Full resolution (JPEG) - On this page / på denna sida - I. Description of the developed (imaginal) stages of Chordeuma obesum n. g., n. sp.
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The anterior part of the abdomen is broad and swollen, intimately joined to
the hindmost thoracic segment. The whole abdomen represents three segments, but
these are not distinctly marked out. By far the greater part is the genital segment
(g); laterally this sends out a large, rounded, terminally somewhat deepened process
(l), ventrally it carries the two genital openings (g0); the latter are close together,
semilunar, almost in contact with their convex sides; in front of them is often, but
by no means always found an unpaired rounded prominence or hunch[1]. The
posterior part of the genital segment is somewhat tapering; from a deepening in this
part the rest of the abdomen (representing two segments) protrudes as a short and
narrow appendix (ap), dorsally at its base sending out a blunt process and terminating
with two bifurcated claws. There is no anus, and no trace of an intestine is
contained in the abdomen.
Young females (Pl. I, Figs. 5, 6, 7) differ in general shape and several details a
good deal from the ripe. The smallest females found after metamorphosis are
0,832—0,912 mm in length; probably their form is essentially the same as that
possessed immediately after emerging from the larval cuticle; but while I have found a
great many young males together with the cast larval skin, I never succeeded in
finding with certainty the same case for the young females. The outer shape of the
smallest females is very nearly that of the somewhat larger, ca. 1 mm in length,
represented on Pl. I Figs, 5—7.
The body is less clumsy than in the mature female, more cylindrical, without
constriction between the second and third thoracic segments; the genital segment (g)
is less prominent, its lateral processes (l) conical and directed backwards; all
appendages are proportionally larger, the thoracic feet on second, third and often also the
fourth pair provided with very distinct rudiments of an inner branch (i). The
modifications leading to the final shape and maturity are performed simply during
growth, without any moultings. I have particularly directed my attention to the question
of moulting, but I never saw anything indicating the formation of a new cuticle
below the older one, and I am quite sure that after the casting of the larval envelope
no further moulting takes place[2].
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