Wm. S. Creighton.
Pseudomyrmex Apache, a New Species from the Southwestern United States (Hymenoptera: Formicidae).
Psyche 59:131-142, 1952.

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PSEUDOMYRMEX APACHE, A NEW SPECIES FROM
THE SOUTHWESTERN UNITED STATES
(HYMENOPTERA : FORMICIDAE)
BY WILLIAM S. CREIGHTON
Department of Biology, College of the City of New York The majority of the material on which this paper is based was secured during 1951 and 1952. At that time the writer was engaged in a field survey of the ants of the border region. This work was made possible by a fellowship from the John Simon Guggenheim Memorial Foundation. My sincere thanks go to the Foundation for the support which made this work possible.
The taxonomy of the genus Pseudomyrmex presents an unusual number of difficulties. Even the generic name has not escaped the hazard of uncertainty. The name Pseudo- myrma, which has been accepted for more than a century, has recently been challenged. Twice in the past two years Dr. M. R. Smith has introduced prior names for the genus. The latest choice is Psevdomwmex Lund which, on the basis of data presented by Dr. Smith in 1952 (Proc. Ent. Soc. Wash., Vol. 54, No. 2, p. 97) has a priority of thirteen years over Pseudomyrma Guhrin. But any difficulty with the generic name is a minor matter in contrast to the de- plorable incertitude which marks a large number of the species in this genus. The taxonomy of many of them is in such confusion that specific recognition is largely a matter of guess-work. With this fact in mind, the writer has hesitated for some time to describe the material treated here. It would seem, however, that we can no longer avoid dealing with this material for, whatever its taxonomic status may be, it is certain that its presence in the south- western United States has not previously been recognized. It is prdbacble that the older records for this ant have been attributed to Ps. pallida. The two insects are superficially Published with a grant from the Museum of Comparative Zoology at Harvard College.




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132 Psyche [December
simflar and they occur in the same stations in the southwest. As long as it was believed that only pallida, occurred in this area, there was little reason to suspect the existence of a second species.
The writer first encountered Ps. apache in 1932. In Sep- tember of that year a single, dealated female was taken in Ramsey Canyon in the Huachuca Mountains of Arizona. This insect had a clear, yellow coltor similar to that of Ps. pallida, but it differed from the female of pallida in its much greater size and in a number of other structural features. Since no workers were associated with the above female, its status was problematical and it was not included in my 1950 monograph on North American ants. In the spring of 1949, after that paper hlad 'gone to press, Dr. L. F. Byars sent me a number of workers of a large, yellow Pseudomyrmex which had come from three colonies taken in southern Arizona. These seemed to be the same species as the female from Ramsey Canyon, but this was not veri- fied until the following summer. In 1950 a colony contain- ing all three castes was taken by the writer in Garden Canyon in the Huachuca Mountains. Since that time the writer has secured forty-five additional colonies of this ant in fifteen different stations. These stations extend from the Brownsville area of Texas to the mountains of southern California. It is clear that this ant is abundant in the southwestern United States and some cognizance must be taken of it. The difficulty is to decide how this insect should be treated.
The writer first believed that this ant represented Ps. decipiens or a northern race of it. Dr. W. M. Wheeler had identified as decipiens a series of specimens taken in Costa Rica. These specimens were similar to those coming from the southwestern United States but there were several dif- ferences, particularly in the shape of the petiole. In 1949, when the above comparison was made, there was not enough material to evaluate these differences. As a result the writer told Dr. Byars that the insect probably represented some form of decipiens, but that no certain statement could be made until more data was available. In the meantime the writer attempted to discover how Dr. Wheeler had identi-



