KEYS TO THE SPECIES OF ANTS OF THE SAN GABRIEL MOUNTAINS IN SOUTHERN CALIFORNIAnts

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Des Lauriers, James, 2017. Ants of the san Gabriel Mountains in southern california: Keys to the
Species. pZTt-28,5.
lN: ECSZ Does lt: Revisiting the Eastern california shear Zone: 2017 Desert symposium Fietd Guide and
Proceedings. Calif. St. Univ. Desert Studies Consortium. 342 p.
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JAMBS DEs LAURIERs I errs or rHE sAN GABRTEL MoUNTAINS: KEYs ro rHE sPBcIEs
Ants of the San Gabriel Mountains in Southern
California: keys to the sPecies
f ames Des Lauriers
Dept. Biology, Chafey CoIIege, AIta Loma, CA 917i7, IIMDESL3g@gmaiI'com
Hy p op onera, L a siu s, Myrm eco cy stu s, My rmic a'
Neivamyrmex, Nylanderia, Pheidole' Pogonomyrmex'
Pseudomyrmex, Solenopsis, Stenamma and
Temnothorax. User-friendly keys to the genera can be
found in Fisher and Cover (2007) and Ward (2005)' You
should use one of these keys to identify your specimen
to genus. Then consulting the appropriate key in this
anthology will get you to species. If there is no key to
the genus you are interested in among the keys in
this anthology, it is because the genus contains only
one or two species recorded within the range and it can
be identified by visual comparison with the images of
California species at AntWeb.org. https:i/wwwantweb'
org/adml.do?name=California. Those species appear in
the alphabetical list of species that follows.
Aphaenogaster occidentalis, Brachymyrmex depilis,
Cardiocondyla mauritanica, Dorymyrmex bicolor and D'
insanus, Linepithema humile, Liometopum occidentale,
Manica bradleyi, Monomorium ergatogyna, Myrmica
punctinops and M. rugiventris, Polyergus vinosus,
P r e n ol e
p i s i mp ar i s, Str umigeny s c alifo rni c a, Ta p i no m a
sessile, Veromessor andrei andV. pergandei'
Unless otherwise indicated these keys are to workers
and include those species found in the San Gabriel
Mountains and immediate environs.
I identified ants by reference to Wheeler and Wheeler
(1986), Snelling (1973, 1976,1982), Snelling and George
(lg7g),Snelling et al., (2014) and AntWeb.org' The
website has automontage images of all of California's ant
species and is kept up to date. Identifications of most
species were checked by Andrew Suarez (then at UC'
Berkeley) or Philip Ward (UC, Davis). Matthew Prebus
(UC, Davis) checked the identification of some newly
described Temnothoraxand Gordon Snelling checked the
identifi cation s of N eiv amYrm ex.
These keys are a work in progress and I would
appreciate it ifyou direct my attention to errors or
ruggest.d improvements. Additional species will surely
be detected within the range. I would greatly appreciate
having those records pointed out to me so that they can
be added to the growing faunal list' I'd particularly like
to thank Mark Ikeda for his help in working through
some of the difficult couplets and for these many years
ofcollaboration. Students at Chaffey College helped by
using earlier versions of these keys and by pointing out
errors and ambiguities.
The east-west trending San Gabriel Mountains separate
the Los Angeles basin's Mediterranean climate on the
south from the Mojave Desert on the north. At 10,064 ft''
Mt San Antonio is the high point of the range' The range
lies between San Fernando Pass on the west and Cajon
Pass on the east, a distance of about 60 miles' The range
is about 20 miles wide and includes an area of about 980
mi2. On the south side, the base of the range is at about
2000 ft. and rises abrupt\ from the valley floor' The plant
communities there are dominated by scrub and chaparral
communities of various composition with oak and
mixed conifer communities extending to the high ridges'
Precipitation on these highest slopes ranges from 30-40
inches. On the north side, at elevations around 4000 ft''
junipers mark the base, then Pinyon/|uniper woodland
gives way to Conifer/Oak forests with White Fir forests
on the highest ridges. These communities receive 15-20
inches of precipitation, much of it in the form of winter
snow. Geologically, the range, along with the others of the
Transverse Ranges, is produced by the movement of the
Pacific Plate against the North American Plate along the
San Andreas Rift Zone. Schoenherr (1992) and Millar
(2012) offer overviews of the natural history and the
climatic and vegetation history of the region.
This complex, fire-dominated mosaic of plant
communities is an attractive place to study the rich ant
fauna. Ant surveys of Southern California include one
in San Diego County (Suarez et al', 1998) and another
of Santa Cruz Island (Wetterer et a1., 2000) but I have
been unable to find any study of the local region' Ward
(2005) reviewed the ants of California mostly at the
generic level. Ward's paper includes keys to the genera of
California ants.
With this literature in hand I set out to survey the
ants ofthe range beginning in 1999. Since then I have
recorded 97 species collected throughout the range' Des
Lauriers and Ikeda (under review) describe the results
of this survey and provide an annotated list, natural
history notes for each species and some biogeographical
inferences. The identification of these species has been
quite a challenge given the sparse literature and the
dynamic state of the taxonomy. To help my own efforts
and those ofmy collaborators I have produced a set
of sixteen keys. A key was made for each genus that
contains species that can't be confidently distinguished
by visual inspection of the automontage images found at
AntWeb.org.
