Acropyga and Azteca Ants (Hymenoptera: Formicidae) with Scale Insects (Sternorrhyncha: Coccoidea): 20 Million Years of Intimate Symbiosis

Home , Acropyga, Aphomomyrmex, Azteca (ant), Cladomyrma, Trophobiosis

PUBLISHED BY THE AMERICAN MUSEUM OF NATURAL HISTORY CENTRAL PARK WEST AT 79TH STREET, NEW YORK, NY 10024 Number 3335, 18 pp., 10 ®gures June 22, 2001

CHRISTINE JOHNSON,1 DONAT AGOSTI,2 JACQUES H. DELABIE,2 KLAUS DUMPERT,3 D. J. WILLIAMS,4 MICHAEL VON TSCHIRNHAUS,5 AND ULRICH MASCHWITZ3

ABSTRACT Species of the genus Acropyga are rarely encountered subterranean ants that rely on mealybugs or aphids to provide their nutritional needs. Female Acropyga (Formicinae) alates of pantropical and Mediterranean species carry mealybugs with their mandibles while swarming and probably inoculate their new nests with these mealybugs. The natural history of Acropyga and other mealybug-tending ant species, a summary of the various reports of Acropyga females toting mealybugs, and a new record from French Guiana are presented here. Also provided are a ®rst report and description of Acropyga alates with mealybugs in Dominican amber dated to the Miocene, a discovery indicating that this intimate association and relatively uncommon behavior has existed for at least 15±20 million years. The mealybugs found with the Acropyga females in amber are related to the hypogaeic genera Eumyrmococcus Silvestri and Neochav- esia Williams & Granara de Willink (Pseudococcidae, Rhizoecinae) and represent three new species of a new genus. The genus Electromyrmococcus and the species Electromyrmococcus abductus Williams, Electromyrmococcus inclusus Williams and Agosti, and Electromyrmo- coccus reginae Williams are described. A piece of Dominican amber containing workers of Azteca alpha Wilson (Dolichoderinae) and 23 scale insects is also presented and the signi®- cance of these specimens in Dominican amber is discussed.

INTRODUCTION a variety of arthropods (reviewed in HoÈll- Of the numerous symbiotic relationships dobler and Wilson, 1990). The trophobiotic known from animals, few are as impressively associations, which involve the trophobiont intimate as those that occur between ants and providing nutrient-rich excretions or secre-

1 Scienti®c Assistant, Division of Invertebrate Zoology (Entomology), American Museum of Natural History. 2 Research Associate, Division of Invertebrate Zoology (Entomology), American Museum of Natural History. 3 Professor, Fachbereich Biologie und Informatik der Johann Wolfgang Goethe UniversitaÈt, Frankfurt/Main, Ger- many. 4 Department of Entomology, Natural History Museum, London. 5 Professor, FakultaÈt fuer Biologie, UniversitaÈt Bielefeld, Bielefeld, Germany.

TABLE 1 Species of Dolichoderus Herder Ants and of Allomyrmococcini Mealybugs Herded, and Region

tions in exchange for protection from natural stages of symbiotic evolution suggest that enemies by the ants (e.g., Pierce and Easteal, these associations have evolved indepen- 1986; DeVries, 1991), appear to be particu- dently numerous times. In the most advanced larly successful, with numerous Lepidoptera stages of trophobiosis, the relationship be- (e.g., lycaenids, riodinids, and tortricids tween participants is obligatory. Among [Maschwitz et al., 1986, 1987; Fiedler and those obligatory relationships that involve Maschwitz, 1989; HoÈlldobler and Wilson, homopterans, ants establish new nests or col- 1990]), Heteroptera (Maschwitz and Klinger, onies with their trophobiont, transferring one 1974, Maschwitz et al., 1987), as well as or more directly from the parent colony. At Sternorrhyncha and Auchenorrhyncha (Mas- least 12 Dolichoderus (Dolichoderinae) ant chwitz, 1990) serving as the trophobiont. species from Southeast Asia were discovered Trophobiotic interactions may involve mere- recently to herd more than 24 species of ly the harvesting of honeydew excretions mealybugs in 10 genera (see table 1). These from some Coccoidea, or ants may actually Dolichoderus herdsmen establish new colo- stimulate the trophobiont to exude honeydew nies by ®ssion and the workers bring with by stroking them. them a self-contained colony of mealybugs The many thousands of species of scales (Maschwitz and HaÈnel, 1985; Dill and Mas- (Coccoidea), green¯ies (Aphidoidea), white- chwitz, 1998, Maschwitz and Dill, 1998). ¯ies (Aleyrodoidea), plant lice (Psylloidea), In other genera, the trophobiont is brought and various membracids or fulgorids that live to the new nest site by young gynes. Gynes in trophobiosis with ants exhibiting different of the myrmecophytic ant, Aphomomyrmex 2001 JOHNSON ET AL.: ACROPYGA AND AZTECA ANTS 3

