DRAFT KEY TO IDENTIFY TIMEMA (Version 4-2026)

NOTE: This is a very preliminary draft of the key, but even so, it is based on essentially every known preserved specimen, plus many photographs on iNaturalist and BugGuide. It is not intended to provide IDs for 100% of all specimens, but instead to give positive IDs when they are possible, and pointing out situations where a positive ID cannot be given. This is an extremely important distinction for those of you posting images to iNaturalist, or looking at images there. There are at least as many undescribed species of Timema as there are described species, and you cannot enter a species name in iNaturalist for undescribed taxa. Any iNaturalist image for which a positive ID is not possible, or which is an undescribed species (of which there are at least 20!), should be identified ONLY TO GENUS.

NOTE: Because they are flightless, Timema do not disperse readily, and for many species, their geographic distribution is extremely limited, and the most reliable way to ID them is by knowing exactly where they were found. That is why the key relies heavily on geography rather than appearance. Read the text regarding geographic limits very carefully, and treat it as far more definitive than almost anything else. Some species are variable in appearance, with multiple color forms as nymphs, or even as adults. Most of the chaparral species feed on multiple host plants, while the conifer-feeders appear to all be limited to conifers (with one possible exception).

KEY:

(1) Where was the specimen seen/collected?

-- ARIZONA - go to (2)

-- CALIFORNIA - go to (3)

-- OREGON - only T. douglasi (conifers, females only); striped, dark greenish

-- MEXICO - go to (13)

-- NEVADA - So far, the only confirmed species in NV are (a) T. nevadense, which is probably a species complex, so far only known definitively from Clark County. It is grayish and mottled, with very indistinct striping. (b) T. tahoe, known from the area surrounding Lake Tahoe (southern Washoe County, Storey County, Carson City, and Douglas County). It is green with a pale midline stripe, and known only from females. (both on conifers)

-- ANY OTHER COUNTY IN NEVADA - never reported, and presumably undescribed. Please contact me to report any such records.

(2 - AZ) Which mountain (range) in Arizona? Arizona species are presently known for only the following areas, apparently only feeding on conifers, all above 1200 meters elevation, and all are mottled brownish to grayish in coloration:

-- MOUNT WRIGHTSON (Santa Rita Mountains, Pima County and Santa Cruz County) - T. ritense (known from only one specimen collected in the 1930s, never seen again since)

-- SANTA CATALINA AND RINCON MOUNTAINS (Pima County) - undescribed species, with description in preparation.

-- HUALAPAI MOUNTAINS (Mohave County) - T. dorotheae (T. coffmani appears to be a junior synonym, not a valid species)

-- HARCUVAR MOUNTAINS (Yavapai and LaPaz Counties) - another undescribed species, with description in preparation.

-- ANY OTHER MOUNTAIN RANGE IN ARIZONA - never reported, and presumably undescribed. Please contact me to report any such records.

(3 - CA) What part of California?

-- MOJAVE DESERT (defined as any part of San Bernardino County east of 116°30') - a few species, all undescribed, and apparently all associated with junipers or pinyon pines, and related to T. nevadense and the Arizona species group.

-- SIERRA NEVADA (eastern side of Central Valley) - remarkably, for such a vast area, there are only two species of Timema confirmed here: (a) T. tahoe, known only from the area around Lake Tahoe (mostly Placer, El Dorado, and Alpine counties; green with pale dorsal stripe) and (b) T. podura, known only from Kern County north to Mariposa County (mottled grayish). NOTE: only this Sierran population is true T. podura, described originally from Sequoia National Park. All of the other populations listed online and in the literature as T. podura, including from Mt. San Jacinto, are undescribed taxa, and their descriptions are being prepared as part of this study.

-- NORTHERN CALIFORNIA (defined here as all counties from Mendocino and Lake Counties northwards - three species known from females only: (a) T. douglasi - dark green, striped, feeding on conifers, ranges all the way up to Oregon and south but not reaching the Bay Area (b) T. shepardi - bright green with tiny yellow pustules, feeding on chaparral shrubs, mostly manzanita, ranging southwards but not reaching the Bay Area, and (c) northern "T. genevievae" - mottled gray, feeding on chamise, and known only from Lake County - strongly disjunct from the type locality of T. genevievae (in Santa Clara County), probably undescribed, awaiting detailed morphological analyses. NOTE: There are records in the literature identifying some specimens from Mendocino County as T. poppense, but these records are almost certainly misidentifications, as the population at the locality sampled contained no males, and was presumably T. douglasi.

