THE BIOLOGY OF MYRMOXENUS GORDIAGINI RUZSKY , A SLAVE-MAKING ANT ( HYMENOPTERA , FORMICIDAE ) BY

M’rmoxenus gordiagini was described by Ruzsky (1902) from material which he had collected in the Akmolinsk area in Soviet Russia, near the town of Koktschetaw. The ant was always found living together with a newly described host species, Leptothorax serviculus Ruzsky. The colonies inhabited narrow galleries between and underneath small stones in the rocky slopes of a hilly region, with some birch and spruce trees. Finzi (1924) described a subspecies, Myrmoxenus gordiagini menozzii, from the Yugoslavian peninsula of Istria. Only one male and one female were found within moss and soil at the foot of an oak tree, together with numerous females and workers of Leptothorax un[’asciatus (Latreille). Finzi therefore believed that his new subspecies was living with that host species. Finally, in 1925, Soudek established a new genus, M’rmetaerus, for a new species, microcellatus, that he had collected near Kotor in Dalmatia, Yugoslavia. Although he explicitly discussed the close relationship of M. microcellatus with Myrmoxenus, he described this ant as representing a new species and genus "as a provisional arrangement" (Soudek, 1925). M. microcellatus was found under a stone in a deciduous forest, in a mixed colony with Lepto-

Ps 'che [Vo. 85 thorax n'landeri (F6rster). All our material also was collected in Istria, and in the Dalmatian island Krk 3. Since the descriptions of all the three forms mentioned above are nearly identical, we assume that M'rmetaerus microcellatus and M'rmoxenus gordiagini menozzii are junior synonyms of M'rmoxenus gordiagini. We have been unable, however, to check the type material.
Nothing has been known of the biology of M'rmoxenus/M'rmetaerus except the fact that they were always found living together with a host species belonging to the genus Leptothorax Mayr, subgenus M)'rq ['ant Smith (1950), and thus apparently represent sociallyparasitic ants. W. Faber in 1972 recorded some observations on their colony foundation behavior. Recently we found out that M. gordiagini is a slave-making ant. The results of our experiments are presented in the following sections.

MATERIAL AND METHODS
W. Faber collected a total of three M.'rmoxenus colonies on 25 May 1972, on the slopes of a small valley NW of Baka, Krk. In the very same locality we found nine additional colonies between September 23 and 26, 1981. Another locality, where we gathered two colonies on 4 August 1976, and one colony on 22 September 1981, is near the ruined town Dva grada, a few kilometers east of Rovinj in lstria, and just 35 km south of the type locality of M. gordiagini menozzii. Ten of these 15 colonies contained a Myrmoxenus queen; presumably the queens of the other five colonies were either lost during collecting or were missing prior to our collecting. Myrmoxenus workers were present in varying numbers up to about 40 (exact numbers cannot be given since all colonies were kept alive for several breeding seasons, and thus produced additional workers). Two colonies contained only a queen and no workers; supposedly they were newly founded.
Male and female as well as worker pupae were present in the colonies collected on August 4, 1976, and a few adult sexuals were found in field colonies on September 22 and 23, 1981.
-Recently we found an additional population on the island Rab, south of Krk. Four colonies were collected on October 2, 1983, in an oak forest south of Suha Punta.
They contained one queen each, and in one colony we found two additional females that were delate but not inseminated.
The host species in all 15 colonies was Leptothorax lichtensteini Bondroit 1918. Up to about 200 host workers were found in the Mi'rmoxenus colonies. Nest sites were underneath small, flat stones in the soil, or in crevices between such stones. A common, and, in our opinion, quite important character of the M'rmoxenus habitats is the fact that they all were situated in rather shady places in a deciduous forest or in the underbrush. We cannot reconstruct the exact experimental device by which W. Faber studied the colony founding behavior. From his records we conclude that the colonies, which he had collected in May, produced sexuals until September. On September 9 and 22, 1972, he noted "strong flight activities," and numerous M'rmoxenus females were dealate in the nests and arenas. Several times he put five dealate Myrmoxenus females together into the feeding arenas of L. lichtensteini colonies. Others were placed into formicaries with different Leptothorax species. Our newly collected colonies from 1976 and 1981 were kept in formicaries and under artificial daily and annual temperature cycles as described by Buschinger (1973,1974,1982) and Winter (1979a). For initiating slave raids, we used arenas as depicted by Winter (1979a) and Buschinger et al. (1980). During the raids the room temperature was about 27C. Contrary to our experiences with Harpagoxenus or Epim.vrma, which need bright sunshine or at least blue sky for raiding, the Mvrmoxenus seem to prefer a clouded sky.
Thus, the first raid which we observed in our labroatory took place on a cloudy day; for the second one, on a sunny day, we closed the window shades.

COLONY FOUNDING BY MYRMOXENUS GORDIAGIN1
As indicated above, we rely on the quite brief notes of W. Faber, who observed colony founding by M. gordiagini females in 1972. According to these notes, the young Myrmoxenus queen enters a host species colony (L. lichtensteini), apparently soon after mating and dealation, in late summer. Most Myrmoxenus females were attacked and often killed by workers of the host species. In a few experiments, however, a parasitic queen survived the attacks and at last was accepted by the host species workers. She then assaulted the host species queen in a very characteristic manner (Fig. 1). She grasped the Leptothorax queen's "throat" with her mandibles, and Iron. 8 throttled her repeatedly, and often for several hours, as was described for Epim)'rma ravouxi females (Gtisswald 1930). Other M'rmoxenus queens were seen to throttle the Leptothorax queens by seizing their necks from the back. Like Epimyrma stumperi females (Kutter 1951) the Myrmoxenus queeos also scent themselves by first rubbing their legs over the surface of the victims, and then over their own backs. Sometimes the Myrmoxenus queens throttled some host species workers, too, or stung them to death. Furthermore, they attacked the alate Leptothorax females which were present in the nests, and killed some of them. In one L. lichtensteini colony, where five Myrmoxenus females had been put on September 12, the lichtensteini queen was dead on September 17, and one surviving M'rmoxenus female was observed to bite the large queen larvae of the host species.
Experiments with L. parvulus (Schenck 1852) as host species did not succeed; the M'rmoxenus queens were all killed.

