Last updated

Timema sp. - walking stick insect.jpg
Timema genevievae on the leaves of chamise (Adenostoma fasciculatum).
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Phasmatodea
Family: Timematidae
Genus: Timema
Scudder, 1895

21, and see text

Timema distribution map.jpg
Geographical distribution of Timema species in North America (Law & Crespi, 2002). T. morongense is found west of T. chumash but the extent of its full range is unknown. [1]

Timema is a genus of relatively short-bodied, stout and wingless stick insects native to the far western United States, and the sole extant member of the family Timematidae. The genus was first described in 1895 by Samuel Hubbard Scudder, based on observations of the species Timema californicum. [2] [3] [4]


Compared to other stick insects (order Phasmatodea), the genus Timema is considered basal; that is, the earliest "branch" to diverge from the phylogenetic tree that includes all Phasmatodea. To emphasize this outgroup status, all stick insects not included in Timema are sometimes described as "Euphasmatodea."

Five of the twenty-one species of Timema are parthenogenetic, including two species that have not engaged in sexual reproduction for one million years, the longest known asexual period for any insect. [5]


Timema poppense camouflaged on its host, Sequoia sempervirens (Redwood) Timema poppensis camouflaged on its host, Redwood (Sequoia sempervirens), California.jpeg
Timema poppense camouflaged on its host, Sequoia sempervirens (Redwood)

Timema spp. differ from other Phasmatodea in that their tarsi have three segments rather than five. For stick insects, they have relatively small, stout bodies, so that they look somewhat like earwigs (order Dermaptera). [6]

Cryptic coloration and camouflage

Timema walking sticks are night-feeders who spend daytime resting on the leaves or bark of the plants they feed on. Timema colors (primarily green, gray, or brown) and patterns (which may be stripes, scales, or dots) match their typical background, a form of crypsis. [7] [8]

In 2008, researchers studying the presence or absence of a dorsal stripe suggested that it has independently evolved several times in Timema species and is an adaptation for crypsis on needle-like leaves. All of the eight Timema species with a dorsal stripe have at least one host plant with needle-like foliage. Of the thirteen unstriped species, seven feed only on broadleaf plants. Four (T. ritense, T. podura, T. genevievae, and T. coffmani) rest during the day on the host plant's trunk rather than its leaves and have bodies that are brown, gray, or tan. Only two species (T. nakipa and T. boharti) have green unstriped morphs that feed on needle-like foliage; both are generalist feeders that also feed on broadleaf hosts. [7]

The species Timema cristinae exhibits both striped and unstriped populations depending on the host plant, a form of polymorphism that clearly illustrates the camouflage function of the stripe. [7] The earliest ancestors of this species were generalists that fed on plants belonging to both the genera Adenostoma and Ceanothus . They eventually diverged into two distinct ecotypes with a more specialist host plant preference. One ecotype prefers to feed on Adenostoma while the other ecotype prefers to feed on Ceanothus. The Adenostoma ecotype possesses a white dorsal stripe, an adaptation to blend in with the needle-like leaves of the plant, while the Ceanothus ecotype does not (Ceanothus spp. have broad leaves). The Adenostoma ecotype is also smaller, with a wider head, and shorter legs. [9]

These characteristics are genetically inherited and has been interpreted as the early stages of the speciation process. The two ecotypes will eventually become separate species once reproductive isolation is achieved. At the moment, both ecotypes are still capable of interbreeding and producing viable offspring, as such they are still considered a single species. [9] [10]

Life cycle and reproduction

Timema eggs are soft, ellipsoidal, and about two mm long, with a lid-like structure at one end (the operculum) through which the nymph will emerge. [11] Timema females use particles of dirt, which they have previously ingested, to coat their eggs. [12]

The eggs of many stick insects, including Timema, are attractive to ants, who carry them away to their burrows to feed on the egg's capitulum, while leaving the rest of the egg intact to hatch. [13] [14] The emerging nymph passes through six or seven instars before reaching adulthood. [14]

Timema males, in sexual species of Timema, show a consistent pattern of courting behavior. The male climbs onto the back of the female and, after a short display of vibrating and waving, they proceed to mate. (Rejection by the female is possible but uncommon.) The male then rides on the female's back for up to five days, a behavior often referred to as "guarding" the female. [15]

Several species of Timema are parthenogenetic: [16] that is, females can reproduce asexually, producing viable eggs without male participation.

