E. O. Wilson and W. L. Brown, Jr.
Revisionary Notes on the Sanguinea and Neogagates Groups of the Ant Genus Formica.
Psyche 62:108-129, 1955.

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REVISIONARY NOTES ON THE SANGUINEA AND
NBOGAGA'TES GROUPS OF THE
ANT GENUS FORMICA1
BY E. 0. WILSON AND W. L. BROWN, JR.
Harvard University
In recent years, specialists engaged in ecological and regional studies of North American ants have repeatedly called upon us to check species identification against types and other "historic" material in the Museum of Compar- ative Zoology (MCZ). The specialist working away from such a collection is likely to assume that the difficulty can readily be cleared up by mere comparison of his fresh material against the Museum series; unfortunately, such comparison by itself rarely produces satisfactory results. Of the groups arriving at the MCZ, one causing repeated difficulty is the so-called subgenus Raptiformica of For- mica. In many ways, it exemplifies the current taxonomic conditions within many of our commonest groups of ants. The principal fault of the accepted Raptiformica ar- rangement lies in an excessive unrecognized synonymy, which in turn stems from past failure to appreciate the extent of allometric and other normal expressions of intra- specific variation. Species such as pergandei and rubicunda have been founded in large part on supposed differences in head shape, but closer examination shows these and other cases to be nothing more than size variants along the same general allometric gradient. Trivial variations in pilosity, sculpturing, and color have also 'been much overworked in separating "species" ; examination of enough material soon reveals most such variation as con- tinuously intergradient and broadly bridging the old gaps. Another situation bound to give continuing trouble in the future concerns the elusiveness of presumed sibling species such as F. parcipappa, F. curiosa and F. wheeleri - Published with a grant from the Museum of Comparative Zoology at Harvard College.




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19551 Wilson and Brown - Formica 109
we have been unable to find reliable and convincing char- acters marking the worker caste of these three forms. We are keenly aware that lack of material may have caused us to overlook other full but more or less cryptic species.
The original and present goals of this study are the elimination through synonymy of those names which can- not be supported by all available evidence, correction of certain inconsistencies in previous revisions (see literature cited at end of paper), and construction of a new key based on the present revision. After the majority of the work had been completed, however, another important consideration arose.
It had 'become apparent early in the task that Rapti- formica included two species-groups, termed by us respec- tively "sanguinea complex" and "obtusopiIosa complex." The sanguinea complex is distinguished by the follow- ing assem~blage of characters :
(1) The workers of all of the species usually have the masters black and the remainder of the body red, except F. parcipappa, which is concolorous reddish yellow. (2) The workers average large in size for Formica; are robust, and have a well-defined metathorax. (3) The propodeum is short, with a well-defined angle, and the petiolar scale is high and thin. (4) The gastric pubescence is dense and the body pilosity generally sparse. Hairs are never present on the dorsal face of the propodeum anterior to the propodeal angle. (5) The sculpture is generally opaque, or at most rather weakly shining.
(6) The male has relatively broad parameres" and a subgenital plate of a particular conformation (figs. 3, 5). (7) All of the species take slaves, at least facultatively, except F. pardpappa, which is known only from limited cabinet material.
(8) The complex as a whole prefers mesic habitats.



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110 Psyche [September
The obtusopilosa complex, perhaps wrongly named at the outset 'because obtusopilosa is the least typical and most poorly known of the species, offers the following characters :
(1) The worker coloration shows much interspecific variation, ranging from concolorous yellowish red to con- colorous black or red and black.
(2) The workers average smaller in size than in the sunguinea complex, are more slender in body form, and have a poorly defined metanotum.
(3) The propodeum is proportionately longer and more rounded, with little or no angle between dorsum and declivity.
(4) The gastric pubescence is very sparse (except in obtusopilosa) and the body pilosity generally abundant. Hairs are usually present, and often abundant, on the dorsal face of the propodeum anterior to the propodeal angle.
(5) The ~~culpture is usually feeble and the integument therefore more shining.
(6) The male has relatively slender parameres and a subgenital plate of a distinctive conformation (figs. 4, 6). EXPLANATION OF PLATE 11
Fig. 1. Head of F. subintegra woiker from University of Michigan Biological Station, Douglas Lake, Cheboygan Co., Mich. (P. B. Kan- nowski). Head width 1.71 mm. Fig. 2. Head of putative F. curiosa worker from Culbertson, Roosevelt Co., Mont. (E. 0. Wilson). Head width the same as in subintegra;specimen of fig. 1. Fig. 3. Left paramere å´o F. subnuda male from Woodland Park, Teller Co., Colo. (W. M. Wheeler). Fig. 4. Left paramere of F. perpilosa male from Ft. Davis, Texas (W. M. Wheeler). Fig. 5. Posterior border of subgenital plate of same specimen as in fig. 3 (F. subnuda). Fig. 6. Posterior border of subgenital plate of same specimen as in fig. 4 7. perpilosa). Fig. 7. Left side view of petiole of F. subintegra we from Rogers City, Presque Isle Co., Mich. (P. B. Kannowski). H .vidth 1.63 mm. Fig. 8. Left side view of petiole of F. subnuda w from Kiowa, Glacier Co., Mont. (E. 0. Wilson). Head width 1.76