-- SOUTHERN CALIFORNIA (defined here as all of Riverside County and San Diego County, all of San Bernardino county west of 116°30', and all of Los Angeles county east of 118°30'; NOTE: no Timema have ever been recorded from Orange County, and they are only recorded from the very southwestern corner of Imperial County, near the border with San Diego County) - go to (4)

-- ALL OF COASTAL CALIFORNIA (defined here as all the counties on the western side of the Central Valley, from Sonoma and Napa Counties southwards to the western edge of Los Angeles County [from 118°30' westwards], with no confirmed records from farther than 75 miles from the Pacific Ocean) - go to (7)

(4 - SoCal area) Is it bright green with lots of tiny yellow pustules? (a) Yes - then it's the T. chumash species group. The type locality of T. chumash is the San Gabriel Mountains, and anything matching that description, from that range, is positive to ID as T. chumash. There are also Southern California populations in the San Jacintos, the San Bernardinos, and the Santa Ana Mountains. All three populations are genetically different from one another and from the San Gabriel population, and therefore might be described as different species or subspecies. NOTE: it is very important that the yellow spots are genuinely pustule-like, where they are small visible bumps on the body surface and NOT just pigmented areas , as there are forms of other species that can be green with yellow spots but the body surface is smooth (b) No - go to (5)

(5) Is it fairly uniform green with a pale dorsal midline stripe? (a) Yes - then it's T. bartmani, and should be feeding on conifers. The type locality is the San Bernardino Mountains, so the population there should be considered a positive ID. There is also a population on Mt. San Jacinto that is an undescribed subspecies, and has a reddish tint to the head. T. bartmani is not known from anywhere else. (b) No - go to (6)

(6) Does the male intracercal process have a row of several small, fine teeth along the outer (right, and posterior) edge? (a) Yes - then it's in the T. podura species group, which is a mixture of multiple undescribed taxa, ranging widely across Southern California (even at low elevations, and sometimes feeding on plants like sage and buckwheat), and these are being described as part of the revision. True T. podura is only found in the Sierra Nevada. (b) No, there are only about 5 or so large teeth on the male intracercal process - then it's in the T. boharti species group. The type locality of T. boharti is Anza-Borrego, presently assumed to refer to the desert floor, within the State Park, so that population is the only population for which a positive ID can be provided. There are other populations in the Laguna Mountains to the west (possibly as far west as Palomar), and north of Anza-Borrego (mostly in the San Jacintos), and these appear to be a number of undescribed species, rather than true boharti. NOTE: members of the podura and boharti species groups are, collectively, very variable in coloration, especially as nymphs. The nymphs and females are effectively impossible to identify reliably, at this point in time. The green forms are difficult to distinguish from T. chumash unless you can tell for certain that the yellow spots are only pigment, and not pustule-like; the integument of these species is smooth, not covered with tiny bumps as in chumash. NOTE: Mount San Jacinto is presently the only location known where there are four species of Timema that occur together, though the bartmani population occurs at a higher altitude than the other three.

(7 - Coastal CA area) This is a large area, extending around 350 miles from north to south, and it contains a variety of different species. Some of them nicely sort out geographically, but not all of them. Some sort out by host plants, but not all of them. This portion of the key will focus on getting the more reliably recognized taxa IDed first, and move progressively to the more difficult ones.

-- SAN LUIS OBISPO COUNTY - there are only 2 species known from this county; both are undescribed, and occur nowhere else. One feeds on Sargent cypress, the other on Monterey pine. They are both medium to dark green, with some lighter striping or pale longitudinal dashes. Timema of any other appearance in this county are likely to belong to undescribed species in the podura species group.

-- SANTA MONICA MOUNTAINS - this mountain range runs along the coast from western Los Angeles County into eastern Ventura County (between 118°30'W and 119°). It contains only two confirmed species, and they are virtually identical; both are bright green with tiny yellow pustules, and both feed primarily on Ceanothus. One is sexual, however, and the other is not. The asexual species is T. monikense, endemic to this area. It is, at this point, not possible to positively identify T. monikense other than by DNA sequencing. The sexual species is the western segregate of the T. chumash species group, though it is probably not truly T. chumash. All males seen so far from this area have been of this species, and not T. monikense. Females and nymphs cannot be distinguished from monikense.

-- SANTA YNEZ MOUNTAINS (and slightly north of there) - this range runs along the coast from Santa Barbara County eastwards into western Ventura County (between 119° and 120°30'W, and between 34°25' and 35°N), and contains only one confirmed species, T. cristinae, which is endemic to this region. This species is extremely variable in appearance, and feeds on a variety of hosts, but no other taxa have been recorded in this area. It may be a very localized species complex of multiple taxa, and genetic analyses are ongoing.