According to Tanja Schwander, "Timema are indeed the oldest insects for which there is good evidence that they have been asexual for long periods of time." [5] She heads a team of researchers who found that five Timema species (T. douglasi, T. monikense, T. shepardi, T. tahoe and T. genevievae) have used only asexual reproduction for more than 500,000 years, with T. tahoe and T. genevievae reproducing asexually for over one million years. [5] [17]


Timema cf. californicum from the Santa Lucia Mountains of California. Timema californicum (Santa Lucia Range, California).jpg
Timema cf. californicum from the Santa Lucia Mountains of California.

The geographic range of Timema is limited to mountainous regions of western North America between 30° and 42° N. [16] They are found primarily in California, as well as in a few other neighboring states (Oregon, Nevada, Arizona) and in northern Mexico. [15] All are herbivores, primarily feeding on host plants found in chaparral. [16]

Host plants of the different Timema species include Pseudotsuga menziesii (Douglas fir), Sequoia sempervirens (Californian redwood), Arctostaphylos spp. (manzanita), Ceanothus spp., Adenostoma fasciculatum (chamise), Abies concolor (white fir), Quercus spp. (oak), Heteromeles arbutifolia (toyon), Cercocarpus spp. (mountain-mahogany), Eriogonum sp. (buckwheat), and Juniperus spp. (juniper). [1]


General phylogenetic relationships within Timema (Law & Crespi, 2002). Species marked with ♀ are parthenogenetic (female only). [1]

      Northern clade       

Timema poppense


Timema californicum


Timema douglasi  


Timema shepardi  


Timema knulli


Timema petita


Timema landelsense

      Santa Barbara clade       

Timema cristinae


Timema monikense  

      Southern clade       

Timema podura


Timema genevievae  


Timema bartmani


Timema tahoe  


Timema boharti


Timema chumash


Timema dorotheae


Timema ritense


Timema nakipa


Timema nevadense


Timema is the only extant member of the family Timematidae and the suborder Timematodea. Their clade is considered basal to the order Phasmatodea; [11] that is, many scientists believe that Timema-type stick insects represent the earliest "branch" to diverge from the phylogenetic tree that gave rise to all the stick insects of Phasmatodea. This primal distinction is referenced by the name "Euphasmatodea", which is given to all the clades of Phasmatodea other than the suborder Timematodea. [12] While formerly the only member of the family, in 2019 two fossil genera were described from the Cenomanian aged Burmese amber of Myanmar. [18]

Twenty-one species have been described; in addition there are at least two undescribed species known to exist: [7]

See also

Related Research Articles

<span class="mw-page-title-main">Asexual reproduction</span> Reproduction without a sexual process

Asexual reproduction is a type of reproduction that does not involve the fusion of gametes or change in the number of chromosomes. The offspring that arise by asexual reproduction from either unicellular or multicellular organisms inherit the full set of genes of their single parent and thus the newly created individual is genetically and physically similar to the parent or an exact clone of the parent. Asexual reproduction is the primary form of reproduction for single-celled organisms such as archaea and bacteria. Many eukaryotic organisms including plants, animals, and fungi can also reproduce asexually. In vertebrates, the most common form of asexual reproduction is parthenogenesis, which is typically used as an alternative to sexual reproduction in times when reproductive opportunities are limited. Komodo dragons and some monitor lizards can also reproduce asexually.