This anthology ofkeys to the workers includes the
genera Camponotus, Crematogaster, Forelius, Formica'
278 2O17 DESERT SYMPOSIUM

Keys follow in alphabeticalorder
CAMPONOTUS
There are twenty two species in California eleven of which are
recorded in the San Gabriel Mountains. In constructing the
key extensive use was made of the following sources; Ward
(2005) and Wheeler & Wheeler (1986). The key is supported
by the images of California ants found at AntWeb.oig. Two
words of caution are warranted. In the San Gabriels C. tticinus
includes a black form as well as the typical bicolored form and
C. semitestaceus does not display the lobule at the base of the
scape that typifies the species elsewhere. Small individuals are
frequently unkeyable.
I Head, in profile, evenly arched from clypeal apex to vertex. ..2
Head, in profile, obliquely truncate below antennal
insertions. (stbg. Myrmaphaenus). ..........yogi
2(l) Clypeus without median notch, thickened; major workers
> 8 mm long. .............. ............ 3
Lower margin of median lobe of clypeus with narrow notch
in middle, thin, weakly convex and semicircularly depressed;
major worker < 8 mm long. (subg. Myrmentoma). ............... 4
3(2) Clypeus carinate to feebly so, iflatter then scape flattened at
base. (subg. Tanaemyrmex) ............................. g
Clypeus more or less ecarinate; scapes never flattened at the
base. (subg. Camponotus). ............................... 7
4(2) Mesosomal profile distinctly depressed at metanotal
suture. . .....hyatti
Mesosomal profile not depressed at metanotal
suture. .....,...... ..................,... 5
5(4) In profile view, crest ofpetiolar node narrowly
sharp.............. ...................... 6
In profile view, crest of petiolar node rounde d..... anthrax
6(5) In front vieq malar area with conspicuous short erect or
suberect hairs; propodeal profile angular..... .......... clarithorax
In front view, malar area without erect or suberect hairs
except a few at base of mandible; integument subpolished to
shiny. ............ ...................... essrgl
7(3) Dorsal surface of head and mesosomawith numerous erect
hairs; when viewed in profile, node ofpetiole rounded; body
surface with bluish metallic sheen. .............. ........... .Iaevigatus
Dorsal surface of head and mesosoma with no or few erect
hairs; when viewed in profile, node ofpetiole sharp; body
surface shinyblack. rquercicola
8(3) Base ofscape flattened, at least slightlybroader at base than
immediatelybeyond.. ........... 10
Scape narrowest at base, weakly flattened. ....................... 9
9(8) Integument hairy, pubescence on tergites 3 and 4 longer
than distancebetweenhairs. vicinus
Integument less hairy; length ofpubescenc€ on tergites 3 and
4 about equal to distance between hairs..... ........... maritimus\
(+ This species has not been collected in the San Gabriels but its
known range toward the west is close.)
l0(8) Margins of head of major, in frontal view, distinctly
convergent toward mandibular bases; scape with small lateral
2O17 DESERT SYMPOSIUM
JAMES DES LAURIERS I .I,NTS OT TTTE SAN GABRIEL MOUNTAINS: KEYS TO THE SPECIES
lobule at base; apex of scape of major exceeding vertex corner by
at least its apical breadth ...... . ll
Head of major quadrate, margins strongly convergent
immediately above mandibular base; scape base broad, flattened,
not lobulate; apex ofscape ofmajor exceeding vertex corner, if
at all, byless than its apical breadth sansabeanus
l1(10) Lobule at flattenedbase ofscape conspicuous in all sizes
of workers. dumetorum
Lobule at flattened base ofscape absent or only a suggestion
of it in the largest workers (this condition seems to be limited to
this region). ........ . semitestaceus
CREMATOGASTER
There are ten species of Crematogaster in California seven of
which have been recorded in the San Gabriel Mountains. C.
larreae and. C. opuntiae are desert species that might be found at
lower elevations on the north side ofthe range. This key to the
workers is modified from Wheeler and Wheeler (19g6) and from
the AntWiki site http://www.antwiki.org/wiki/Key_to_western_
US-Crematogaster. The characters are often ambiguous and
individuals with worn hairs add to the uncertainty. The photos
at AntWeb.org are very helpful.
1. Anteroventral tooth ofpetiole strikinglylarge; head
subquadrate; postpetiole trapezoidal in dorsal view, wider in
front, with straight; petiole much broader than in all the other
species. ... mutans
Without this combination of characters. ........................ 2
2. Pronotum sides densely, conspicuously punctate; thorax
without erect hairs or with a single erect hair on each pronotal
shoulder. (Hairs maybe worn. Check several specimens.) . . 3
Pronotum sides with some other type of sculpture or else 2 or
more hairs on each pronotal shoulder. .......... 6
3. Thorax and gastral tergites without erect hairs, may be worn.
Check several specimens. ................................. 4
An erect hair on each pronotal shoulder, may be worn.