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112 Psyche [September
(7) So far as is known, none of the species ever take slaves.
(8) The complex as a whole is limited mostly to xeric habitats in western North America.
The only species placed in the obtumpilosa complex with reservations is obtus~pilosa itself. In body form, pilosity, ethology, and habitat preference, it resembles the rest of the complex. But it also possesses coloration and gastric pubescence characteristic of the sanguinea complex. The male genitalia could add weighty and pos- sibly decisive evidence, but unfortunately no o btuwpilosa males seem to be available in any collection at the present time.
Both complexes share the clypeal notch character diag- nostic of Raptiformica, although in general this seems better developed in the sanguinea complex. Despite the presence of the notch, we felt that the two groups were very discrete from one another, casting doubt on the validity of Raptiformica as a natural grouping. At a late moment, we were led by a chance remark 'by Dr. Creighton (in Utt.) to reconsider certain views expressed to us in an all-but-forgotten letter received in 1953 from Dr. W. F, Buren. Buren's opinion then was that synonymy should bracket no less a pair of forms than Formica (Rap- tif ormica) hradleyi Wheeler and Formica (Prof ormica) neogagates var. morbida Wheeler.
Further, Buren implied
that the taxonomic standing of Raptiformica and the Nearctic representatives of Proformica is due for recon- sideration in the light of this synonymy2. Checking the type material involved in this important finding, we can only agree with Buren's suggested syn- onymy, which certainly will have a far-reaching effect in the simplification of the taxonomy of the genus Formica. We are not prepared to enter extensively into the taxonomy of the "Proformica complex'' at this time, 'but a few of our observations bearing on group interrelationships are offered as follows :
^ee Acknowledgements at the end of this paper.



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19551 Wilson and Brown -Formica 113
(1) In habitus of all castes of both sexes, and in details of worker-queen sculpture, pilosity, and form of propodeum and petiole, members of the obtwopilosa complex and the Nearctic species of "Proformica" (neogagates group) are obviously similar.
(2) The diagnostic Proformica character involving pro- portions of the first three funicular segments, never a very happy distinction, appears to grade through in the sanguinea-obtusopilosa series.
(3) The clypeal notch, supposedly characteristic of Raptiformica, is as well (or better) developed in many F. neogagates specimens as it is in those of some species customarily placed in Raptiformica (e. g. bradleyi, or even subnuda). The notch in neogagates and bradleyi is more properly described as a "vaulting" of the median clypeal margin as seen from an adoral view, 'but the effect is the same from full-face view, and the difference from the condition of subnuda is trifling, nsot to say academic. In neogagates, which appears to be a species distinct from bradleyi (= morbida) on the basis of color and pilosity characters, variation in clypeal vaulting is considerable. Most western samples show stronger vaulting, frequently equalling bradleyi, while some eastern samples have a flat- tened border like that of lasioides.
(4) The parameres and subgenital plate of the male in neogagates, bradleyi, and perpilosa are very similar (see figs. 4, 6).
(5) Many of the Palaearctic species of Proformica, in- cluding the subgeneritype F. nasuta Nylander, differ markedly from the Nearctic species (typified by neoga- gates) in characters involving degree of worker poly- morphism, and in worker-queen mandilbular dentition. In addition, the male genitalia are very distinctive in the one species, nasuta, in which males have been examined. These species seem to form a monophyletic group easily separated from the Nearctic neogagates group as well as from all Nearctic Formica.
Conclusions drawn from these facts are: (1) the obtu-