<span class="mw-page-title-main">Phasmatodea</span> Order of stick and leaf insects

The Phasmatodea are an order of insects whose members are variously known as stick insects, stick-bugs, walking sticks, stick animals, or bug sticks. They are also occasionally referred to as Devil's darning needles, although this name is shared by both dragonflies and crane flies. They can be generally referred to as phasmatodeans, phasmids, or ghost insects, with phasmids in the family Phylliidae called leaf insects, leaf-bugs, walking leaves, or bug leaves. The group's name is derived from the Ancient Greek φάσμα phasma, meaning an apparition or phantom, referring to their resemblance to vegetation while in fact being animals. Their natural camouflage makes them difficult for predators to detect; still, many species have one of several secondary lines of defense in the form of startle displays, spines or toxic secretions. Stick insects from the genera Phryganistria, Ctenomorpha, and Phobaeticus include the world's longest insects.

<span class="mw-page-title-main">Parthenogenesis</span> Asexual reproduction without fertilization

Parthenogenesis is a natural form of asexual reproduction in which growth and development of embryos occur in a gamete without combining with another gamete. In animals, parthenogenesis means development of an embryo from an unfertilized egg cell. In plants, parthenogenesis is a component process of apomixis. In algae, parthenogenesis can mean the development of an embryo from either an individual sperm or an individual egg.

<i>Carausius morosus</i> Species of insect

Carausius morosus is a species of Phasmatodea (phasmid) often kept as pets by schools and individuals. Culture stocks originate from a collection from Tamil Nadu, India. Like the majority of the Phasmatodea, C. morosus are nocturnal. Culture stocks are parthenogenetic females that can reproduce without mating. There are no reports of males, although in captivity, gynandromorphs are sometimes reared.

<span class="mw-page-title-main">Euphasmatodea</span> Suborder of insects

The Euphasmatodea, also known by its junior synonym Verophasmatodea is a suborder of the Phasmatodea, which contains the vast majority of the extant species of stick and leaf insects, excluding the Timematodea. The oldest record of Euphasmatodea is Araripephasma from the Crato Formation of Brazil, dating to the Aptian stage of the Early Cretaceous.

<i>Argosarchus</i> Genus of insect

Argosarchus is a monotypic genus in the family Phasmatidae containing the single species Argosarchus horridus, or the New Zealand bristly stick insect, a stick insect endemic to New Zealand. The name "horridus" means bristly in Latin, likely referring to its spiny thorax.

<i>Medauroidea extradentata</i> Species of insect

Medauroidea extradentata, commonly known as the Vietnamese or Annam walking stick, is a species of the family Phasmatidae. They originate in Vietnam and are found in tropical forests there. They eat a variety of foliage, though in captivity they commonly eat blackberry bramble, hawthorn, oak, red maple, and rose.

<i>Ctenomorpha marginipennis</i> Species of stick insect

Ctenomorpha marginipennis, the margin-winged stick insect, is a species of stick insect endemic to southern Australia. The species was first described by George Robert Gray in 1833.

<span class="mw-page-title-main">Black bean aphid</span> Species of true bug

The black bean aphid is a small black insect in the genus Aphis, with a broad, soft body, a member of the order Hemiptera. Other common names include blackfly, bean aphid, and beet leaf aphid. In the warmer months of the year, it is found in large numbers on the undersides of leaves and on the growing tips of host plants, including various agricultural crops and many wild and ornamental plants. Both winged and wingless forms exist, and at this time of year, they are all females. They suck sap from stems and leaves and cause distortion of the shoots, stunted plants, reduced yield, and spoiled crops. This aphid also acts as a vector for viruses that cause plant disease, and the honeydew it secretes may encourage the growth of sooty mould. It breeds profusely by live birth, but its numbers are kept in check, especially in the later part of the summer, by various predatory and parasitic insects. Ants feed on the honeydew it produces, and take active steps to remove predators. It is a widely distributed pest of agricultural crops and can be controlled by chemical or biological means. In the autumn, winged forms move to different host plants, where both males and females are produced. These mate and the females lay eggs which overwinter.

