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File: <trigo1.ima.htm> [For educational purposes only] Terminology Glossary <Principal Natural
Enemy Groups > <Citations> |
Immature Stages of Trigonalidae
Immature stages of Trigonalidae were discussed in detail by Clausen
(1940), as follows: The microtype egg of P.
thwaitesiii (Fig. 26A)
measures 0.12 by 0.07 mm., is ovoid in form, flat ventrally, and arched
dorsally, and bears a series of 5-7 longitudinal ridges on the dorsum. The chorion is exceedingly hard and
translucent. Other species observed
have eggs of similar form, with slight variations in size and in the number
and prominence of the longitudinal ridges.
Those of N. jezoensis are said to be convex
on both sides. The microtype first‑instar
larvae have been described only for P.
maga (Fig. 26B) and Orthogonalis debilis (Clausen, 1931), and
these are very similar in form. They
are 0.12 mm. in length, with 12 body segments, broadest in the thoracic
region and tapering gradually caudad.
The head is broad, largely retracted into the thorax and the mandibles
are slender and extruded. The first
thoracic segment has a transverse ventral row of five exceedingly heavy
hooks, directed caudad, and is heavily sclerotized palmate plate dorsally on
the median line. The 2nd & 3rd
segments have the row of heavy spines both dorsally and ventrally. Each abdominal segment has a transverse
row of minute setae both ventrally and dorsa11y, those on the last two or
three segments forming a complete ring. Please
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picture to view details:
The intermediate‑larval instars have been described for P. thwaitesii only, and these were secured by dissection
of parasitized Henicospilus larvae taken from their cocoons. The 2nd instar (Fig. 26C) is markedly
different from the 1st, having a large hemispherical head, with large but
lightly indurate mandibles, and 12 body segments which bear no hooks or
setae. The 3rd instar (Fig. 26D) is
of the mandibulate type similar to the 1st instar of many other
Ichneumonoidea. It has a single pair
of spiracles at the anterior margin of the 2nd thoracic segment. The 4th instar larva (Fig. 26E) is more
slender, with the head of normal form, and the caudal segments are somewhat
attenuated. There are eight pairs of
spiracles, situated on the 2nd & 3rd thoracic and the 1st 6 abdominal
segments, of which the first pair is much the largest. The 5th instar (Fig. 26F) is very robust
in form and bears no integumentary spines or setae. The spiracles are as in the preceding instar. The mandibles are tridentating as compared
with the simple form of those of the preceding instars. References: Please refer to <biology.ref.htm> [Additional references may be found at: MELVYL Library] |