SLAVE RAIDS OF MYRMOXENUS GORDIAGIN!
We observed two slave raids of one M,rmoxenus colony, on June 24 and July 7, 1982. The colony was collected in September, 1981. After an artificial hibernation from 12 December 1981, in a constant 6C until 22 April 1982, the colony began to bring up its larvae. The first prepupae appeared on 4 June, six weeks after the end of hibernation, the first worker and sexual pupae were recorded on 11 June. Sexuals hatched towards mid-July, after the raids, and sexual activity was observed in the beginning of September. A second colony, which was kept under identical conditions, exhibited some scouting activity between June 4 and 25, but did not conduct a raid.
The first colony was put into an arena on 4 June. Simultaneously a colony of the host species, L. lichtensteini, was placed into another part of the arena, which was subdivided by a plastic wall.
No M'rmoxenus workers were seen outside the nest until 22 June.
On June 23 and 24, between one and three M'rmoxenus workers appeared in the arena. Scouting occurred between 1000 and 1500 on June 23. On June 24, a hole in the separating wall of the arena was opened, and a Mvrmoxenus scout found the way through to the host species territory at 1740. At 1754 this scout ran across the lichtensteini nest. It returned to the Mvrmoxenus nest, entered there at 1804, and suddenly a mass of ants was whirling around inside the nest entrance.
At 1808, a file of about 20 M'rmoxenus came out of the nest (Fig. 2) and walked across the arena towards the hole. Sometimes the procession stopped, milling around, apparently until the leading scout had found its way again.
At 1905 the group had reached the entrance of the target nest, and entered it one after the other. Almost no fighting could be observed. After 6 minutes, the lichtensteini queen and most of the workers had left their nest, carrying a few small larvae and eggs.
Only two Leptothorax were stung. Some M.vrmoxenus workers Psyche [Vo. 85 Fig. 2. A raiding party of Ml'rmoxenus gordiagini has just arrived at the nest of the host species (photograph: Buschinger). returned to their own nest, and at 2030 another file of 5 M.vrmoxenus arrived at the Leptothorax nest. By the next morning, the Myrrnoxenus colony had moved into the former Leptothorax nest.
The arena was then subdivided again, and a new Leptothorax nest was placed in the position of the former M.vrmoxenus nest.
The second raid, in the same arena, was observed two weeks later, on 10 July. Scouting began at 0830 and a successful scout returned to the M),rmoxenus nest at 0912. However, in this case, a file did not form before 0933. At 1009 a total of 14 M.vrmoxenus arrived at the target nest, entered it at 1012, and a few minutes later they had overwhelmed the colony and were in possession of its brood. Eight Leptothorax were immediately stung to death. Contrary to the first raid, this time the Myrmoxenus soon began to carry pupae and large larvae back into their own nest. One returning Myrmoxenus, at 1150, led a further file of 15 conspecifics to the raided nest. At 1320 the Leptothorax nest was empty except for a few eggs and one Leptothorax male. A total of 26 dead Leptothorax workers were counted in the arena, indicating that during this raid more fighting had occurred than during the first one.

DISCUSSION
Our results, despite the low number of raids observed, reveal that M)'rmoxenus gordiagini is a slave-making ant. The organization of the raids is essentially the same as in Epimyrma ravouxi (Andr6) (Winter 1979b, Buschinger et al. 1980, and in the North American Leptothorax duloticus (Wesson 1940), with group recruitment and sting fighting.
The colony foundation behavior of M.vrmoxenus also corresponds to that observed in several species of the genus Epimyrma (Kutter 1951, Gtisswald, 1930, Buschinger andWinter, in press), where the queens throttle the host species queens. The only major difference between Mvrmoxenus and Epimyrma, therefore, pertains to antennal segmentation. Myrmoxenus females and workers have 12-segmented antennae (males 13), like their host species group, whereas Epimyrma has l-segmented antennae (males 12). We have not yet decided whether this difference can really justify the maintenance of the two genera; however, we are convinced that the very particular raiding and colony foundation behaviors have a monophyletic origin.
We are not entirely certain that M.vrmoxenus gordiagini is the correct name of our ants. That they are identical with Finzi's M. g. menozzii (1924) seems assured, since they were collected in the same area. We are also sure about the identity of this M. g. menozzii with Soudek's (1925) Myrmetaerus microcellatus. However, if a later revision reveals that M. gordiagini R uzsky and M. g. menozzii Finzi were two different species, then our material should be named M. menozzii.
The different host species recorded for the three "forms" represent a minor problem. Slave-making ants often have more than one host species. Thus, Epim)'rma ravouxi (Andre) enslaves Leptothorax un['asciatus (Latr.), L. nigriceps Mayr, and L. q['finis Mayr, sometimes having two slave species together within one colony (G6ss- wald 1930). It is also quite conceivable that both Finzi and Soudek found their ants, as we did, with L. lichtensteini as host species; L. lichtensteini has a superficial resemblance to L. unfasciatus, and it is quite often confused with L. nylanderi. SUMMARY M)'rmoxenus gordiagini Ruzsky from Dalmatia, Yugoslavia, conducts slave raids with group recruitment and sting fighting.