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19521 Creighton - Pseudomyrmex apache 133 fied the Costa Rica specimens. As far as could be ascer- tained there are no types of decipiens in American collec- tions.
Nor do there seem to be any specimens other than types which Forel might have determined. Apparently Dr. Wheeler used Forel's dlelscription as the basis for his identification and, as will be shown, this is a bad business at best. The original description of decipiens appeared in the ant section of the Biologia Centrali-Americana. It was based upon specimens coming frlom Teapa, a small town in the state of Tabasco, Mexico. The description is brief, but this is not the worst than can be said for it. It is suffi- ciently explicit to show that it does not accord in several important respects with the figure which is supposed to accompany it. These differences are so marked that there is Justification for the view that the description and the figure can scarcely have been drawn from the same insect. In the figure the size of the eyes, the length of the antenna1 scapes and the proportions of thce petiolar joints do not correspond at all to the description. Fore1 did not prepare the figure but he undoubtedly wrote the description, hence the latter seems more reliable as an indication of the characteristics of decipiens. Wheeler had evidently reached this conclusion, for his C'osta Rica specimens agree much better with Forel's dlescription than with hils figure. But it should be clear that there can be no certainty as to the exact nature of Forel's decipiens until the types can be re-examineid.
At the same time it seemed to the writer that it should be possible to clarify the status of specimens coming from the southwestern United States by colllecting in northern Mexico.
If the southwestern specimens were a northern race of decipiens, the two should intergrade at som'e point between Tabasco and the southern border of the United States. The survey work mentioned above gave an ideal opportunity to test this in the field. During January and February of 1952 careful vertilcal surveys were made in the mountains of eastern Mexico at three latitudes. The southernmosit of these was in the Tamazunchale area. This survey ranged from three hundred feet to eight thousand feet. Similar studies were made in the mountains west of



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134 Psyche [December
Linares (1300-6200 feet) and in those south and west of Monterrey (2000-7200 feet). By this time it was apparent that Ps. apache prefers to nest in old live oak limbs. Many hundred limbs of live oaks were examined in the areas mentioned above. While three different species of Pseudo- myrmex were encountered in these limbs, none of them showed the slightest relation to apcwhe. The coastal plain was less thoroughly studied, but collections made in the area between Mante and Tampico showed no trace of apche. The only abundant Pswidomyrmex in that area is a particularly vicious, light brown species which lives in the thorns of the bull-horn Acacia. In northwestern Mexico the situation is essentially similar. Ps. apache is abundant in the mountains at the northern end of the main chain of the Sierra Madre Occidental. But the writer failed to find it in several lesser ranges in northern Sonora. It may be added dhat in some of these ranges the conditions seemed ideal for this ant and the writer felt certain that it would be found. Negative evidence of this sort does not prove the absence of Ps. apache in the areas mentioned above, but it does prove that the insect is less abundant in these areas than in stations further north. This would not be true if this ant were a northern fringe of some southern species, for in that case its incidence should increase to the south. But, since all available evidence points to the fact that the area of greatest abundance for this ant lies in southern Arizona and that its incidence decreases to the south, it is safe to (wnclude that the insect is not a northern race of decipiens but a separate species.
Since all three castes have been figured on the plate which accompanies this article, the descriptive material which follows is largely limited to details of sculpture and pilosity that could not be shown in the figures. Pgeudomyrmex apache sp. nov.
Plate 12
Female : head (mandibles excluded) 1.35 mm. ; thorax 2.2 mm.; overall length 7-8 nun.
Upper surface of the head covered with small, shallow, circular punctures. These punctures close set from the anterior margin of the head to the level of the median ocel-