-- SAN ANTONIO VALLEY (and eastwards throguh Del Puerto Canyon) - this area comprises the very southeastern edge of Alameda County, but is mostly in far eastern Santa Clara County and into western Stanislaus County. It contains only one species, T. genevievae, a mottled gray, asexual species that feeds on chamise and appears to be endemic to this location. No other Timema have been reported from this area, and a few males from Del Puerto Canyon are assumed presently to be exceptional males produced by a normally parthenogenetic lineage, rather than males from an overlapping population of a different sexual species. The disjunct population in Lake County is probably not true genevievae, nor is another disjunct population from Pinnacles National Monument.

-- ALL OTHER COASTAL AREAS (as defined above) - go to (8)

(8) Is it medium to dark green, smooth, with paler longitudinal striping, and (almost always) feeding on conifers (e.g., redwood or Douglas fir)? Yes - go to (9); No - go to (10)

(9) There are three or four taxa fitting this description that may occur here, but the transitional areas are not well-defined at this point, and it is even possible that there is only one striped conifer-feeding species in this area, and one chaparral feeder. The southern conifer-feeding species is T. knulli, known primarily from Monterey County (at least as far north as 36°22'N). It is unknown whether it occurs farther south. The intermediate species is T. poppense, and it occurs in Napa and Sonoma counties (the farthest north confirmed record is 38°31'N) and ranges south to Santa Cruz County (at least as far south as 37°N) and possibly farther. At this point it is uncertain where the southern limit of poppense is, or the northern limit of knulli, and it remains possible that poppense is only a synonym of T. knulli. The third possible species is T. douglasi, an asexual species presently known only from Mendocino County northwards; it is unknown where the southern limit of this species is, but it may be in Sonoma County, north of the range of poppense. As things stand, anything in this group north of 38°45' is considered to be douglasi (unless it is a male, in which case it must be poppense); anything between 37°00' and 38°45'N is considered to be poppense; anything south of 36°30' is considered to be knulli, except for T. petita, known from a single very small population along Highway 1 in southern Monterey County, and feeding on Ceanothus rather than conifers; other than size, however, it is not distinctly different from specimens identified as knulli collected on Ceanothus farther north, and may be only a subspecies of T. knulli.

(10) Is it bright green (rarely brownish), and covered with tiny yellow pustule-like bumps? Yes - go to (11); No - go to (12)

(11) Very much parallel to the preceding set of species, there are two or three taxa fitting this description that may occur here, but the transitional areas are somewhat more certain. None of these species are known to feed on conifers, preferring oaks, manzanita, and other chaparral plants. The southern species in this group is T. landelsense, known only from Monterey County, in the Big Creek Reserve. It has never been reported outside the Reserve, and it is quite possible that it is not a distinct species. What it may be instead is a southern population of T. californicum, which ranges from Mount Tamalpais and Mount Diablo south to Monterey County, nearly adjacent to the region where landelsense occurs (near the southern limit, individuals can be found that are slightly reddish or brownish (especially the legs) instead of green, but they still have the tiny yellow blisters). The third (or second) species is T. shepardi, an asexual species presently known only from Napa County northwards, and found almost exclusively on manzanita; it is unknown where the southern limit of this species is, but it is expected to be just north of the range of californicum. Females and nymphs cannot be distinguished from californicum except by DNA analysis, but any males that are bright green with yellow pustules from north of Monterey County are californicum.

(12) Other than the striped green species, and bright green species with yellow spots, there are virtually no other Timema reported from this sub-area (following couplet 8) with the exception of a few specimens in the T. podura species group (e.g., near Idria, Coalinga, Santa Clarita. and others), and these are mottled brownish to grayish, though none of these are likely to be actual T. podura, which is from the Sierra Nevada. At present, all podura-group species outside the Sierra Nevada except T. genevievae are undescribed, and only a few are well-known and easily defined.

(13 - Mexico) What part of Mexico?

-- CENTRAL BAJA (Sierra San Pedro Martir) - T. nakipa is the only species known from the region; it is fairly small and green with yellow pustules.

-- EXTREME NORTHERN BAJA (the border with San Diego County in the US) - there is an undescribed species related to T. podura that ranges from just east of Tecate (116°30') across to the edge of the desert (116°00'), and not reported from more than about 10 miles south of the US border. It is grayish to brownish. A description of this species is in preparation.

-- ANY OTHER PART OF MEXICO - never reported, and presumably undescribed. Please contact me to report any such records.