<i>Bacillus atticus atticus</i> Subspecies of insect

Bacillus atticus atticus is a species of phasmid or "walking stick" with recorded specimens in Greece, Italy, Croatia and Israel. In Cyprus, the endemic subspecies Bacillus atticus cyprius is present. Both can often be found climbing on plants

<i>Timema douglasi</i> Species of stick insect

Timema douglasi is a stick insect native to northern California and southern Oregon. It was first identified in 1996 as a specialist feeder on old-growth Douglas fir. It is one of five parthenogenetic species of Timema.

<i>Clitarchus hookeri</i> Species of insect

Clitarchus hookeri, is a stick insect of the family Phasmatidae, endemic to New Zealand. It is possibly New Zealand's most common stick insect. Clitarchus hookeri is often green in appearance, but can also be brown or red. Alongside the prickly stick insect and the Unarmed stick insect, C. hookeri is one of three stick insect species to have become naturalised in Great Britain, with all three having originated in New Zealand.

<i>Acanthoxyla</i> Genus of stick insects

Acanthoxyla is a genus of stick insects in the family Phasmatidae. All the individuals of the genus are female and reproduce asexually by parthenogenesis. However, a male Acanthoxyla inermis was recently discovered in the UK, probably the result of chromosome loss. The genus is the result of interspecific hybridisation resulting in some triploid lineages and some diploid lineages. The genus is endemic to New Zealand, but some species have been accidentally introduced elsewhere. The genus name Acanthoxyla translates from Greek as prickly stick.

<i>Acanthoxyla inermis</i> Species of stick insect

Acanthoxyla inermis is an insect that was described by John Salmon in 1955. Acanthoxyla inermis is included in the genus Acanthoxyla, and family Phasmatidae. No subspecies are listed. This species is native to New Zealand but has been unintentionally moved to Great Britain where it has grown a stable population and is the longest insect observed, and the most common of the stick insects that have established themselves on the island.

<i>Timema cristinae</i> Species of insect

Timema cristinae, or Cristina's Timema, is a species of walking stick in the family Timematidae. This species is named in recognition of the person who first found and collected it, Cristina Sandoval. It is found in North America, in a small region of southern California, US. T. cristinae is one of the smallest species of stick insects. They are flightless, and feed on the shrubs on which they live.

<i>Timema shepardi</i> Species of stick insect

Timema shepardi, Shepard's Timema, is a stick insect native to northern California. It was first identified in 1999. It is one of five parthenogenetic species of Timema.

Tanja Schwander is a Swiss evolutionary biologist and professor at the University of Lausanne. She is known for her work on the Evolution of sexual reproduction.

<i>Trachyaretaon</i> Genus of stick insects

Trachyaretaon is a genus of stick insects native to the Philippines.

<i>Orestes mouhotii</i> Species of stick insect

Orestes mouhotii is an insect species belonging to the order of Phasmatodea. Because of its synyonym Orestes verruculatus, it is the type species of the genus Orestes. Because of its compact body shape, the species is sometimes referred to as small cigar stick insect.

<i>Orestes guangxiensis</i> Species of stick insect

Orestes guangxiensis is a representative of the genus Orestes.