Check several specimens. ................................. 5
4. Head and thorax reddish. ............... ............. depilis
............. Iarreae
Head and thorax black or dark brown.
5. Pubescence appressed on scape and head, hairs on l.tgastral
tergite about one hair length apart ............... opuntiae
Pubescence suberect on scape (look along the distal l/3) and
head, hairs on l"t gastral tergite closer than
one hair length apart. .............. ........................ . 9
6. Lower mesopleuron with distinct striae (very fine lines). . 7
Lower mesopleuron without striae, or a mere hint of one or
two................ .hespera
7. Scape not, or scarcely, surpassing occipital corner in
large specimens; mesonotal declivity smoothly curved or
inconspicuous; thorax weakly punctuate; occiput shiny. ...... .
marioni+
Scape surpassing occipital corner by I or 2 diameters;
mesonotal declivity abrupt and angular. . ...,..................... . 8
8. Head entirely striatopunctate; dull. ................ ....... coarctata
279

IAMES DEs LAURIERs I alrs or rnE sAN GABRTEL MoUNTAINS: KEYS ro rHE sPEcIEs
Head above eyes smooth and shining or with only weak
striae. ............., ........ mormonum
9. In dorsal view, postpetiole subquadrate and anterolateral
corners of petiole broadly rounded. '.'. mutans
In dorsal view, postpetiole narrower in front than in back
and anterolateral corners of petiole more acute...... califurnica
* Chaparral, arboreal, on manzanita, oak, riparian on oak.
ron4rus
1. A few standing hairs along the anterior margin ofthe scape
(viewed from above against a dark field) ........'.'...........mccooki
No standing hairs along the anterior margin of the
scape. .............. ........'... pruinosus
FORMICA
Formica is a large, complex Holarctic ant genus. Most of the
species are northern or are associated with wooded areas. There
are 43 species in California. I have modified the key of Wheeler
and Wheeler (1986) so that this key includes only the six species
so far known to occur in the San Gabriel Mountains. The key
is strongly supported by the images in Wheeler & Wheeler
(1986). This key is derived directly from Francoeur (1973). All of
the species in this key are in the fusca species group. On three
occasions while collecting along East Blue Ridge near Guffy
Camp I have seen an ant that is intherufa or sanguinea Group'
It might be F. aservabttl've never been quick enough to collect
it under the thorny Ceanothilr thickets. Keep a sharp eye out for
a surprise.
1. Eyes with short, erect hairs arising from between the facets; all
body surfaces covered with short, erect hairs..-.. Francoeuri 2
2. Strongly polymorphic; thorax opaque or subopaque; dorsal
gastric hairs long; surface strongly shining.'............ . subp olita
Feebly polymorphic or monomorphic; other characters
otherwise. .............'.........'......... 3
3. Concolorous black, blackish. .........................'..........argentea
Bicolored: head and thorax red, often infuscated with patches
ofreddish brown, especially on dorsum; gaster black or blackish
brown. ..............4
4. Epinotum high, its angle distinct. ..'.. gnala
Epinotum long and low, its angle reduced to an even
convexity. ..'.................""""""' 5
5. Scale of petiole low and, in profile, thick and broadly rounded
at summit, both faces convex but anterior moreso. . xerophila
Scale ofpetiole high and, in profile, thin and angulate at
summit' "" moki
HYPOPONERA
Perhaps all four of the species of Hypoponera that occur in
California also occur in the San Gabriel Mountains or the
immediate environs. I have records from the range for H.
CA-01 and H. opacior andfor H. punctatfssiza from nearby
Ontario. The keys that I've seen all seem to trace their ancestry
to Creighton (1950). I've made a key that works for the Southern
California material that I have at hand.
'':: *::::: : :: ::l ::: :T::: *:: liiiilii *,,,, -.
280
Mesopleuron partly to entirely granulate or punctate. ....2
2. Head and dorsal pronotum nearlybare ofpubescence, a few
appressed hairs may be present. ...................................... CA-01
Head and dorsal pronotum densely clothed with appressed to
decumbent pubescence. ................................... 3
3. Petiole in lateral view narrower dorsally than ventrally' the
anterior and posterior faces not parallel; Head and
body punctate over a smooth and shiny background. opacior
Petiole in lateral view not narrowed dorsally, the anterior and
posterior faces parallel; head and body
punctate-granulate, the background surface not particularly
shiny. .............. oPacicePs
Lesrus
Of the seventeen species of Lasius in California I have collected
only three in the San Gabriel Mountains. For high quality
images of all of these species see AntWeb.org. I think it likely
that more of the subterranean species will be discovered in the
range. Hand collecting and digging along the shallow roots of
shrubs maybe rewarded.
1. Color dark and eyes fully developed. ........................ alienus
Color pale to tan and eyes much reduced. ..-.-..-.-...-.......'. .2
2. Eye with fewer than about 20 facets; propodeum sparsely
hairy. ............. nr flavus
Eye with more than about 20 facets; propodeum abundantly
hairy. ............. .......... califurnicus
MYRMECOCYSTUS
There are 22 species of Myrmecocysfzs in California. Of those,
ten occur in the San Gabriel. Snelling (1976,1982) revised
the genus and produced keys to all three castes. Here I have
modified the worker key so that it contains only the 10 species
that have so far been recorded in the range. The images at
AntWeb.org are very helpful.