Fig. 1. World distribution of Acropyga subgenera (from Emery, 1925; Menozzi, 1936; Weber, 1944; Prins, 1982; Terayama, 1985; Williams, 1998). afer (Formicinae), passively transfer the tro- tivated plants as well as some of the native phobiont to a new host plant via phoresis plants on which the pseudococcids feed (Gaume et al., 2000). Young gynes of the (BuÈnzli, 1935). There are two kinds of gal- Southeast Asian ant Tetraponera sp. near at- leries, or chambers, in Acropyga ant nests tenuata F. Smith (Pseudomyrmecinae) and of (BuÈnzli, 1935; Weber, 1944; Delabie et al., Acropyga (Formicinae), on the other hand, 1991). The ``blind'' alley, where the mealy- carry a trophobiont in their mandibles while bugs feed and are tended or ``milked'' by the swarming and bring it to the new nest site, a ants, is a chamber that extends along the behavior that appears cognate to the transfer roots of the plants; the other chamber is used of symbiotic fungus by young gynes estab- for rearing both ant and mealybug broods. lishing colonies in the fungus-growing Attini The mealybugs rely on the workers to carry of the New World (Weber, 1972). The gynes them through the galleries, and the ants ap- of Tetraponera sp. near attenuata F. Smith, pear to regulate honeydew production by which lives within the large hollow inter- adding or removing the mealybugs from the nodes of certain giant bamboo species (Klein roots (Flanders, 1957). This network of un- et al., 1994), transport their trophobionts to derground tunnels may also be used to trans- empty bamboo internodes that had been ex- port the mealybugs from nest site to nest site. cavated previously by stem-feeding pyralid Acropyga workers rarely, if ever, emerge caterpillars. Tetraponera gynes have been from underground and, not surprisingly, have observed holding a mealybug for as long as minute eyes and little cuticular sclerotization 32 hours (Klein et al., 1992)! and coloration. Although rare in the species-rich, arbori- Currently, four subgenera of Acropyga are colous pseudomyrmecine genus Tetrapo- recognized (Acropyga sensu stricto, Atopo- nera, the carrying of mealybugs by swarm- don Forel, Malacomyrma Emery, and Rhi- ing gynes is widespread among the ground- zomyrma Forel [Emery, 1925]) and each has dwelling, formicine genus Acropyga Roger. a relatively well-de®ned geographic distri- Colonies of Acropyga species that tend pseu- bution (see ®g. 1 for world distribution). Ac- dococcids in South and Central America are ropyga (Rhizomyrma) paramaribensis Borg- found in mature tropical forests (Weber, meier and A. (R.) rutgersi BuÈnzli are oblig- 1944); in cacao, coffee, and banana planta- atory coccoidophiles that tend Pseudococci- tions (BuÈnzli, 1935; Weber, 1944); and in dae from a total of four genera. Acropyga grassy pastures (Weber, 1944; Eberhard, paramaribensis tends ®ve species of pseu- 1978). The colonies tend to be large and of- dococcids, one of which has also been found ten surround the roots of many of these cul- in nests of A. rutgersi, in the genera Rhizoe- 4 AMERICAN MUSEUM NOVITATES NO. 3335 cus, Geococcus, and Pseudorhizoecus. of the specimens survived in the dishes more Whereas four of these pseudococcid species than three hours. The swarm was approxi- have been found living independently, Pseu- mately 2.5 m high, making it dif®cult to de- dorhizoecus proximus Green and three other termine conclusively whether all the gynes species have only been found living with Ac- were carrying mealybugs. Nonetheless, each ropyga, evidence supporting their obligatory gyne collected was holding a mealybug, sug- relationship. Acropyga (R.) decedens in Bra- gesting that all had taken ¯ight with mealy- zil