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1952 J Creighton - Pseudomyrmex apache 135 lus. From that level to the occipital border the punctures are much more widely spaced with the surface between them delicately coriaceous or reticulate and very feebly shining. The punctures on the genae and gula are notably smaller and more widely spaced than those on the front of the head. Both genae and gula are feebly shining. Clypeus and frontal lobes without distinct punctures and rather strongly shining. Mandibles with coarse, oval, piligerous punctures, the surface between them finely shagreened. Antenna1 scapes with numerous fine punctures, their sur- face more shining than the front of the head but less shining than the frontal lobes. Punctures on the thorax smaller, more shallow and more widely spaced than those on the front of the head, the surface between the punctures with a very delicate, reticulate sculpture. Pronotum and epinotum fedb'ly shining. Sicultulm, scute~llu~m, mesothoracic sternite and episternite a little more strongly shining. Punctures on the petiole very sparse and fine. Pos'tpetide and gaster with only a few, scattered, piligerous punctures. The delicate coriaceous sculpture becomes feebler as one passes from the petiole to the gaster and the parts become progressively morle shining, with the gastric segments par- ticularly so. Flore femora laterally compressed. Middle and hind femora not laterally compressed. Broth femora and tibiae with numerous, very small punctures which do not dull the shining surface.
Erect hsairs rather sparse over most of the body. Man- dibles and antennlal scapes with moderately numerous, short, erect hairs. Those on the upper surface of the head and on the gula much sparser, widely separated and very irregular in length. D'orsum of the pronotum with six or eight erect hairs. Scutum and scutellum with about a dozen erect hairs of varying lengths. Epinotum without erect hairs. Petiolle and postpetiole with eight or ten erect hairs each. These hairs are often, but not always, confined to the posterior half of each node. Erect gastric hairs largely confined to a broad band at the rear edge of each segment. Legs virtually devoid of erect hairs, except for one or two on the fore coxae and the fore femora. Tarsal joints and antenna1 funiculi densely covered with fine, semi-erect hairs



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136 Psyche [December
which grade into pubescence. Pubescence elsewhere very fine and so sparse that it is not usually noticeable except under considerable magnification or in very oblique light. Color: clear, golden yellow, the inner border of the man- dibles blackish brown. Edges of the thoracic sclerites and gastric segments a slightly deeper brownish yellow than the rest of the surface. Wings slightly iridescent, faintly tinged with yellow, the veins a deeper yellow, the stigma brown.
Male: head (mandibles excluded) 1.0 mm.; thorax 2.0 mm. ; overall length 6.5-7.0 mm.
Upper surface of the head finely coriaceous and feebly shining except for the area between the median ocellus and the antenna1 insertions, where the coriaceous scu1pture is largely replaced by fine punctures. Mandibles a little more heavily sculptured and less shining than thle rest of the head. Antennae finely and densely granulose, opaque. Lateral portions of the pronotum feebly coriaceous, less shining than the median portion which is covered with rather coarse, scattered punctures. Scutum and scutellum heavily coriaceous and dull except for an irregular, shining band down the middle of each. This band is coarsely punctate and very feebly coriaceous. Epinoltum feebly coriacems and rather strongly shining above, more heavily coriaceous and punctate on the sides. Mesothoracic sternite strongly shin- ing and coarsely punctate, the episternite feebly coriaceous and strongly shining. Petiolar nodes feebly shining and weakly coriaceous. The gaster very feebly sculptured and much more shining than the petiolar nodes. Erect hairs present 'on the ocellar area of the head, the scutum and the scutellum. Dorsum of the epinotum, the petiolar nodes and the dorsum of the anterior gastric seg- ments with one or two erect hairs each at most, often hair- less. Dorsum of the terminal gastric segment with several erect hairs. There are numerous erect hairs, which form -- - - - - - -
.- - - --
EXPLANATION OF PLATE 12
Pseudcmyrmex apache sp. nov. Fig. 1. Female, profile view. Fig. 2 Worker, profile view. Fig. 3. Head of female. Fig. 4. Petiole and post- petiole of worker, from above. Fig. 5. Head of worker. Fig. 6. Hezd of male. Fig. 7. Male, profile view.




