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Immature Stages
of Agriotypidae
Immature stages of Agriotypidae were discussed in
detail by Clausen (1940), as follows: The egg of Agriotypus gracilis Waterston measures 0.
9 mm. in length and 0. 18 mm. in
greatest width and is slightly larger than that of A. armatus. It is slightly convex dorsally and broadest
at the anterior end, and the posterior end is smoothly rounded. The chorion is exceedingly thick and
tough. At the anterior end is a heavy
pedicel of variable length, ranging up to 0.25 mm., the distal extremity of
which is irregularly expanded. This
"button" is embedded in the integument of the host and anchors the
egg firmly in position. Both pedicel
and button become black and shriveled after deposition. It is noteworthy that the pedicel
mentioned is not represented by any modification in the ovarian egg, which is
elongated and oval in form and has the anterior end smoothly rounded. This, and the fact that the pedicel
darkens and shrivels quickly after formation, would indicate that it may be
formed from secretions of the accessory glands or from material that appears
to envelop the anterior end of the ovarian egg, though this aspect has not
been studied. It may be emphasized,
also, that the pedicel is situated at the anterior end of the egg, whereas in
other pedicellate ichneumonoid eggs the pedicel and its "anchor"
are represented by definite structures on the ovarian egg and are situated at
the posterior end. As the embryo
develops, the paired caudal processes can be seen lying along the mid‑ventral
line and extending forward to the posterior margin of the head. Please CLICK on
picture to view details: The first‑instar larvae
(Fig. 41A, B) of the two species present no apparent points of
distinction. The body comprises 13 segments,
exclusive of the head, and measures 1.2 mm. in length to the base of the
caudal processes. The head is heavily
sclerotized, slightly broader than long, and bears dorsally a pair of horn‑like
structures markedly similar to those of the planidia of the
Perilampidae. There are four pairs of
minute setae dorsally and three pairs ventrally. The mandibles are simple.
Each body segment except the last bears a median transverse row of
heavy spines dorsally, and these diminish in length caudad. On the first five segments, the rows are
continuous across the dorsum, but on those following the rows are
interrupted medially. The first
segment bears two pairs of lateral setae, and the following segments bear one
pair. The venter of each of the first
eight segments bears a broad band of minute setae, and on each of the
following four segments the band is interrupted medially. The caudal segment is bifurcate, and the
two tapering, heavily sclerotized prongs are 0. 9 mm. in length, diverge at
an angle of about 80 deg., and are directed somewhat ventrad. The lobes at the base of the prongs bear
numerous robust setae dorsolaterally.
The anal opening is ventral on the last segment. There are no spiracles and no visible
internal tracheal system. Henriksen describes the supposed
first‑instar larva of A. armatus
(Fig. 42) which he states was found internally in Silo and Goera. Aside from its occurrence internally, it
differs markedly in form from the actual first‑instar larva described
by Fisher. The body is 1.4 mm. in
length, cylindrical, with the caudal end bluntly rounded and lacking the
bifurcate process. Certain
characters, however, seem to link it with the Agriotypidae, these being the
"horn‑like" structures on the head and the transverse rows of
spines on the dorsum of the body. It
seems Improbable that this larva can be of Agriotypus, but if this proves to be the case it must be
the second instar rather than the first. The second‑instar larva of A. armatus (Fig. 41D) described by Fisher differs from the
first in lacking the heavy integumentary spines, and the long bifurcate
caudal process is replaced by a pair of shorter, heavy, opposed hooks. The mandibles are conspicuously toothed. An internal tracheal system is present though
there are no spiracles, and the transverse commissures, also, are apparently
lacking. The third and last larval instar
is similar to the second, though the caudal hooks are relatively much
smaller. The head is quadrate in
form, and the mandibles are coarsely dentate. In A. armatus, there are thought to
be no spiracles, whereas nine pairs occur in A. gracilis. In view of the conditions under which the
mature larva passes the last portion of the stage, in which it is surrounded
by air rather than water, open spiracles would seem to be essential (Clausen
1940 References: Please refer to <biology.ref.htm>,
[Additional
references may be found at: MELVYL Library ] |