was reported tending Geococcus and Rhi- bugs. That each gyne appeared to be carrying zoecus mealybugs (Delabie et al., 1991). Ta- a mealybug is similar to observations made by ble 2 lists all the mealybugs species known Eberhard (1978) of swarming Acropyga in Co- to associate with Neotropical Acropyga. lombia. No males were observed toting mealy- Although three of the four subgenera are bugs and have never been reported doing so. known to have alate gynes that tote coccoids Table 3 lists all the records of alate female Ac- during nuptial ¯ights, observations are rela- ropyga carrying pseudococcids; a representa- tively rare and little is known about the age of tive alate female Acropyga from South Africa this behavior. Here we report a new record of carrying a mealybug is illustrated in ®gure 3. Acropyga gynes carrying mealybugs from Some of the alate and dealate gynes car- French Guiana and the discovery of several rying coccoids were preserved in ethanol. pieces of Dominican amber from the Miocene Several were critical point dried and exam- that contain Acropyga gynes with mealybugs, ined with a scanning electron microscope. an indication that ants have had some type of The habitus of the female mealybug is typi- symbiotic association with mealybugs for at cally oval, and mandibles of the Acropyga least 15±20 m.y. The mealybugs in each of the gyne are distinctly scapulate, perhaps related three amber pieces represent three new species to fossorial life but probably also for gentle of a new genus and are described (see appen- transport of the tender coccids (®g. 4a, b). dix 1). A piece of Dominican amber containing The species of Acropyga was not determined workers of Azteca alpha Wilson and 23 scale since the genus is in need of revision, despite insects is also presented and the signi®cance the treatment by Weber (1944). lt is quite of ®nding scale insects together with ants in possible that this ant is one of the two species amber is discussed. of Acropyga reported by BuÈnzli (1935) from nearby Surinam. NEW RECORD OF EXTANT ACROPYGA Whether the mealybugs carried by the gy- TOTING MEALYBUGS nes had mated was not determined. Report- edly, many coccoids taken on nuptial ¯ights Observations and samples were taken by C. are mated females; however, others may be Johnson in central French Guiana (3Њ38ЈN, unmated females or even immature males 53Њ13ЈW, approx. 300 m elevation) on Decem- that resemble females (BuÈnzli, 1935). In ei- ber 26, 1996, near the town of SauÈl, approxi- ther case, this is unlikely to be problematic mately 6 weeks into the rainy season. A small (1) since females of many mealybug species swarm of male and female Acropyga was are parthenogenetic and thus could produce found during the early afternoon of a sunny offspring in the new nest, and (2) if Acro- day marked by only brief periods of light pyga is largely pleometrotic, as is Acropyga morning rain in a clearing of several acres that paramaribensis (BuÈnzli, 1935), and some co- had several cabins and small plantations of foundresses transport female coccoids in ad- fruits and vegetables. The surrounding area dition to others transporting male coccoids to was intact, mature lowland Amazonian rain- the new nest site. forest, which received an average annual rain- fall of 240 cm/yr. Specimens from the swarm AMBER FOSSILS OF ACROPYGA were collected and placed into small petri dishes (®g. 2). Several gynes were in copula and, Three pieces of Dominican amber, each after decoupling, promptly removed their containing an Acropyga gyne with a pseu- wings without releasing the mealybug. None dococcid, were recovered from approximate- 2001 JOHNSON ET AL.: ACROPYGA AND AZTECA ANTS 5