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138 Psyche [December
a distinct fringe, at the ventral edge of each gastric seg- ment. Eyes with a number of short and extremely fine erect hairs. Mandilbles with numerous, coarse, erect, or semi- erect hairs. Pubescence abundant and fully appressed on the rear half of the head, semierect on the anterior half and on the gula. Pubescence on the thorax and the petiolar nodes much more dilute than on the head. Pubestence extremely dilute on the dorsum of the gaster but more abundant on its sides and ventral surface. Antennae and tarsi with abundant, short, appressed or semierect hairs which grade into pubescence. Femora and tibiae with less abundant pubescence than the tarsi.
Color: thorax, gaster, legs and antennae dirty yellowish brown. T1he scutum and the head a darker, more piceous brown. Mandibles dingy yellow. Wings pale, yellowish brown, the veins and stigma darker.
Worker : head (mandibles excluded) 1.15 mm. ; thorax 1.5 mm.; overall length 5-6 mm.
Upper surface of the head covered with circular punc- tures, as in the female, but with the coriaceous sculpture between the punctures much less pronounced, particularly on the rear half of the head. This gives the surface a slightly more shining appearance than in the female. Man- dibles much smoother than those of the female, the piliger- ous punctures notably smaller and, for the most part, circular or nearly so. Punctures on the thoracic d'orsum obscured by the even, coriaceous sculpture. This sculpture is also present on the sides of the thorax. Both dorsum and sides of the thorax feebly shining. Sculpture of the petjolar nodes and the gaster the same as in the female. Fore femora much less laterally compressed than in the female, not greatly different in shape from the middle and hind femora. The fine, coriaceous sculpture on the appendages more distinct than in the female, often obscuring the punctures, hence the legs are less shining than in the female. Pilmosity on the head very similar to that of the female. Erect hairs on the thoracic dorsum, when present, sparse and confined to the pronotum and mesonotum. A few erect hairs are present on the petiole, the postpetiole and the dorsum of each gastric segment, especially the last. Pube-



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1952 J Creighton - ,Pseudomyrmex apache 139 scence fine and obscure, very dilute on the head, more abundant on the thorax? petiolar nodes and gaster, but nowhere conspicuous.
Color : unif arm? clear? golden yell'ow. In some specimens the posterior gastri'c segment is slightly inf uscated. Types of female? male and worker deposited in the col- lection of the Museum of Comparative Zoology, Cambridge? Mass. ; the type locality is Brown Canyon (44001), Baboqui- vari Mts., Arizona. Type nest taken on Sept. 2, 1951, in Quercus o blongi f olia.
Because of ilts clear, yellow colsor and dilute pubescence apache is not likely to be confused with any of our other species except pdlida. There is little likelihood of confusion between these two species if all castes are present, for apache is larger than ~ 1 1 ~ and this difference is partic- ularly striking in the sexual forms. Workers from young nests of apache are? however, sometimes no larger than those of pallida. In such cases recognition depends upon other criteria which will separate the two species regard- less of size. Thus 'the worker of apache is more heavily sculptured than that of pallida, particularly on the upper surface of the head. In apache the cephalic punctures and the delicate? coriaceous sculpture between them can be readily seen? even under medium magnification? and the surface of the head is feebly shining. In pallida the cephalic sculpture is notably finer. The punctures are scarcely dis- tinguishable from the sculpture between them? even under high magnification? and the surface of the head is moder- ately shining. The head of apache is broader in proportion to its length, with the sides more convex than is the case with pallida. The greatest length of the eye in apache is slightly less than one half the distance from the insertion of the mandible to the occipital margin. In pallida the greatest leng$hs,:of the eye is slightly more than one half the above distance. The petiolar node of apache, seen in profile has a broadly rounded crest, from which both the anterior and the posterior face slope away at about the same angle. Thus the outline of the node appears as a flattened and slightly lopsided arc. In pallida the rear face of the node of the petiole descends much more abruptly