Key to the Subgenera: Workers
1. Integument either: (a) bicolorous, head and thorax
ferruginous, gaster black; (b) unicolorous, ferruginous or
orange; (c) unicolorous blackish or dark brown; mandibles six
or seven toothed; eye small, maximum diameter less than to
slightly exceeding length offirst flagellomere; ocelli present,
sometimes obscure in small individuals; diurnal, matinal or
crepuscular. ................'............ 2
Integument light yellow or brownish yellow; mandibles eight
to ten toothed; eye large, maximum diameter much exceeding
length offirst flagellomere; ocelli absent or much reduced;
nocturnal....... .. MyrmecocYstus
2. Small (HL not exceeding 1.26 mm), uniformlyblackish or
dark brown, usually with anterior one-third ofhead paler; erect
hairs very reduced on head and; pubescence sParse on head.
EremnocYstus
-- Larger (HL exceeding 0.83 mm), eitherbicolorous or
ferruginous; usually abundantly hairy, erect hairs numerous on
head and thorax, appressed pubescence usually dense on third
tergum; diurnal. '. Endiodioctes
Key to the species of Sub g. Myrmecocysfus: Workers
2O17 DESERT SYMPOSIUM

1. Large, highly polymorphic species, head length 1.0-2.0 mm
or more, usually in excess of 1.3 mm; metanotal suture usually
impressed and propodeum as long as high or longer, juncture of
dorsal and posterior faces
broadly rounded. ................... .......... . mexicanus
Smaller, moderately polymorphic species, head length 0.8-1.4
mm; metanotal suture not impressed; propodeum higher than
long, juncture ofdorsal and posterior faces abruptly rounded,
often subangulate. ................. testaceus
Key to the species of Subg. Eremnocystus: Workers
1. Antennal scape and dorsum ofpropodeum without fully erect
hairs. ............. creightoni
Antennal scape, usually, and dorsum ofpropodeum, always,
with some fully erect hairs. ..................... ............................ colei
Key to the species of Sub g. Enilioilioctes: Workers
1. Abundantly hairy species: 20+ erect hairs on malar area in
frontal view; scape, femora and tibiae with numerous suberect
to erect hairs on all surfaces; first three (usually four) terga with
dense pubescence; head width of major usually in excess of 1.7
mm. .............. semirufus
Less hairy species: fewer than 20 erect hairs on malar area
in frontal view, usually fewer than 6; scape and femora often
sparsely hairy ; third tergum often sparsely pubescent: head
width of major less than 1.7 mm. .....................2
2. Malar area, in frontal view, with six or more erect hairs evenly
distributed between eye and base of mandible....................... 3
Malar area, in frontal view, with not more than four erect
hairs, these confined to lower half, near base of mandible. . 4
3. Tergum IV conspicuously pubescent in specimens with
pronotal width in excess of 1.0 mm; erect hairs present on at
least halfofdistance between inner eye margin and antennal
socket; punctures offrontal lobes and frons ofvariable size and
irregularly distributed. semirufus
Tergum IV with pubescence, when present, verywidely
scattered: erect hairs present only adjacent to eye margin, not
extending more than 0.25 ofdistance between eye and antennal
socket; punctures of frontal lobes and frons uniformly minute,
evenly distributed. ................. ...............fIaviceps
4. Longest occipital hairs clearly longer than minimum eye
diameter in majors. ................. 5
Longest occipital hairs no more than 0.6 X minimum eye
diameter usually about 0.5. ......................... 6
5. Hairs on dorsal face ofhind femur appressed to subappressed;
frontal lobes and frons finely, closely and uniformly punctate;
mandible septemdentate: abdomen usually wholly orange-
ferruginous. wheeleri
Hairs on dorsal face ofhind femur suberect, conspicuous;
frontal lobes finely and very irregularly punctate with large
impunctate areas; mandible octodentate; abdomen usually black,
*:: :1 :::::: :: :T: :::: :::""""' !t)!"iil*,,,,
6. Tergum III with little or no pubescence. ............................ 7
Tergum III with dense pubescence. ...................... flaviceps
IAMEs DEs LAURTERS I nNrs or rHE sAN GABRTEL MouNTArNs: KEys ro rHE spEcIEs
7. Pubescence very sparse on face; head often subpolished and
shiny; side ofhead oflarge worker often converging; head,
thorax and legs brownish. mimicus
Pubescence abundant on face; head usually distinctly
tessellate, not notably shiny; side ofhead straight in frontal view;
head, thorax and legs ferruginous (top of head maybe slightly
brownish).
MYRMICA
kennedyi
There are eight species of Myrmica in California with two of
them in the San Gabriel Mountains. The key is supported by the
images of California ants found at AntWeb.org.
l. Lower mesopleuron conspicuously rugose; epinotal spine
much longer than the width of its apparent base... punctinops
Lower mesopleuron faintly or not rugose; Epinotal spine
about as long as the width of its apparent base. .... rugiventris
NEIUAMYRMEX
The ants in the genus Neivamyrmexwere revised by Snelling
and Snelling (2007) and Snelling & George (1979) surveyed the
army ants of the California deserts. There are nine species in
California. I have modified their keys so that this key includes
only the four species so far known to occur in the San Gabriel
Mountains. The key is supported by the images of California
ants found at AntWeb.org. and those in the original papers
which are available online.