TABLE 2 Mealybugs Associated with Neotropical Acropyga (corrections made by D. J. Williams)

ly 30,000 small pieces of Dominican amber mixed together. Hence, exact provenance of screened by D. Grimaldi. Two pieces, which these pieces cannot be stated with certainty. contain complete gynes, are in the amber fos- However, recent stratigraphic and other evi- sil collection of the Division of Invertebrate dence presented by Iturralde and MacPhee Zoology, AMNH. The third piece, in which (1996) and Grimaldi (1995) indicate that all only a portion of the gyne is preserved, is in pieces are approximately contemporaneous the private collection of Roy Larimer. Vir- and were formed in the mid- to lower-middle tually all Dominican amber pieces that are Miocene (15±20 Ma). The fourth piece of sold through dealers from Santiago and San- Dominican amber was provided by M. v. to Domingo come from various mines but are Tschirnhaus (Frankfurt collection) and con- 6 AMERICAN MUSEUM NOVITATES NO. 3335

Clypeus bearing long hairs (especially on anterior margin); antennae 9-segmented. Prono- tum very short; mesonotum much higher than pronotum, nearly ¯at on top, as long as wide, with rounded corners. Gaster more than 1 mm in length, tapered posteriorad. Wings translu- cent, with single cubital cell; veins brownish- yellow. Male: Length approximately 1.5 mm. Color distinctly darker than that of females, especially head and alitrunk. Head nearly as long as broad; eyes more than half head length, reaching from anterior clypeal margin to occiput. Mandibles long and narrow; antennae 10-segmented; scapes projecting beyond occipital margin. Ocelli protruding considerably. Al- itrunk only slightly broader than head width; Fig. 2. Acropyga from SauÈl, French Guiana. mesonotum slightly convex, much higher than An alate gyne carrying a mealybug while in cop- propodeum; propodeum rounded on top with ula. short part descending perpendicularly. Petiole base in pro®le broad, tapering to transverse ridge. Wings with single closed cubital cell. tains two Acropyga gynes with mealybugs Harvard collection: Specimen AMNH and a male ant. This piece is approximately DR-10-228 is a dealate gyne (®g. 5c); her contemporaneous with the other Dominican cuticle and that of the scale insect are slightly amber pieces. Roy Larimer provided the ®fth distorted by compression. Specimen AMNH amber piece, which contains workers of Az- DR-14-403 (®g. 5d) has an inner droplet of teca alpha Wilson and mealybugs. amber at the core, bearing a complete alate One amber piece from the Dominican Re- gyne that has been perfectly preserved and a public (Frankfurt collection) contains a single mealybug (®g. 6 [detail]) fortuitously dis- alate Acropyga gyne holding a mealybug be- lodged from her mandibles. See appendix 1 tween her mandibles and one Acropyga male for descriptions of mealybugs. (®gs. 5a [detail] and 5b). The genus of the The queens from specimens AMNH DR- specimen was determined using the original 10-228 and AMNH DR-14-403 resemble description of Roger (1862). Of the four sub- each other strongly with respect to head genera of Acropyga, only Rhizomyrma is re- shape (®g. 5c, d). The head shape, however, corded from the New World. Forel (1893) es- is distinctly different from the Frankfurt col- tablished Rhizomyrma as a subgenus of Acro- lection specimen (®g. 5a, b). Whereas the oc- pyga, the characteristics of which are clavate cipital corners of the Frankfurt specimen are antennae with 7±11 segments, 2-segmented rounded and the occiput is nearly straight, maxillary and 3-segmented labial palpi, long, the Harvard queens have distinctly pro- narrow mandibles with 3±4 teeth on an ex- nounced occipital corners and an impressed tremely oblique border, extremely small eyes, occiput. Thus, the Frankfurt and Harvard no ocelli, and triangular and distinct frontal queens represent different species. area. The single female that Forel examined lacked wings and was described merely as workerlike. The male caste was not described. AMBER FOSSILS OF AZTECA Dominican amber piece AMNH DR-14- SPECIMEN DESCRIPTIONS 955 (2.4 ϫ 2.8 ϫ 1.1 cm) contains 9 workers Frankfurt collection (®g. 5a, b): Female: of Azteca alpha Wilson and 20 female/ Length nearly 3 mm. Color light, no darker nymphal and 3 male pseudococcids, plus de- than light brownish-yellow. Eyes normal size, bris and a female cecidomyiid midge (®g. 7). situated very close to base of mandibles. Ocelli The mealybugs are not the same taxon as close together, situated in small indentation. those discussed above; in fact, their mor- 2001 JOHNSON ET AL.: ACROPYGA AND AZTECA ANTS 7 TABLE 3 Gynes Carrying Coccids (corrections made by D. J. Williams) Acropyga Observations of 8 AMERICAN MUSEUM NOVITATES NO. 3335

the center of the dorsal surface of each mealybug, including various instars, suggests that the mealybugs in this amber piece have exuded wax, possibly from between abdominal segments 3 and 4. Thus, it has been hy- pothesized that these mealybugs were not as intimately symbiotic with Azteca as are the mealybugs with Acropyga (J. Koteja, personal commun.). It is, however, almost certain that these coccoids were tended by the ants, even though none of the workers is actually carrying a mealybug. Azteca species, like most dolichoderines, are renowned for tending homopteran insects. And while Azteca alpha is probably the most common insect species in Dominican amber, comprising at least 30%, and perhaps as much as 50%, of all ant inclusions, coccoids, particularly nymphs, are extremely rare. The chance of ®nding a clus- Fig. 3. Alate female of a South African Ac- ter of coccoids in a piece of Dominican am- ropyga carrying a Eumyrmococcus mealybug (re- ber is in®nitesimally small, as is the chance drawn from Prins [1982] by Williams [1993]). of ®nding a fortuitous cluster of coccoids and Azteca alpha ants. The presence of males and phology is much more generalized than the females coccoids at several developmental morphology of mealybugs that are obligate stages indicates that the amber captured them trophobionts. For example, the body shape is virtually in situ. Although the transport of oval, not elongate-pyriform, and the antennae mealybugs by Acropyga gynes implies a are relatively short. Furthermore, the small to symbiotic relationship, this amber piece with fairly large cloud of milky substance around Azteca ants and mealybugs is probably the

Fig. 4. Scanning electron micrographs (40±50ϫ)ofanAcropyga gyne from SauÈl, French Guiana, carrying a mealybug (collected by C. Johnson). a. Frontal view. b. Oblique lateral view. 2001 JOHNSON ET AL.: ACROPYGA AND AZTECA ANTS 9