  1. 1 2 3 Jennifer H. Law & Bernard J. Crespi (2002). "The evolution of geographic parthenogenesis in Timema walking-sticks" (PDF). Molecular Ecology. Blackwell Science Ltd. 11 (8): 1471–1489. doi:10.1046/j.1365-294x.2002.01547.x. PMID   12144667. S2CID   45314005.
  2. Brock, P.D. "Species Timema californicum Scudder, 1895". Phasmida Species File Online. Retrieved 19 July 2011.
  3. Hebard, M. (1920). "The genus Timema Scudder, with the description of a new species, (Orthoptera, Phasmidae, Timeminae)" (PDF). Entomological News. 31: 126–132. Retrieved 19 July 2011.
  4. About Timemas | Timema Discovery Project
  5. 1 2 3 Davies, Ella. "Sticks insects survive one million years without sex". BBC. Retrieved 19 July 2011.
  6. Borror, Donald J.; Richard E. White (1998). A field guide to insects: America north of Mexico. Houghton Mifflin Harcourt. p. 86. ISBN   0-395-91170-2. Timema small, stout-bodied, earwig-like forms occurring in the far West
  7. 1 2 3 4 Sandoval, Cristina P.; Bernard J. Crespi (2008). "Adaptive evolution of cryptic coloration: the shape of host plants and dorsal stripes in Timema walking-sticks" (PDF). Biological Journal of the Linnean Society. 94: 1–5. doi: 10.1111/j.1095-8312.2007.00941.x . Retrieved 21 July 2011.
  8. Gullan, P.J.; P.S. Cranston (2010). The Insects: An Outline of Entomology. John Wiley and Sons. p. 367. ISBN   978-1-4443-3036-6. ... many stick insects look very much like sticks and may even move like a twig in the wind.
  9. 1 2 Lorraine Scanlon (2009). "Timema cristinae" (PDF). Eukaryon. 5: 87–90. Retrieved July 22, 2011.
  10. Patrik Nosil & Roman Yukilevich (2008). "Mechanisms of reinforcement in natural and simulated polymorphic populations". Biological Journal of the Linnean Society. 95 (2): 305–319. doi: 10.1111/j.1095-8312.2008.01048.x .
  11. 1 2 Jintsu, Yoshie; Toshiki Uchifune; Ryuchido Machira (2010). "Structural Features of Eggs of the Basal Phasmatodean Timema monikensis Vickery & Sandoval, 1998" (PDF). Arthropod Systematics & Phylogeny. 68 (1): 71–78. Retrieved 23 July 2011. The genus Timema Scudder, 1895 (Timematidae), endemic to western North America, is usually considered the basalmost clade of Phasmatodea, i.e., the sister group of the remaining Phasmatodea
  12. 1 2 Grimaldi, David (2005). Evolution of the Insects. Cambridge University Press. p. 213. ISBN   978-0-521-82149-0 . Retrieved 23 July 2011. ..the importance of this group is recognized today by its placement into a separate suborder, Timematodea, versus all other families (i.e. the Euphasmatodea)
  13. Hughes, L; M Westoby (1992). "Capitula on stick insect eggs and elaiosomes on seeds: convergent adaptations for burial by ants". Functional Ecology. 6 (6): 642–648. doi:10.2307/2389958. JSTOR   2389958.
  14. 1 2 "Phasmids" (PDF). Grzimek’s Animal Life Encyclopedia. Retrieved 24 July 2011.
  15. 1 2 Arbuthnott, D.; M G Elliot; M A McPeek; B J Crespi (2010). "Divergent patterns of diversification in courtship and genitalic characters of Timema walking-sticks" (PDF). Journal of Evolutionary Biology. 23 (7): 1399–1411. doi: 10.1111/j.1420-9101.2010.02000.x . PMID   20456561 . Retrieved 24 July 2011.
  16. 1 2 3 Crespi, B.J.; C.P. Sandoval (2000). "Phylogenetic evidence for the evolution of ecological specialization in Timema walking-sticks" (PDF). J. Evol. Biol. 13 (2): 249–262. doi: 10.1046/j.1420-9101.2000.00164.x . Retrieved 19 July 2011.
  17. Schwander, Tanja; Lee Henry; Bernard J Crespi (2011). "Molecular evidence for ancient asexuality in Timema stick insects" (PDF). Current Biology. 21 (13): 1129–34. doi:10.1016/j.cub.2011.05.026. hdl: 11370/8c189a5e-f36b-4199-934c-53347c0e2131 . PMID   21683598. S2CID   2053974.
  18. Chen, Sha; Deng, Shi‐Wo; Shih, Chungkun; Zhang, Wei‐Wei; Zhang, Peng; Ren, Dong; Zhu, Yi‐Ning; Gao, Tai‐Ping (October 2019). "The earliest Timematids in Burmese amber reveal diverse tarsal pads of stick insects in the mid‐Cretaceous". Insect Science. 26 (5): 945–957. doi: 10.1111/1744-7917.12601 . ISSN   1672-9609. PMID   29700985. S2CID   13787599.