The taxonomy ofthis genus appears to be in a state of
uncertainty. Most are very poorly known within our area.
Males are commonly attracted to lights. Workers are, as a
rule, collected in pitfall traps or at night when the foraging or
emigration columns maybe encountered. Bivouaced colonies are
rarely located. Some species, such as N. leonardi, are probably
wholly subterranean.
There are two pairs ofspecies that are ofparticular interest.
N. minor is known only from males and has been collected south
of Pearblossom . N. leonardi is known only from workers. These
two species may actually be a single species. Two other species
that occur in the immediate region, N. mojave (only males
known) and N. nyensis (only workers known) are also likely to be
a single species (Snelling & Snelling, 2007).
WORKERS
1. Node ofpetiole, from above, elongate, clearly longer than
broad; largest workers more than 5 mm lon g. .... . . 2
Node ofpetiole, from above, stout, about as broad as long;
largest workers 3-4 mm long; HW not exceeding 1.0 mm.
Ieonardi
2(1). Head more or less shiny, not densely sculptured and opaque;
at least side of pronotum usually distinctly shiny. ................ 3
Head and mesosoma opaque, densely and often coarsely
sculptured). ... nigrescens(part)
3(2). Basal margin of mandible evenly curved into masticatory
margin, without a tooth or corner at their
junction. .................................. . 4
Basal margin of mandible straight, forming distinct tooth or
angle with masticatorymargin. ............................................... 5
4(3). Dorsal surface ofpropodeum distinctly depressed below
*:l:l-:::::::::::::::::llt:_i,fi :,J,"8ffii.':l,
2O17 DESERT SYMPOSIUM 281

JAMEs DEs LAURTERs I ewrs or tnr sAN GABRTEL MouNTArNs: KEys ro rHE splctts
Dorsal surface ofpropodeum not distinctly depressed;
metafemur shorter, 5.2 x as long as deep. californicus
5(3). Mesosoma largely or entirely conspicuously roughened and
opaque or semiopaque; head relativelybroad. ..... opacithorax
Mesosoma smooth and shiny, with only occasional
indications of sculpturing on mesosoma; head relatively
narrow; a small species. nyensis
MALES
L Mandible sickle-shaped. ..................... minor
Mandible not sickle-shaped. ..................... 2
2(1). From above, dorsal surface ofhead forming distinct ridges
over antennal sockets; mesosomal dorsum
subopaque to opaque. nigrescens (typical form)
From above, dorsal surface ofhead rounded, not forming
distinct ridges over antennal sockets; Mesosomal
dorsum moderately shiny. ................. opacithorax
NYIAND.ERIA
The Californiaspecies ofants in the genus Nylanderiawere
revised by Kallal and LaPolla (2012). There are 5 species in
California one ofwhich is an undescribed species represented
by a single record. I have made the key so that it includes only
the three described species so far known to occur in, or near the
San Gabriel Mountains. The key is supported by the images of
California ants found at AntWeb.org and those in the original
paperwhich is available online at AntWeb.org.
1. Vertex ofthe head in frontal view concave; a desert species.
v;;;;#;; il;;;;;i il ;;;;il il;;; ;;;!1J," l i
2. Eye length /e head length or more; domestic habitats; color
dark brown. vividula
Eye length less than % head length; undisturbed natural
habitats; colorlightbrown. ................. magnella
Virtidula and magnellaworkers are often exceedingly difficult
to separate on morphological grounds. However the males are
easily separable. In frontal view the head length exceeds the
head width (measured just above the eyes) in N. vividula.lnN
magnella those dimensions are about equal. Also consult the
original paper, p. 4l for genital structure differences.
PHEIDOLE
The California species of ants in the genus Pheidole appear not
to have been specifically studied in a single publication. There
are 27 species in California. Snelling and George (1979) surveyed
the desert ants ofCalifornia and have keys for each ofthe castes.
I have modified their key so that it includes the 8 species so far
known to occur in the San Gabriel Mountains. Take note of the
fact that images of both major and minor workers are presented
for each species.
The key to the species groups is adapted from Wilson (2003).
The workers of Pheidole are dimorphic with the majors having
exceedingly enlarged heads as well as more robust bodies.
Minor workers far outnumber majors and the keys nearly always
require that you have specimens of both forms. Thus, collecting
methods must be able to confidently associate majors and
minors as members of one species. Sampling directly from nests
is the only sure way ofhaving that confidence.
Key to the Species Groups
l. Along with the bidentate or toothless hypostoma of the
major, the major and minor have a roughly quadrate or short-
rectangular head shape; i.e., in full-face view the lateral margins
ofthe head are straight to weakly curved, and the head capsule
is as wide or almost as wide as it is long. Minor: eyes large
compared to head size, the ratio of Eye Length to Head Length is
0.14 to 0.40. ......... pilifera grotp
Either the major and minor have moderately to strongly
curving sides ofhead; or the ratio ofEye Length to Head Length
*'T ::::: :: :_ : :: :::: ::::: ::::::: i:::ffi #'"",il
Key to the Pilifera Group (modified from Snelling and George
re7e.)
