Mating of intermorphic queens in the ant, Myrmecina graminicola (Myrmicinae)

Alfred Buschinger

     Myrmecina graminicola is a European, perhaps Eurasian species with a very wide range. Due to its secluded nesting and foraging habits in the ground and in leaf litter, very little has been known on its life history. Since 1997 I have reared and bred this species because of its genetically mediated queen polymorphism (Buschinger and Schreiber 2002). Ordinary alate/ dealate queens (gynomorphs) live in monogynous colonies, whereas colonies with intermorphic (more or less workerlike) queens may be polygynous. Gynomorphs produce either only gynomorphs as female sexual offspring, or exclusively intermorphs, intermorphic queens may produce only intermorphs, or both intermorphs and gynomorphs in about equal numbers.
     The mating behavior both of gynomorphs and intermorphs has been described in Buschinger (2003). Sexually active females exhibit something like a sexual calling near the ground, only males are flying over larger distances. Poison gland secretion apparently is sometimes applied to the substratum in very small quantities, or is presented with erect gaster. It contains a sexual pheromone, as has been experimentally demonstrated with poison glands dissected out of mature females.
     Here I present a number of pictures which I was able to make only recently. The colonies had been kept in artificial annual cycles of 9-10 months over up to five natural years. Therefore it was possible to have a sexual brood during the winter 2003/ 2004, and active sexuals in January/ February this year. Two colonies were placed in arenas of 30 x 20 cm size, with two formicaries each, originally for studying nest relocation of Myrmecina (will be described later). Sexual calling and mating pictures thus are a byproduct of these experiments.

Fig 1: A sexually active gynomorph on top of the nest is "waiting" for a male. Though winged and able to fly the gynomorphs usually remain close to the mother colony. They rarely exhibit a particular posture for sexual calling.

Fig. 2: Sexual calling of two intermorphic females on top of the red foil covering the nest. They may remain there for hours, sometimes changing the site for a few centimeters. Several dozen females are sexually active in a colony, up to 60 or 70 being produced in one season. The thorax of the specimens is a bit bulky as compared to that of workers, somewhere between the shape of worker and gynomorph, but never bearing wings.

Fig 3: An intermorph in lateral view. Somewhat stilt-legged it raises the gaster. The posture is comparable to that of sexual calling Formicoxenini, except that in the latter the stinger is visibly extruded, and sometimes even a tiny droplet of poison gland secretion can be detected (eg Buschinger 1971). In Myrmecina I was unable to see the stinger during this calling behavior.

Fig 4: A male tries to mount a calling intermorph. In other ants, eg in the Formicoxenini, the male has to touch the female's antennae while trying to mount her because otherwise the female quickly escapes. Not so in Myrmecina: The female simply holds still.

Fig 5: Copulation needs about 30-60 seconds, while the male tilts backward, as in other ants.

Fig 6: Copulation is finished, the mated intermorphic queen (top right) crawls away, while a second intermorphic "princess" in (front) is still waiting. A male may inseminate 2-3 females within about one hour, whereas the females usually mate only once.

A gynomorph may found a colony independently. Intermorphs often (usually) join their mother colonies where they may become fertile, or later leave from there in a budding process.

References

Buschinger, A., 1971. Weitere Untersuchungen zum Begattungsverhalten
sozialparasitischer Ameisen (Harpagoxenus sublaevis NYL. und Doronomyrmex pacis KUTTER (Hym., Formicidae)). Zool. Anz. 187, 184-198.

Buschinger, A., 2003. Mating behavior in the ant, Myrmecina graminicola (Myrmicinae). Insect soc. 50, 295-296

Buschinger, A. and M. Schreiber, 2002: Queen polymorphism and queen-morph related facultative polygyny in the ant, Myrmecina graminicola (Hymenoptera, Formicidae). Insect soc. 49, 344-353.

Zoological Institute, Darmstadt University of Technology
Schnittspahnstr. 3
D-64287 Darmstadt
Germany
e-mail: buschinger@bio.tu-darmstadt.de