of abdom-
extending from the dorsum or sides. Gills
variable in size and fOml, but often leaflike
in appearance. No other insects have
gills so si tua ted.
215
inal spiracles.