Minor Workers
l. Head sharply narrowed behind eyes to form a short neck at
occipital margin; Head Length about 1.3-1.4 times
Head Width. ........... desertorum
Head weakly to moderately narrowed behind eyes, not
forming neck at occipital margin; Head Length about 1.2 times
Head Width. .................... hyatti
Major Workers
1. Apex of antennal scape surpassing occipital margin; mesial
pair ofgular teeth slender, spiniform. . desertorum
Apex of antennal scape not attaining occipital margin; when
gular teeth present, mesial pair usually triangtlar ........ hyatti
Key to the Fallax Group (modified from Snelling and George
1979.)
MinorWorkers
1. Dorsum of head and thorax (usually) largely smooth and
shiny; punctulate, when present, obscure and limited
in extent; mesonotum, in profile, often evenly curved or straight;
scape exceeding occipital margin, ifat all, by
one-fifth its length or less. ............ ................... 2
Head and thorax closely and sharply punctulate with shiny
areas along middle of head and promesonotum; mesonotum
angulate in profile; scape surpassing occipital margin by about
one-fourth its length. sciophila
2. Propodeum conspicuously punctulate, with short, but
distinct, spines or teeth; occipital margin usually distinctly
concave; postpetiole, in profile more or less distinctly nodose.
..................... 3
Propodeum weaklypunctulate or smooth and shiny,
without spines or teeth, at most angulate at juncture of basal
and posterior faces; occipital margin flat or weakly concave;
postpetiole not nodose in profile. .............. . nr barbata
(There are two taxa here. One is typical P. barbata while the
other is determined by P. Ward in 2005 to be nr barbata.To my
eye those specimens resemble a pale P. rugulosa.)
3. EL at least 1.5 x OMD, interocular distance no more than 3.0 x
Eye Length, usually much less. ................................................. 4
EL no more than 1.1 x OMD, interocular distance about 3.5 x
Eye Length. rugulosa
4. Promesonotal hairs slender, flexuous, longest about equal to
EL, clearly greater than MOD ........... gihescens
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i::::::::::ili:ill:iltl_:::::: ::::::::i ::'?'
5. Occipital lobes and promesonotal dorsum smooth and shiny;
- tibial hairs few and deiumbent to erect. ................................. 6
Occipital lobes and promesonotal dorsum dull due to
microsculpture and punctulae; tibial hairs abundant and
erect. .............. ........... cerebrosior
6. Entire mesopleura coarselypunctate. rugulosa
Mesopleura faintly, partially punctate. ............ califu rnic a
L. MajorWorkers
1. Mesial pair of gular teeth absent; tops of occipital lobes'
sculpture rugulose or distinctly transversely striate. ............ 2
Gular teeth various; tops of occipital lobes smooth and shiny,
or variously sculptured, but not striate. ......... 3
2. Tops ofoccipital lobes distinctly transversely striate; mesial
pair ofgular teeth absent. rugulosa
Tops of occipital lobes more or less coarsely rugulose. ......
californica
3. Gular teeth absent; longest genal hairs at least 0.35 mm; OMD
equal to, or less than EL. .................. nr barbata
. At least one pair of gular teeth; longest gular hairs no more
than 0.25 mm, usually less than 0.20; OMD usually greater than
_ EL. .................... .........................4
4. Dorsum of head mostly smooth and shiny with scattered
coarse, piligerous punctures; promesonotal dorsum similar
or with coarse transverse rugulae with moderately punctulate
interspaces; mesial pair of gular teeth absent. ....................... 5
Dorsum of head and promesonotum densely
granulopunctate; mesial pair of gular teeth present, spiniform.
........ sciophila
5. Propodeal spines acute and well developed; standing hairs on
frons sparse or absent. cerebrosior
Propodeal spines little more than angular denticles; standing
hairs on frons numerous. ...................... gilvescens
GLOSSARY
EL = Eye Length............. MOD = Minimum Ocular Diameter
OMD = Oculomandibular Distance
POGONOMYRMEX
The California desert species of ants in the gews Pogonomyrmex
were described by Johnson & Overson (2009) and by Snelling
& George (1979).Trager (1998) has keys to the entire genus.
so that this key includes only the four species so far known to
occur in the San Gabriel Mountains. The key is supported by the
images of California ants found at AntWeb.org. and those in the
. original papers which are available online. These ants are armed
with a ferocious sting. Beware!
l. Venter of petiole (where ventral process would be) with I or
more distinct setae. ................ rugosus
Venter of petiole without setae. ... ............ 2
2. Propodeal spines present ............................... 3
Propodeal spines absent. .......... californicus
JAMES DEs LAURIERs I eNrs or rur sAN GABRTEL MouNTAINs: KEys ro rHE spEcIEs
3. Cephalic interrugal spaces with beaded sculpture. montanus
Cephalic interrugal spaces not beaded. ............. subnitidus
PSEUDOMYRMEX
Pseudomyrmex apache is the only member of the genus so
far collected in the San Gabriel Mountains or the immediate
environs. I have collectedP. pallidus at Whitewaterwash west
of Palm Springs and so I made keys modified from Ward (1985)
that work for the California material that I have at hand.