Fig. 5. a. Acropyga sp. 1, gyne with mealybug between mandibles in amber from the Dominican Republic (Frankfurt collection piece, detail). b. Acropyga sp. 1, alate gyne and male in Dominican amber (Frankfurt collection piece). c. Acropyga sp. 2, dealate gyne and mealybug in Miocene amber from the Dominican Republic (Harvard collection piece, AMNH DR-10-228). d. Acropyga sp. 2, alate gyne and mealybug in Miocene amber from the Dominican Republic (Harvard collection piece, AMNH DR-14-403). 10 AMERICAN MUSEUM NOVITATES NO. 3335

comyrma from new collections of New Jer- sey amber, as well as several other genera of primitive ants based on males, and even a new genus of a very primitive ponerine. Gri- maldi et al. (1997) reviewed and evaluated all of the Cretaceous records of ants, and concluded that the specimens in amber are the only de®nitive Cretaceous Formicidae; the specimens compressed in rock lacked critical features and were deemed ambigu- ous. Thus far, all ants in Cretaceous amber are among the most primitive morphologi- cally and it is likely the origin of the true ants dates approximately 100±120 Ma. The fossil record for ants is exceedingly poor in the lowest Tertiary (Paleocene). Only a few taxa are described from the amber of Sakhalin Island, Far East Russia (Dlussky, Fig. 6. Mealybug (detail) in amber (Harvard 1988), apparently Paleocene in age, whereas collection piece, AMNH DR-14-403). several taxa are described from Eocene Arkan- sas amber (Wilson, 1987) and more than 50 genera and hundreds of species are reported earliest documentation of actual homopteran- from early Eocene Baltic amber (Wheeler, tending behavior. 1915). The lower Tertiary ants indicate a glob- al fauna that was entirely transformed from the DISCUSSION Cretaceous fauna, mostly with the emergence of modern subfamilies in the Paleocene (al- Considering the disparate geological records though the Ponerinae actually appear in the of ants and pertinent groups of homopterans, Cretaceous) and many modern genera in the particularly Sternorrhyncha, the discovery of early Oligocene (Lutz, 1986). current symbiotic relationships in Miocene amber has profound implications for understand- ing ant and homopteran coevolution. FOSSIL RECORD OF THE STERNORRHYNCHA The evolutionary history of Sternorrhyn- FOSSIL RECORD OF THE ANTS cha greatly exceeds the evolutionary history Knowledge of Cretaceous ants began of ants. Heie (1987) reviewed the fossil re- merely 30 years ago, with the discovery of cord of aphids (superfamily Aphidoidea), two workers (Sphecomyrma freyi Wilson and and determined the oldest record thus far to Brown) in a piece of Turonian (90±94 Ma) be Triassoaphis cubitus Evans from the Tri- amber from central New Jersey (Wilson et assic of Australia. From the Cretaceous am- al., 1967a, 1967b). In the last 15 years, how- ber of Canada, Richards (1966) reported six ever, many new species and genera of Cre- genera in three families; from Siberian am- taceous ants have been described, primarily ber, Konova (1976, 1977) reported eight from mid to upper Cretaceous rocks and am- families, two of them extant. Aphid nymphs ber of Russia and Kazakhstan (Dlussky, are common in both of these ambers and are, 1975, 1983, 1987); from Aptian limestone in fact, the most abundant inclusions in Ca- (ca. 110 Ma) of Brazil (BrandaÄo et al., 1990); nadian amber. This strongly contrasts with and from upper Cretaceous amber of Canada the slightly older New Jersey amber, in (Wilson, 1985a and unpub. data). Wilson which aphids are extremely rare (only two (1987) revised the taxonomy of Dlussky's specimens out of 1000 insects have been Cretaceous ants, synonymizing several gen- found thus far) and coccoids are the most era. Recently, Grimaldi et al. (1997) reported abundant kind of inclusion (20% of all inclu- another worker and a possible male of Sphe- sions) (Grimaldi, 1997). Coccoids are very 2001 JOHNSON ET AL.: ACROPYGA AND AZTECA ANTS 11

Fig. 7. Azteca alpha Wilson workers with mealybugs in Dominican amber (Larimer piece, AMNH DR-14±955). A ϭ Azteca alpha Wilson; M ϭ mealybug; C ϭ Cecidomyiidae. rare in Canadian amber, and it is unknown ones [Electrococcus canadiensis Beardsley whether the difference between Canadian (1969)] are in Canadian amber, and undes- and New Jersey amber is due to ecological cribed forms are in Siberian and New Jersey replacement of one sternorrhynchan group ambers. The specimens we found in Miocene for the other, or to taxonomic circumstance. amber belong to an extinct coccoid genus Coccoids have a sparser fossil record, one that had already radiated into three different that is restricted primarily to the Cretaceous, species (see appendix 1). Koteja (1989) has and virtually all of the specimens are in am- listed the Mesozoic scale insect fossils. In the ber, a probable result of their frail, minute Oligocene, seven families were preserved in bodies. The oldest coccoids are in lower Cre- Baltic amber, all of which are still in exis- taceous amber of Lebanon, whereas younger tence (Koteja, 1985, 1987). 12 AMERICAN MUSEUM NOVITATES NO. 3335