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114 Psyche [September
sopilosa complex is closest to, in fact coextensive with, the neogagates group (= Nearctic "Proformica") and probably has no direct connection with the sanguinea group; (2) the neogagates group, including the obtuso- pdosa complex, should be transferred to Formica s. sir.; (3) unless species annectant to Formica or Cataglyphis can be demonstrated, the true Proformica of the Old World, with nasuta as its type, probably rates full generic rank; (4) the subgeneric name Raptif ormica, having lost its morphological associations, should be put into synonymy until evidence is forthcoming for the need to recognize more than "species groups" in Formica.
The changes discussed in this work as they affect the old "Raptiformica" complex are outlined in the following synopsis. In this paper, only new synonymy will be cited formally; for additional synonymy and other references, see Creighton, 1950, pp. 460-472. 'The treatment of the sanguinea group here together with the obtusopilosa com- plex no longer implies natural connection between these two assemblages of species.
sanguinea group
curiosa Creighton
parcipappa Cole
saqptinea Latreille (with "varieties")
subintegra Emery
= pergandei Emery (n. syn.)
= puberula Emery (n. syn.)
= rubicunda Emery (n. syn.)
= sublucida Wheeler (n. syn.)
subnuda Emery (n. status)
= emeryi Wheeler (n. syn.)
wheeleri Creighton
obtusopilosa complex of neogagates group bradleyi Wheeler
= neogagates var. morbida Wheeler (n. syn., W. F. Buren in litt.)
manni Wheeler
= oregonensis Cole (n. syn.)




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19551 Wilson and Brown - Formica. 115
o b tusopilosa Emery
= obtusopilosa alticola Wheeler (n. syn.) perpilosa Wheeler
SPECIES IN THE SANGUINEA GROUP PROPER
In our study of sanguinea and relatives, we have been engaged chiefly with the Nearctic forms. It will be noticed that where Creighton recognized ten Nearctic species in the true sanguinea group, we retain only half that num- ber, and of these five names, we can recognize only two as representing solidly verified and distinct species: sub- Integra and subnuda. The three forms curiosa, parcipappa and wheeleri were all described from very limited material, and all are close to, if not synonymous with, the extremely variable subintegra. All three are western in distribution, and significantly it is in the west that subintegra reaches its peak variability, in an area where a wide range of differing habitats is available to influence variation. It is also possible that these slave-makers respond in some way to the characteristics of the available slave species of Formica, which in general are more diverse in the western part of North America.
As work on the sanguinea group progressed, we solicited the aid of several of our North American colleagues with respect to problems met. While comments and material received in the ensuing exchange were often very helpful, we have 'been surprised at the vigor of the opposition aroused by sonde of our synonymiic proposals. Unfor- tunately, the evidence for such opposed viewpoints did not match the conviction with which they were some- times expressed. Despite requests on our part for further particulars, we have received no evidence to indicate that anything is amiss with our synonymy. We are assuming that all important relevant data have now been forwarded for our consideration in the preparation of this paper. The couplet offered 'below will serve to separate workers of subnuda from those of subintegra.
A.
Gula completely bare of standing hairs in all of the workers of a nest series; dorsal petiolar margin



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116 Psyche [Septembe~
completely lacking hairs, or at most with one or two inconspicuous hairs less than 0.03 mm in length; hairs almost never present on propodeum; petiolar scale in side view nearly always thin and with a sharp crest (see fig. 7). (Boreal-alpine North America) ................................. subnuda Emery At least one or two long, coarse, standing hairs nor- mally present on the gula of a majority of the workers of a nest series; in those individuals with pronotal width of 1.0 mm or greater, and frequently in all of the nest members, the dorsal petiolar margin bears at least two or three hairs 0.05 mm or more in length; hairs frequently present on the propodeum at the junc- tion of the dorsal and declivitous faces; petiolar scale in view usually relatively thicker and with a blunt crest (see fig. 8). (Widespread in temperate N. America) ...................... subintegra Emery For comments dealing with the separation of curiosa, parcipappa, and w heeleri from subintegra, see the discus- sions under the individual species headings below. Formica sanguinea Latreille
Formica sanguinea Latreille, 1798, Essai Fourmis France, pp. 37-38 ; worker (widely distributed in temperate Eurasia).
We have had the opportunity to examine large numbers of series of this species from over most of its range. We have found it to differ with reasonable consistency from the cognate Nearctic species subnuda in the following worker characters :
(1) The clypeal notch is much deeper in sanguinea. The section of the clypeal margin enclosing the notch appears moderately concave when the head is viewed in perfect full face (at maximum length) ; in subnuda it usually appears flat or feebly convex.
(2) The 'body hairs are longer and more abundant in sanguineu.
At least four or five standing hairs project