WORKERS
1. Eyes short (REL = 0.39-0.44). Scape length subequal to EL (SI
= 0.9- 1.0). . apache
Eyes longer (REL = 0.45-0.54). Scape length shorter than EL
(sr = 0.68-0.86). . .................... ................ pailidus
QUEENS
l. Larger (HW = 0.85-1.03), HL = 1.28-1.46). Eyes relativelyshort
(REL2 = 0.52-0.58). ...... apache
Smaller (HW =0.66-0.92, HL = 0.82-1.15). Eyes longer (REL2
= 0.59-0.71). . pallidus
MALES
1. Head broader (CI > 0.80) and not densely punctate. Eyes
shorter, EL about half head width (REL2 = 0.50-0.57) .. apache
Head elongate (CI < 0.80) and upper half densely punctate.
Eyes relativelylonger, EL about three-forths head width head
width (REL2 = 0.71-0.83). . pallidus
GLOSSARY
CI=HWHL HW = Head width SI2 = SL/EL
EL = Eye length REL = EL/HL
HL= Head length REL2 = EL/HW
SL - Scape length
sol,xNoPsls
There are eleven species of Solenopsis in California three of
which have been collected in the San Gabriel Mountains. There
are an additional three that maybe found around the periphery
of the range. I have made this key so that it includes the six
species that occur in, or near, the San Gabriel Mountains. The
key derived from Mackay (2002) and Pacheco and Mackay
(2013).
S. amplychila and S. aurea are desert species that might be
encountered on the lower north slopes. S. invicta is the imported
and invasive fire ant. I have records of it from as nearby as
Rancho Cucamonga, Fontana and Ontario so this species might
be encountered along the suburban interface with undisturbed
habitats.
Solenopsis CA-01 is known from a single location only -
Hwy 39, in San Gabriel Canyon at an elevation of 2100 ft. It was
collected by Roy Snelling in 1963. I collected at that location for
18 months without recording the species.
1. Eye containing fewer than 15 facets. (ThiefAnts) 2
Eye containing more than 20 facets. (Fire Ants) 3
2. Eye contains only I or 2 facets poorly defined; head elongate,
head length about 1.4X the head width. ...CA-01
Eye contains several well defined facets; head less elongate,
head length about 1.3X the head width. ...molesta
3. Gaster color dark brown-black. ............................................ 4
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IAMES DEs LAURTERs I enrs or rHE sAN GABRIEL MouNTArNs: KEys ro rHE spEcIEs
Gaster color yellow-red. ............................. 5
4. Clypeus with median tooth; mandibles with 4 teeth; petiolar
process reduced to absent. .......... ....... invicta
Clypeus without a median tooth; mandibles with 3 teeth, in
some there is a fourth small, isolated proximal tooth; petiolar
process distinct. ............. xyloni
5. Majorworkers. ................... ........................... 6
Minor workers. ..................... ..-.................... 7
6. In majors, two clypeal teeth distinct. .......................... aurea
In majors, clypeal teeth reduced. amblychila
7. In minor workers pronotal standing hairs number 6-8.
... amblYchila
In minor workers pronotal standing hairs number about 10.
STENAMMA
The California species of ants in the genus Stenamma were
revised by Snelling et al (1973). There are twenty species in
California. I have modified his key so that it includes only
the three species so far known to occur in the San Gabriel
Mountains. S. heathi is also included although it has not been
collected in the range. It has been collected both north and south
ofthe range. The key is supported by the images ofCalifornia
ants found at AntWeb.org. and those in the original paper which
is available online.
1. Median lobe of clypeus prolonged beyond clypheal margin, in
frontal view apex truncate; eyes relatively large, OMD 1.0-1.8 x
EL. .................. ..............-... smithi
Median lobe of clypeus short, not exceeding clypeal margin,
'" T:::::-::::::::::::::::::T:::::1""""'':::'i
2. First tergite half or more densely and closely punctulate, with
scattered coarse piligerous punctures and with fine striae over
basal half, forming reticulae anteriorly; head and thorax evenly
rugoso-reticulate................... ................... heathi
First tergite usually smooth and shiny; if sculptured,
sculpture limited to basal third or less, consisting of fine
punctulae and/or fine divergentbasal striae; head and thorax
usually not regularly rugoso-reticulate. .................................. 3
3. First sternite conspicuously sculptured, at least at sides,
usually much of segment densely punctulate or basal third with
conspicuous striae, either coarse or fine; first tergite usually
conspicuously sculptured. .......... californicum
First sternite wholly smooth and shiny, without punctulation
or striae; first tergite largely smooth and shiny, but with usual
short, separated divergent striae at base. . diecki+
GLOSSARY
EL - Greatest diameter eye length.
OMD - Oculo-mandibular distance.