AGE AND TRENDS OF ANT±HOMOPTERAN probably originated in the New World where SYMBIOSES the earliest ®ndings are preserved in Miocene amber. The restricted distribution of the Tetra- The Dominican amber specimens of Ac- ponera mealybug-carriers to the paleotropics ropyga captured with coccoids in their man- and the fact that this genus is monotypic sug- dibles reported here represent the oldest de- gest that Tetraponera is substantially younger ®nitive record of ant-homopteran symbiosis, than Acropyga. Likewise, the regional restric- although an earlier origination of such asso- tion of Dolichoderus herdsmen ants to South- ciations is likely (Grimaldi and Agosti, east Asia indicates that they, too, are younger 2000). Little is known about Cretaceous for- than Acropyga, albeit very successful. At least micines; however, the widespread use of ho- a dozen species of Dolichoderus tend more mopterans by almost all formicine genera than two dozen species of mealybugs (table 1). suggests that the relationship originated as early as the Cretaceous (Grimaldi and Agos- ti, 2000). Nonetheless, the primitive nature ACKNOWLEDGMENTS of the Cretaceous ants and the tendency of David Grimaldi (American Museum of Nat- most primitive living subfamilies of ants to ural History [AMNH]) made signi®cant con- be largely predatory and/or scavenging sug- tributions to the manuscript and provided the gest that the relationship between Cretaceous Harvard collection amber specimens, their ants and coccoids was not yet mutualistic, if photographs, and their identi®cations; Jan Ko- even obligatorily commensalistic, despite the teja (University of Krakow) provided identi®- probable widespread availability of honey- cations of some of the living and amber coc- dew in the Cretaceous. coids and comments on other published re- The oldest report of ant-homopteran sym- cords; Dan Janis (AMNH) produced the scan- biosis was based on a piece of amber contain- ning electron micrographs (SEMs); W. Dorow ing a group of Germaraphis aphids and 15 and J.-P. Kopelke provided excellent photo- workers of Iridomyrmex (Wheeler, 1915). graphs of the Frankfurt collection specimens; However, because Germaraphis aphids and Ir- and Phil DeVries shared some insight on hon- idomyrmex ants are common in Baltic amber eydew harvesting by ants. Roy Larimer gen- and are sometimes found grouped together, erously donated the Dominican amber piece Heie (1987) considered the assemblage of Ger- with the Azteca ants to AMNH. The original maraphis with Iridomyrmex in that piece to be manuscript greatly bene®ted from comments merely coincidental. Heie, furthermore, doubt- by Phil DeVries, Jan Koteja, Stefan Cover, Phil ed that aphids with strong wax production, Ward, and Jack Longino, to whom we are e.g., Germaraphis spp., had associations with grateful. We also thank two anonymous re- ants (personal commun. in Boucot, 1990: 477). viewers for their helpful comments. Nonetheless, HoÈlldobler and Wilson (1990) agreed with Wheeler's original conclusion that the two organisms were symbiotic. Although REFERENCES Wheeler's specimen is equivocal, an Eocene/ Agosti, D. Paleocene age of ant-homopteran symbioses is 1991. Revision of the oriental ant genus Cla- certainly expected, given the Miocene evi- domyrma, with an outline of the higher dence of intimate relationships between extant classi®cation of the Formicinae (Hy- ants and mealybugs. menoptera: Formicidae). Syst. Ento- Today, the genus Acropyga is distributed in mol. 16: 293±310. Central and South America, Europe, Africa, Agosti, D., and C. A. Collingwood Southeast Asia, and Australia. Inclusions of 1987. A provisional list of the Balkan ants this genus in amber, however, are known only (Hym. Formicidae) and a key to the worker caste. I. Synonymic list. Mitt. from Dominican amber, represented by two Schweiz. Entomol. Ges. 60: 51±62. clearly distinguishable species. No Acropyga Agosti, D., J. Moog, and U. Maschwitz species have been found in Baltic amber. From 1999. Revision of the Oriental Plant-ant ge- this, one might conclude that Acropyga did not nus Cladomyrma. Am. Mus. Novitates yet exist in the Oligocene and that the genus 3283: 24 pp, 35 ®gs., 2 tables. 2001 JOHNSON ET AL.: ACROPYGA AND AZTECA ANTS 13

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APPENDIX 1

Descriptions of a New Genus and Three New Species of Rhizoecinae (Hemiptera: Coccoidea) Associated with Ants of the Genus Acropyga Roger in Dominican Amber

