Acropyga and Azteca ants (Hymenoptera, Formicidae) with scale insects (Sternorrhyncha, Coccoidea) : 20 million years of symbiosis

20 Pages·2001·2.5 MB·English

by  Johnson, Christine

AMERICAN MUSEUM
Novtitates
PUBLISHED BY THE AMERICAN MUSEUM OF NATURAL HISTORY
CENTRAL PARK WEST AT 79TH STREET, NEW YORK, NY 10024
Number 3335, 18 pp., 10 figures June 22, 2001
Acropyga and Azteca Ants (Hymenoptera:
Formicidae) with Scale Insects (Sternorrhyncha:
Coccoidea): 20 Million Years of
Intimate Symbiosis
CHRISTINE JOHNSON,! DONAT AGOSTI,? JACQUES H. DELABIE,?
KLAUS DUMPERT, D. J. WILLIAMS,* MICHAEL VON TSCHIRNHAUS,*> AND
ULRICH MASCHWITZ?
ABSTRACT
Species of the genus Acropyga are rarely encountered subterranean ants that rely on mealy-
bugs 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 first 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 signifi-
cance of these specimens in Dominican amber is discussed.
INTRODUCTION a variety of arthropods (reviewed in Hdll-
dobler and Wilson, 1990). The trophobiotic
Of the numerous symbiotic relationships
associations, which involve the trophobiont
known from animals, few are as impressively
providing nutrient-rich excretions or secre-
intimate as those that occur between ants and
' Scientific Assistant, Division of Invertebrate Zoology (Entomology), American Museum of Natural History.
? Research Associate, Division of Invertebrate Zoology (Entomology), American Museum of Natural History.
3 Professor, Fachbereich Biologie und Informatik der Johann Wolfgang Goethe Universitat, Frankfurt/Main, Ger-
many.
4 Department of Entomology, Natural History Museum, London.
> Professor, Fakultat fuer Biologie, Universitat Bielefeld, Bielefeld, Germany.
Copyright © American Museum of Natural History 2001 ISSN 0003-0082 / Price $2.70
2: AMERICAN MUSEUM NOVITATES NO. 3335
TABLE 1
Species of Dolichoderus Herder Ants and of Allomyrmococcini Mealybugs Herded, and Region
Dolichoderus spp. Allomyrmococcini spp. Region
D. coniger Malaicoccus sp. E4 Borneo (Sabah: Poring)
D. coniger M.sp.L Borneo (West Sarawak)
D. cuspidatus M. formicariz W. Malaysia (various areas)
D. cuspidatus M. moundi W. Malaysia (Genting Highl.}
D. cuspidatus M. riouwensis North Sumatra
D. cuspidatus M. takahashti W. Malaysia (South)
D. cuspidatus M. sp.B W. Malaysia (Bukit Larut)
D. cuspidatus M. sp.D Borneo (East Sarawak)
D. cuspidatus Genus | sp. A Borneo (Sabah: Poring)
D. cuspidatus Genus 6 sp. A Borneo (West Sarawak)
D. cuspidatus Genus 6 sp. B Borneo (West Sarawak)
D. erectilobus Paramyrmococcus chiengraiensis Thailand
D. feae Allomyrmococcus acariformis Thailand
D. furcifer Genus 5 sp. A West Sumatra
D. gibberifer Hippeococcus wegneri West Java
D. tuberifer Malaicoccus khooi W. Malaysia (Genting Highl.)
D. tuberifer M. sp. F Sumatra (West Sumatra)
D. tuberifer M. sp.G W. Malaysia (Southeast coast)
D. tuberifer M. sp. H W. Malaysia (Cameron Highl.)
D. tuberifer M. sp. 1 W. Malaysia (Pahang)
D. sp. A Genus 2 sp. A Borneo (Sabah: Poring)
D. sp. B Genus 4 sp. A Borneo (Sabah: Poring)
D, sp. C Genus 2 sp. B Borneo (Sabah: Kinabalu HQ)
D. sp. D Genus 3 sp. A Borneo (Sabah: Poring)
D. sp. E Genus 6 sp. C Borneo (West Sarawak)
4Provisional numbers and letters refer to genera or species to be scientifically described and named (from Dill and Maschwitz,
1998).
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; Hodlldobler 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 fission and the workers bring with
by stroking them. them a self-contained colony of mealybugs
The many thousands of species of scales (Maschwitz and Hanel, 1985; Dill and Mas-
(Coccoidea), greenflies (Aphidoidea), white- chwitz, 1998, Maschwitz and Dill, 1998).
flies (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
(o_n_™) Rhizomyrma
C_) Acropyga
i"; Atopodon
© Malacomyrma
Fie. cl. 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 (Biinzli, 1935). There are two kinds of gal-
Southeast Asian ant Tetraponera sp. near at- leries, or chambers, in Acropyga ant nests
tenuata FE Smith (Pseudomyrmecinae) and of (Biinzli, 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 EK 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 Roget. a relatively well-defined geographic distri-
Colonies of Acropyga species that tend pseu- bution (see fig. 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 Biinzli are oblig-
1944); in cacao, coffee, and banana planta- atory coccoidophiles that tend Pseudococci-
tions (Biinzli, 1935; Weber, 1944); and in dae from a total of four genera. Acropyga
grassy pastures (Weber, 1944; Eberhard, paramaribensis tends five 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 difficult 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 flight 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 flights, 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 figure 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 (fig. 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 significance the treatment by Weber (1944). It is quite
of finding scale insects together with ants in possible that this ant is one of the two species
amber is discussed. of Acropyga reported by Biinzli (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 flights
Observations and samples were taken by C. are mated females; however, others may be