* S. diecki is part of a difficult species complex. S. diecki does not
occur in Southern California mainland. The local, undescribed
taxon is given the code name Stenamma mgbt0t, (in Litt., PS
Ward,2017).
TEMNOTHORAX
The California species of ants in the genus Temnothorax was
recently revised by Snelling, et al (2014). There are twenty-two
species in California. I have modified their key so that it includes
only the eleven species so far known to occur in the San Gabriel
Mountains. T. pseudandrei is also included with the hope that
it will be discovered on the cottonwoods along the north side of
the range. The key is supported by the images ofCalifornia ants
found at AntWeb.org. and those in the original paper.
1. Antenna 1l-segmented. ............................... 2
Antenna l2-segmented. ............................. 4
2(1). Propodeal spines longer than 0.5 x distance between their
bases, PSI l9-30; pronotal dorsumcoarsely areolate-rugose or at
Ieast irregularly rugose. ................................... 3
Propodeal spines dentiform, always much less than 0.5 x
distance between their bases, PSI 6 -10; pronotal dorsum dull
and reticulate, without coarse areolae or rugae. ...... whitfordi
3(2). Petiole node profile subacute dorsally, with dorsal face
rounding evenly into posterior face of node; petiole 0.97-1.04
times longer than high in profile when length is measured on
a plane parallel to the venter ofthe petiole, from the anterior
flange of the peduncle to the posterior margin of the petiole
and the height is measured from the top of the node to the
ventral margin ofthe petiole in a plane orthogonal to the length
measurement; metafemur slender, 4.0- 4.7 times longer than
wide in dorsal view; ground-nesting, occasionally arboreal.
..'.' rugatulus
Petiole node broadly rectangular, with an oblique angle
between the dorsal and posterior faces of node; petiole 1.04-1.18
times longer than high in profile; metafemur stout, 3.5 -4.2 times
longer than wide in dorsal view; exclusively arboreal nesting
species............. caguatan
4(1). First gastral tergum moderately to slightly shiny, most of
disc distinctly finely sculptured. ........................................... . 10
First gastral tergum smooth and shiny, appearing polished,
devoid of sculpture other than scattered minute piligerous
punctures. ................................ 5
5(4). Petiole node triangular to subtriangular in profile. ..... 6
Petiole node rounded to rectangular in profile. (The trait is
subtle. Run both lugs of the couplet.) ............ 7
6(5). Propodeal spines as long as, or longer than, distance
between theirbases, PSI 20'26;arboreal species nesting in galls
and dead twigs. ...................... .................... gallae
Propodeal spines distinctly shorter than the distance
between their bases, PSI 10 -16; arboreal or ground nesting
species. .... nitens
7(5). Propodeal spines as long as, or slightly shorter than the
distance between their bases, PSI 15 -24; light to dark brown
ground nesting species. nevadensis
Propodeal spines distinctly shorter than the distance
between their bases, PSI 4-17; either arboreal or ground nesting;
color variable. .......................... 8
8(7). Postpetiole wide, PPW 1.47-1.98 x PTW ....................... 9
Postpetiole narrow, PPW 1.23-1.43 xPTW. .................... ll
284 2017 DESERT SYMPOSIUM

9(8). Postpetiole narrow relative to petiole, PPW 1.47 -1.76 x
PTW; mesosomal dorsum reticulate and variously
rugose in part, but not coarsely areolate with microreticulate
interspaces. ........ neomexicanus
Postpetiole wide relative to petiole, PPW 1.79-1.98 x PTW;
pronotal disc and dorsal face ofpropodeum coarsely areolate
with microreticulate interspaces. ..................................... wardi
10(4). Mesosomal dorsum with metanotal groove impressed,
pronotum distinctly higher than base ofpropodeum . .. paiute
Metanotal groove not impressed, mesosoma forms a smooth
convex profile ...... anaPhalantus
11(8). Cephalic venter with scattered fine setae; frons, in profile,
with short setae present along entire length, from base ofclypeus
to posterior margin. ............. .'.'.'...........-- andrei
Cephalic venter without setae; frons, in profile, with few
or no setae, but with 2 on lower vertex and 4 across Posterior
margin. .................. pseudandrei
(Look for T. pseudandrei on cottonwoods on the north side of
the range; arboreal.)
Glossary
CI - Cephalic Index: (HWHL) x (100).
FI - Femoral Length Index: (HFL/HW) x (100).
HFL - Hind Femoral Length: Maximum length of hind femur in
dorsal view, excluding trochanter.
0I - Ocular Index: (ELIHL) x (100).
PPW - Postpetiole Width: Maximum width of postpetiole in
dorsal view.
PSI - Propodeal Spine Index: (PSL/HL) x (100).
PI - Petiole index: (PPWPTW) x (100)
PSL - Propodeal Spine Length: the tip ofthe measured spine,
its base, and the center of the propodeal concavity between the
spines must all be in focus. Using a dual-axis micrometer, the
spine length is measured from the tip of the spine to a virtual
point at its base where the spine axis meets orthogonally with a
line leading to the median point ofthe concavity.
PTW - Petiole Width: Maximum width of petiole in dorsal view.
SI - Scape lndex: (SL/HL) x (100).
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