D. J. WILLIAMS

The three mealybug species discussed here, found in Eumyrmococcus, Neochavesia, or Xeno- found in Dominican amber, belong to the subfam- coccus but the new genus is most closely related to ily Rhizoecinae and show a combination of char- Eumyrmococcus and Neochavesia. acters that have not been observed so far. Within In Rhizoecus KuÈnckel d'Herculais and most re- this subfamily, discussed recently by Williams lated genera, the antennae when developed, are (1998), most of the genera have the body elon- short, usually with the segments as wide as or gate-oval, rotund, or only weakly pyriform. Three wider than long. The antennae never have more genera, Neochavesia Williams and Granara de than 6 segments and this number may be basic to Willink, Eumyrmococcus Silvestri, and Xenococ- the whole subfamily. The new genus, therefore, cus Silvestri, differ in possessing a strongly dilat- with slender antennae having 6 segments that are ed cephalothorax and a long tapered abdomen. mostly longer than wide, may be a link between Furthermore, these three genera, Neochavesia in the Rhizoecus group of genera and the Eumyr- the New World, and Eumyrmococcus and Xeno- mococcus group. coccus in the Old World, are associated with the As with many specimens examined in amber, it is sometimes dif®cult to measure certain struc- ant genus Acropyga. Neochavesia differs from the tures exactly. Furthermore, it may be impossible two Old World genera in having protruding and to view the insect or structures in the correct plane rounded anal lobes and each antenna with 4 or 5 to examine them critically. segments. In Eumyrmococcus and Xenococcus, Apart from the piece of amber from Dominican each antenna has 2±4 segments and the anal lobes Republic containing a mealybug held in the man- do not protrude. Xenococcus possesses antennae dibles of an ant, presently deposited in Germany, that are stout and about as long as the body but three other pieces have been kindly made avail- in Eumyrmococcus they are slender and short. able for study by David Grimaldi, Division of In- To separate the genera of the Rhizoecinae, there vertebrate Zoology, AMNH. Two of these contain are other minute characters that can only be ob- mealybugs that are described here, but the third served under high power in slide-mounted speci- mealybug (Miocene, Dominican Republic, DR- mens. In the species under discussion, many of these 10-228 AMNH), held in the mandibles of a spe- characters cannot be observed when viewed under cies of Acropyga, is too distorted to examine and a stereoscopic microscope, and only some major describe adequately. characters can be discussed. Each of the three spe- Abbreviations of the depositories are: AMNH, cies found in Dominican amber, associated with ants American Museum of Natural History, New York, of the genus Acropyga, possess a strongly dilated NY, USA; SMF, Senckenberg Museum, Frankfurt cephalothorax. The abdomen tapers gradually to a am Main, Germany. very narrow posterior end. Although the anal lobes are undeveloped or weakly developed, each anal Electromyrmococcus Williams, new genus lobe area possesses 4 long setae. The antennae are TYPE SPECIES: Electromyrmococcus abductus, slender and 6-segmented. These are characters not new species. 2001 JOHNSON ET AL.: ACROPYGA AND AZTECA ANTS 17