Johnson in central French Guiana (3°38'N, unmated females or even immature males
53°13'W, approx. 300 m elevation) on Decem- that resemble females (Biinzli, 1935). In ei-
ber 26, 1996, near the town of Saiil, 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 (Biinzli, 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 dish-
es (fig. 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)
Acropyga
Mealybug Species Rhizoecini (Rhizomyrma) sp. Country Reference
Neochavesia® sp. x A. berwicki Trinidad Wheeler, 1935; Weber, 1944
Neochavesia sp. x A. decedens Brazil Delabie, unpublished
Neochavesia® sp. X A. donisthorpei Guyana Weber, 1944
Neochavesia® sp., possibly eversi> xX A. fuhrmanni Colombia Roba, 1936; Weber, 1944:
Flanders, 1957
Neochavesia® sp. xX A. goeldi Brazil Weber, 1944
Neochavesia® sp. x A. near paramaribensis Brazil Delabie et al., 1989
Neochavesia caldasiae xX A. robae Colombia Balachowsky, 1957
Neochavesia eversi x A. kathrynae Panama Beardsley, 1970
Neochavesia weberi x A. paludis Guyana Weber, 1944; Beardsley, 1970
Geococcus coffeae x A. decedens Brazil Delabie et al., 1989
Encarnacao et al., 1993
Geococcus coffeae x A. urichi Brazil Encarnacao et al., 1993
Geococcus coffeae x A. paramaribensis Surinam Biinzli, 1935
Rhizoecus coffeae x A. decedens Brazil Goeldi, in Wheeler, 1935
A. paramaribensis Surinam Biinzli, 1935; Weber, 1944
Colombia Roba, 1936
A. pickeli Brazil Borgmeier, 1927; Weber, 1944
Dysmicoccus radicis — A. rutgersi Surinam Biinzli, 1935
Pseudorhizoecus sp. xX A. wheeleri Costa Rica = Weber, 1957
Capitisetella migrans xX A. rutgerst Guyana Biinzli, 1935
Surinam Biinzhi, 1935
Pseudorhizoecus proximus Xx A. paramaribensis Surinam Biinzli, 1935
A. rutgersi Surinam Biinzli, 1935
Rhizoecus sp. x A. decedens Brazil Delabie et al., 1989
Rhizoecus caladti x A. paramaribensis Surinam Btinzli, 1935
Rhizoecus fatcifer Kiinckel d’ Herculais x A, paramaribensis Surinam Biinzli, 1935
Unidentified a Acropyga sp. Colombia Eberhard, 1978
Unidentified ? Acropyga sp. Brazil Campos and Morais, 1986
Unidentified ? A. bruchi Argentina Weber, 1944
Unidentified ? A. guianensis Guyana Weber, 1944
Unidentified ? A. mesonotalis Haiti Weber, 1944
Unidentified ? A, guadriceps Trinidad Weber, 1944
Unidentified ? A. trinitatis Trinidad Weber, 1944
Unidentified ? A. urichi Trinidad Weber, 1944
4 Identified in the literature as Eumyrmococcus prior to the Balachowsky (1957) and Beardsley (1970) papers.
b See Beardsley (1970).
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 an-
terior margin); antennae 9-segmented. Prono-
tum very short; mesonotum much higher than
pronotum, nearly flat on top, as long as wide,
with rounded corners. Gaster more than | 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 oc-
ciput. Mandibles long and narrow; antennae
10-segmented; scapes projecting beyond occip-
ital margin. Ocelli protruding considerably. Al-
itrunk only slightly broader than head width;
Fig. 2. Acropyga from Saitil, 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 profile 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 (fig. 5c); her
contemporaneous with the other Dominican
cuticle and that of the scale insect are slightly
amber pieces. Roy Larimer provided the fifth
distorted by compression. Specimen AMNH
amber piece, which contains workers of Az-
DR-14-403 (fig. 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 (fig. 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.
(figs. 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 (fig. 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 (fig. 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 X 2.8 X 1.1 cm) contains 9 workers
Frankfurt collection (fig. 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 cecidomyliid midge (fig. 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
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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 abdom-
inal 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, person-
al commun.).
It is, however, almost certain that these
coccoids were tended by the ants, even
though none of the workers is actually car-
rying a mealybug. Azteca species, like most
dolichoderines, are renowned for tending ho-
mopteran 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 in-
clusions, coccoids, particularly nymphs, are
extremely rare. The chance of finding 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 infinitesimally small, as is the chance
drawn from Prins [1982] by Williams [1993]). of finding a fortuitous cluster of coccoids and
Azteca alpha ants. The presence of males and
females coccoids at several developmental
phology is much more generalized than the
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 (40-50) of an Acropyga gyne from Saiil, 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 definitive 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,
1988), apparently Paleocene in age, whereas
Fig. 6. Mealybug (detail) in amber (Harvard
several taxa are described from Eocene Arkan-
collection piece, AMNH DR-14-403).
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 am-
ber 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 (Brandao 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