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19551 Wilson and Brown - Formica, 117
beyond the dorsal margin of the pronotum seen from the side; in subnuda at most three or four are visible in this view, and usually less.
(3) The head of sanguinea is always infuscated, and on the average more deeply than in subnuda, although there is some amount of overlap in the total variation of the two species.
Despite the completely allopatric distribution of san- guinea and its obvious cognate relationship to subnuda, we are treating the two forms as distinct species. The reason is that they differ by at least two discontinuous characters, while the total morphological difference is ap- parently greater than that separating some of the sym- patric Nearctic species. 'Thus, in the absence of direct evidence concerning their status, reliance is placed on an arbitrary, morphological "species-standard" method in order to insure uniformity of treatment throughout the species group.
The intermediate position of sanguinea between subnuda and subintegra with respect to the pilosity and clypeal not'ch characters described above may represent another case of the phenomenon of '',character displacement" as recently described in the genus Lasius by Wilson (1955). Our interpretation would be that subnuda remains well segregated morphologically from subintegra because it is partly sympatric with it, and as a result the two species tend to occupy ecologically different "niches." As a distinct species and the Palaearctic equivalent of subnuda, san- guinea has no such competitor, and therefore presumably converges morphologically toward subintegra in filling the adaptive vacuum which a companion species might other- wise occupy.
We have mad,'e no attempt to treat the Palaearctic "varieties" of sanguinea in the present study. Most of these are based on color differences and do not seem on cursory examination to be strong candidates for species rank. We have included in our diagnosis of sanguinea varietal material from the following several localities: Guadarrama, Spain (C. Schramm leg. ; var. flavorubra



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118 Psyche [September
Forel, det. W. M. Wheeler) ; Lake Sevan, Armenian S. S. R. (F. Arnoldi leg.; var. clarior Ruzsky, det. Arnoldi and B. Finzi) ; neighborhood of Kiev (W. Karawajew leg. ; 44 var. clara" Karawajew, ms?) ; "Ussurigebiet", Soviet Maritime Territory (var. orientalis Ruzsky, det. Karawa- Jew) ; Kedzovajapadj, near Vladivostok (N. Kusnezov leg.; var. clarior Ruzsky, det. Kusnezov) .
Formica subnuda Emery (figs. 3, 5, 8)
Formica sanguinea rubicunda var. subnuda Emery, 1895, Zool. Jahrb. Syst., 8: 335; worker. Type locality: Yale, British Columbia.
Formica sanguinea subnuda, Wheeler, 1913, Bull. Mus. Comp. Zool. Harv., 53: 409. Creighton, 1950, Bull. Mus. Comp. Zool. Harv., 104: 469.
Formica emeryi Wheeler, 1913, Bull. Mus. Comp. Zool. Harv., 53 : 419; worker, queen. Type locality: Broad- moor, Colorado Springs, Colo. NEW SYNONYMY. This is the most boreal and widespread of the North American members of the sanguinea group. Its affinity to the Palaearctic sanguinea is evidenced by the form of the petiolar scale, pilosity, 'body coloration, and degree of intranidal size variation, as well as its similar ethological characteristics. The characters which separate the two species have already been presented in the section on san- guinea, above. F. subnuda, like F. sanguinea,, is only facultatively a slave-maker.
Even when taken, the slaves
frequently form only a small percentage of the nest popula- tion, (Wheeler, "Ants," p. 454; 'Creighton, 1950, p. 469). A single worker and three queens from the emeryi type series that we have examined conform to subnuda in critical pilosity characters. Other differences advanced by past authors as diagnostic for emeryi have proven to be worthless. To avoid future confusion these are discussed in some detail below.
(1)
Emeryi has been distinguished from subn2~du (by Creighton) on the contention that in the largest workers the eyes extend to the margin of the head seen in full



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19551 Wilson and Brown - Formica 119
face. As previously noted, this is a character subject to strong allometric variation. The subnuda types we have examined in the same size class as the emeryi syntypes (head widths 1.41 - 1.64 mm) exhibit the same head shape and eye placement, and this also holds for other subnuda series.
(2) Wheeler and ~Creighton both have distinguished emeryi from subintegra (= pergandei) by the presence in emeryi of a shallow transverse groove on the dorsal propodeal face of the worker. In this case the wrong pair of species was being compared, but the character must also lbe considered with reference to subnuda. Of the four subnuda syntypes we have examined, three possess the character and one lacks it. Other subnuda and sub- htegra series show the same strong intrandidal variation, and we are of the opinion that the propodeal impression is either an ecophenotypic character or else an artifact produced by warping when the specimens were first dried out. In any case, it is not diagnostic.
(3) The genal borders of the emeryi syntype are nearly straight, and where they meet the curved olccipital border near the lower margin of the eye a weak concavity is produced. This is not so common a feature of subnuda, but is nevertheless within the normal range of variation for the species. One specimen of a series from Magnolia, Mass., shows the "emeryi" contour on one side and the typical subnuda contour on the other.
(4) The emeryi worker and queen syntypes actually differ the most from average subnuda in a character not mentioned by previous authors.
The petiolar scale in side
view is unusually thick for subnuda, approaching the usual subintegra condition, 'but even this is still within the range of continuous variation of subnuda as we eon- ceive of that species.
F. subnuda definitely has a more boreal distribution than does F. subintegra, though the ranges of the two species come into close contact and even overlap in regions