DESCRIPTION: Body with cephalothorax dilated, abdomen gently tapering to narrow posterior segment. Posterior end straight with anal lobes not developed, or with slightly developed anal lobes, last segment with 2 groups of 4 long ¯agellate setae, these either spaced on ventral margins or grouped on anal lobes. Legs normal, slender; trochanter ϩ femur about as long as tibia ϩ tarsus; tibia and tarsus subequal in length; claw long and slender. Antennae about as long as legs, slender, 6-segmented, segments mostly longer than wide. COMMENTS: With a dilated cephalothorax and a long tapering abdomen, this genus appears to be related to the extant genera Eumyrmococcus and Neochavesia. It differs from the tropical New World genus Neochavesia in lacking rounded protruding anal lobes and from Eumyrmococcus, known from the tropical and temperate areas of the Old World, in possessing a group of 4 long setae in the position of each anal lobe. In Eumyr- mococcus, the long setae on each anal lobe form a group of 3 except in species with the long setae not differentiated from others on the lobes. The antennal segments in Eumyrmococcus number 2± 4 and in Neochavesia 4or5.InElectromyrmo- coccus, the antennae are long and slender, 6-seg- Fig. 8. Electromyrmococcus abductus Wil- mented, 300±365 ␮m long, longer than in many liams, new species a. Adult female, ventral aspect. species of Eumyrmococcus and Neochavesia. A Arrows point to area held by ant with mandibles. new species of Eumyrmococcus, however, is cur- b. Posterior segments, dorsal aspect. c. Posterior rently being described with antennae as long as 620 ␮m (Williams and Terayama, in press). segments, ventral aspect. d. Anal area. e. Claw. ETYMOLOGY: The name Electromyrmococcus is based on the Greek word elektron, as used for amber, myrmo- from myrmex, the Greek word for DESCRIPTION: This species differs from the other ant, and the generic name Coccus, referring to the two described here in having the long anal lobe ant-attended genus found in amber. setae spaced instead of grouped on each anal lobe. ETYMOLOGY: The epithet abductus is Latin for Electromyrmococcus abductus Williams, ``carried off'' in allusion to being held in the mandibles of the ant. new species Figure 8 Electromyrmococcus inclusus Williams and DESCRIPTION: Adult female about 0.7 mm long, Agosti, new species elongate-pyriform, cephalothorax dilated, abdo- Figure 9 men tapering gradually, segmentation distinct but segments not lobed laterally, segment VIII very DESCRIPTION: Adult female 0.76 mm long; ceph- narrow with anal opening slightly dorsal in posi- alothorax strongly dilated, about 0.46 mm wide; ab- tion, situated between barely perceptible anal domen tapering, abdominal segmentation well de- lobes; each lobe with 4 setae, each about 230 ␮m ®ned, each segment stepped to narrow segment long, equispaced laterally from tip of each lobe to VIII, 83 ␮m wide at base; anal opening dorsal at about half length of segment. Shorter abdominal apex. Abdominal segment II with a pair of dorsal setae present anterior to anal lobe setae on abdom- submedian projections. Anal lobes slightly devel- inal segment VIII, and in pairs arising laterally on oped, each with 4 long ¯agellate setae about 265 venter of preceding abdominal segments. Anten- ␮m long. Shorter setae present on lateral margins of nae each about 300 ␮m long, with 6 segments anterior segments. Antennae slender, each about 365 each longer than wide. Legs well developed, slen- ␮m long, with 6 segments. Legs well developed; der, about as long as antennae; tibia and tarsus hind trochanter ϩ femur about 165 ␮m long. subequal in length; claw long and slender. Holotype adult female, Dominican Republic, Holotype, adult female, Hispaniola: Dominican Miocene, Dominican amber, No. DR-14±403 Republic (Provincia de Puerto Plata), mine: La (AMNH). Toca (near La Cumbre), in mandibles of Acropyga DESCRIPTION: The specimen on which the de- sp. (M. von Tschirnhaus) (SMF). scription is based is distorted and has a deep con- 18 AMERICAN MUSEUM NOVITATES NO. 3335 striction between the thorax and abdomen. This Electromyrmococcus reginae Williams, constriction may have been caused by the ant new species holding the mealybug in the mandibles. Although Figure 10 the mealybug is detached, it is only about 650 ␮m from the mandibles, and the ant probably released DESCRIPTION: Body of adult female 0.80 mm long, it immediately when being trapped. After a cephalothorax dilated, abdomen gently tapering, ab- mealybug is held in the mandibles in life and then dominal segment VIII narrow, anal lobes very released, the body of the mealybug resumes its slightly developed, each with 4 long ¯agellate setae, normal shape, but the body in the specimen de- mostly about 265 ␮m long; segmentation of abdo- scribed, apparently had no such time. Further- men well de®ned, segments protruding postero-lat- more, it would be unlikely for any female mealy- erally to form lateral lobes so that segments appear bug to have a deep constriction between the tho- to be stepped. Antennae slender, each about 333 ␮m rax and abdomen because the ovaries in mealy- long, with 6 segments. Legs well developed and bugs are paired structures occupying almost the clothed in some setae, those on trochanters longest; hind tibia tarsus about 200 m long; claw long whole body cavity (Ali, 1959; Yadava, 1966). In ϩ ␮ and slender. Labium about 100 ␮m long, with long gravid females, the eggs or embryos completely setae at apex. ®ll the insect as far forward as the head and there Holotype, adult female, Dominican Republic, is never a constriction between the thorax and ab- in mandibles of a queen Acropyga sp. RL No. 6 domen to impede oviposition. The lateral lobes on (AMNH). the thorax were also probably caused by pressure DESCRIPTION: This species is closely related to of the ant's mandibles, resulting in distortion. E. inclusus in possessing long setae at the apex Electromyrmococcus inclusus possesses small of each anal lobe. The anal lobes of E. reginae, anal lobes that are more developed than in E. ab- however, are scarcely developed, whereas in E. ductus and E. reginae described here. inclusus they are more conspicuous. ETYMOLOGY: The epithet inclusus is a Latin par- ETYMOLOGY: The epithet reginae is based on ticiple meaning ``enclosed'' or ``imprisoned,'' refer- the Latin word regina in the sense of belonging ring to the specimen being trapped in the amber. to a queen; in this case a queen ant. novi 01209_01TQ Mp_19 File # 01TQ

Fig. 9. Electromyrmococcus inclusus Wil- liams and Agosti, new species a. Adult female, dorsal aspect. b. Cephalothorax, ventral aspect.

Fig. 10. Electromyrmococcus reginae Williams, new species a. Adult female, dorsolateral aspect. Ar- row points to area held by ant with mandibles. b. Posterior segment, dorsal aspect. c. Antenna. 2001 JOHNSON ET AL.: ACROPYGA AND AZTECA ANTS 21

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a This paper meets the requirements of ANSI/NISO Z39.48-1992 (Permanence of Paper).