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).
= = = = = = = = = = = = = = =
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.