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140 Psyche [December
than the front face, hence, in profile the node presents a wedge-shaped rather than an arcuate outline. The distributional records for apache are presented be- low. Unless otherwise noted all specimens were taken by the writer. The elevations of the majority of these records were checked with topographic sheets and an altimeter, the remainder with one or &he other.
ARIZONA :
Huachuca Mountains : Ramsey Canyon (5500') single dealated female ; Garden Canyon (5800') three colonies in Quercus emoryi; Carr Canyon (5400') two colonies in Q. emoryi.
Santa Rita Mountains: Madera Canyon (5900') one col-
ony in Q. emoryi; Sweetwater (5800') three colonies in Q. emo~yi.
Dragoon Mountains : Cochise Stronghold (5200') one colony in Q. emorgi.
Chiricahua Mountains : Chiricahua National Monument (5400') one colony in Q. emorgi.
Peloncillo Mountains : Cottonwood Canyon (4800') two colonies in Q. ernoryi.
Baboquivari Mountains : Baboquivari Canyon (3500') one colony in Q. oblofigifoliu; Brown Canyon (4200- 4400') type locality, nine colonies in Q. emoryi or Q. oblongif olia.
Ajo Mountains: (Organpipe Cactus National Monument) Alamo Canyon (2200-2800') ten colonies, eight in Prosopis julif lora, two in Q. turbinella. Growler Mountains: (Organpipe Cactus National Monu- ment) La Abra Wash (1300') two colonies in Prosopis julif lora.
Cane10 Hills: Cane10 Pass (5300') one colony in Q. emoryi.
Pena Blanca Springs (3900') Santa Cruz Co. Coll. L. F. Byars, one colony without data on nest site. San Miguel (2400') Pima Co. Coll. L. F'. Byars, one col- ony in Prosopis julif lora.
Organpipe Cactus National Monument Headquarters (1650') Coll. E. R. Tinkham, one colony, said to have been taken emerging from a rodlent's burrow!



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19521 Creighton - Pseudomyrmex apache 141 CHIHUAHUA :
Sierra de en Medio: Nogales Ranch (5000') five colonies in Q. emoryi or Q. oblongifolia.
TEXAS :
Fowlerton (300') La Salle Co., one colony in Prosopis juliflora; Monte Alto (60'1, Hidalgo Co., two colonies in P. julif lora.
CALIFORNIA :
Agua Tibia Mountains : Dripping Springs (1500') two colonies in Q. chrysolepis.
The records cited above show that Ps. apache occurs most frequently in mountain~us areas at elevations between 2500 and 6000 feet. In sukh stations it ordinarily nests in evergreen oaks but, when the range descends below the oak belt, it will nest in mesquite. Whether the ants nest in oak or mesquite they select a good-sized branch or the trunk of the tree as a nest site. They seldom nest in twigs and this response is striking in view of the fact that twigs are a favorite nest site for our eastern species. The branches
selected by apache are those through which wood-boring insects have driven passages. The ants carefully clean these passages of the detritus left by the insects which made them. In most cases the passages have a diameter several times as great as that of the ants, hence it would seem that the ants could be jarred out of the open ends of the passages without difficulty. This is not the case, for they cling to the walls with great tenacity. To get a11 the speci- mens out of a nest it is usually necessary to split the branch into small pieces so that all the passages are exposed. Ps. apache is not at all pugnacious. It will bite on occasion but it very rarely stings and the sting is not painful. Since many species of Pseudomyrmex, some much smaller than apache, sting severely on the slighest provocation, this be- havior is rather surprising.
The female of apache often becomes physogastric after the colony is well established. The intersegmental mem- branes do not bulge but are stretched tight between the separated gastric sclerites. Since the latter retain their curvature, the gaster of a physogastric female of apache looks like a white tube running through a series of close-



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Psyche
[December
fitting, golden rings. In this species brood is usually present during the entire year. In some nests this is also true of the sexual forms. Fully mature males and winged females have been taken from nests as early as March 20th and as late as November 3rd. In southern Arizona and northern Chihuahua most nests are free from sexual forms by the first of October. It seems clear, however? that the sexual forms occasionally remain in the nest over the winter. Four colonies containing mature males and females were taken in the Ajo Mountains of Arizona on March 20th and Zlst, 1952. Four days before snow had fallen in this area and the winter had been an unusually cool one. If the males and females in the above nests came from early