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HYMENOPTERA,
Methocidae (Vespoidea) -- <Images> & <Juveniles> Description & Statistics
Research on the cosmopolitan genus Methoca, indicates that this genus is parasitic only on
Cicindelidae. Philippine species, M. striatella
Williams (Williams 1919) represents the general behavior of the family. Females of this and other species are
ant-like in appearance, and lack wings.
On the other hand, males are much larger, more robust and have bully
developed wings. Female Methoca search out the vertical burrow
of the host in the soil, within which the tiger beetle host larva occurs, and
awaits its ascent to the entrance.
The beetle larva is much larger than the parasitoid and is equipped
with formidable jaws. The normal
procedure in attack seems to be for the parasitoid to permit herself to be
seized by the larva. Then the sting
is quickly inserted in the host's throat or thorax. However, sometimes she descends to the larva in the burrow,
brings her ovipositor forward beneath the body and inserts it by a quick
thrust, or she may enter the burrow backward and sting in that position. The host is permanently parasitized. A short time may then be spent by the
parasitoid in pinching the ventral portion of the abdomen with her mandibles,
after which the egg is deposited longitudinally on the ventral surface of the
3rd or 4th abdominal segment. After
this the burrow is filled with soil. The egg is 1.0 mm. long, cylindrical, slightly curved, and
narrower at the posterior. Incubation
is finished in ca. 2 days. After
hatching, the young larva feeds first through a minute puncture in the
integument, and later the head and some of the throat are buried in the
wound. Feeding takes only 5-6 days,
and due to the host's great size, the body contents may not be completely
consumed. The cocoon consists of a
compact inner layer and a light outer envelope, tapers posteriorly and at the
anterior end the outer covering has a wide flaring mouth. The inner cocoon has a construction at the
base of the collar, which is united with the flaring mouth. The host remains may frequently be found
within this cub, and 10-20 days are spent in the cocoon stage, the cycle
being completed in less than a month (Clausen 1940/62). Brothers & Finnamore (1993) considered this group as the
subfamily Methocinae (misspelled "Methochinae") in the
Tiphiidae. They are widespread, but
are absent from the Australian region.
There are only a few species in 2 genera. Sexual dimorphism is extreme:
males are usually black, and females are mostly black and/or red. The larvae are ectoparasitoids on the
larvae of soil-dwelling Cicindelinae (Coleoptera). Four species in one genus occur in North America (one species
in Canada). European M. ichneumonoides Latr. was studied by
Adlers (1905), Champion (1914, 1915), Pagden (1926) and Main (1931). This species behavior is essentially the
same as that of M. striatella, although during
oviposition the female permits the host to seize her head or thorax between
the mandibles, after which the sting is inserted in its throat. The egg is placed obliquely behind and on
the inner side of the base of the hind leg.
M. styga Say lays its eggs in the same position, but M. punctata
Williams places it longitudinally on the underside of the 3rd abdominal
segment, with the anterior end directed forward. Two species of Methoca studied
by Iwata (1936) show certain differences in behavior. In M.
japonica Yasum., there is the
typical preliminary stinging in the burrow.
However, the paralyzing effect is not so rapid, and the victim usually
rushes out of the burrow. There it is
sung again, at times more than once, and is dragged back into the burrow,
after which the egg is laid in a diagonal position behind one of the hind
coxae. Paralysis is complete but not
permanent, and the larva revives to resume its normal activities. There is no thelytoky known in this family as of 1940 (Clausen
1940/62). = = = = = = = = = = = = = = = References:
Please refer to <biology.ref.htm>, [Additional references may be
found at: MELVYL Library] Agnoli, Gian
Luca. 2005. The genus Methocha
in Europe: a discussion on taxonomy,
distribution and likely origin of its known species and subspecies
(Hymenoptera Tiphiidae Methochinae).
Bull. Insectology 58(1):
35-47. Pagden, H. T.
1949. Descriptions and records
of Austro-Malaysian Methocidae and Mutillidae (Hymenoptera). Transactions of
the Royal Entomological Society of London, Vol. 100. Part 8: 100-8. London,
pp.191-231, 14 text-figures. |