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.
T. cristinae is among the smallest species of stick insects, with adults only reaching 2-3cm in length.They have rounded bodies, an elongated abdomen, and are wingless. This species also displays sexual dimorphism. The males are smaller (~2cm long) and thinner than females (~3cm long), and can also be distinguished by their red legs. Males and females also differ in their mandible shape and size, with female mandibles being much longer than those of their male counterparts.
T. cristinae has a great sense of smell.This is known because it was found that they have more olfactory proteins than other species of phasmids that have been studied.
T. cristinae is polymorphic in regard to both its body colour and pattern.At least four different morphs of T. cristinae have been described. The green morph (which has a green body with no pattern), the red morph (red body with no pattern), the grey morph (grey body with no pattern) and the striped morph, which has the same green body of the green morph, but also displays a white stripe down the length of its back. Although these morphs do differ in other characters, their most distinguishable differences are in their body colour and pattern (stripe or no stripe). There is also mention of a melanistic morph, which is dark brownish gray and unstriped, but it is unclear if this is a distinct morph or an alternate name for the gray morph. The green morph is pictured in the species box on the right side of this page.
This species is native to the Coast Range of southern California, US.It is exclusively found in a small region of mountainous habitat (~30km2) covered by chaparral - a specific type of shrubland plant community. It is the only species of Timema found in this area. The specific habitat of T. cristinae is within shrubs. In particular, it is most abundant on two species of shrub: Adenostoma fasciculatum (Rosaceae) and Ceanothus spinosus (Rhamnaceae). These two plant species differ greatly in appearance, especially with regard to their leaves. The first (A. fasciculatum) has small needle-like leaves, that grow in crowded bundles along its branches. The second (C. spinosus) has wide oval-shaped leaves which do not grow so clustered together. These differences are likely responsible for two of the different morphs of T. cristinae: the 'green' morph and the 'striped' morph (which is also green, but displays a white stripe down its back). Studies have shown that the green morph is best camouflaged on the leaves of C. spinosus shrubs, whereas the striped morph is best camouflaged on the leaves of A. fasciculatum shrubs. Lastly, the melanistic morph is camouflaged to the stems of both of these host-plants, but very obvious when on the leaves of either.
Females are able to reproduce throughout their lives, but lay just one egg at a time.When they lay their eggs, females ingest soil, which they then use to thoroughly coat the egg as it is laid. Interestingly, eggs which do not have access to soil will never hatch. Often eggs are simply dropped from the host-plants, although occasionally individuals will use their abdomens to insert them into the soil. Most eggs are laid in April and May, and go through a process of dormancy - termed diapause - where they delay development; this lasts for approximately 8 months until hatching begins in December. The eggs do not hatch all at once, but instead hatchings are scattered throughout December and January. Occasionally, some eggs will remain their dormant state for an additional year, waiting to hatch until the following December–January.
Mating in T. cristinae begins with the male climbing on top of the females abdomen.He then engages in courtship behaviours which involves leg and antenna waving, before attempting copulation. After males cease courtship, they remain motionless on the female's back. Matings in T. cristinae last several hours, after which time males will continue to ride on the females for hours or even days to prevent them from mating with other males. However this does not prevent females of T. cristinae from practicing polyandry, meaning females mate with multiple males.
The juveniles and adults of T. cristinae remain motionless on their plants during the day, choosing to feed and walk only at night.When their host-plant is disturbed (as in shaking the branches), individuals often drop to the ground. One of the ways they avoid predators is through death-feigning behaviour. During this behaviour, the individual remains completely immobile. Not all individuals are equally likely to feign death, this behaviour is most commonly seen in smaller individuals.
Populations of T. cristinae have been demonstrated to be able to survive wildfires.This might be due to the unique way that females coat their eggs, by ingesting soil.
Due to its morphs, T. cristinae is used as an eco-evolutionary model to study the ongoing process of evolution.Much of this research has focused on the green and striped morphs, as they provide camouflage for two different host-plant species: C. spinosus and A. fasciculatum respectively. Essentially, as predators such as birds are able to more easily identify individuals of a certain morph when they are on the 'wrong' host-plant - the one they are not ideally camouflaged for - those individuals are less likely to survive. Researchers predict that this means that these two morphs are at the beginning of the speciation event, or in other words the green and striped morphs will become two different species of stick insects, which are best adapted to one or the other host-plant species. This has generated a lot of research interest, as it allows researchers to study the process of evolution in real time, instead of working backwards to figure how and why a species evolved into multiple different species. This interest has even led to studies examining the genes which decide which morph an individual will display (what colour and pattern they will have).
Additionally, although T. cristinae exists in only a small region (~30 km2) there are some areas where only one of the two host-plant species is present, and other areas where the two host-plant species can be found right next to one another. These different types of areas allow researchers to study two different types of speciation. In areas with only one of the host-plant species, they are able to study allopatry, which is when the different groups (populations) are separated by a physical barrier, so they cannot reproduce with one another - in this case the areas with the other host-plant species are simply too far away. In areas where both host-plant species occur right next to each other, researchers can study parapatry - which is when groups (populations) of a species become two different species even though their habitats are only partially separated from one another. This means that members of the different groups are still able to reproduce with one another from time to time.
In evolutionary biology, mimicry is an evolved resemblance between an organism and another object, often an organism of another species. Mimicry may evolve between different species, or between individuals of the same species. Often, mimicry functions to protect a species from predators, making it an anti-predator adaptation. Mimicry evolves if a receiver perceives the similarity between a mimic and a model and as a result changes its behaviour in a way that provides a selective advantage to the mimic. The resemblances that evolve in mimicry can be visual, acoustic, chemical, tactile, or electric, or combinations of these sensory modalities. Mimicry may be to the advantage of both organisms that share a resemblance, in which case it is a form of mutualism; or mimicry can be to the detriment of one, making it parasitic or competitive. The evolutionary convergence between groups is driven by the selective action of a signal-receiver or dupe. Birds, for example, use sight to identify palatable insects and butterflies, whilst avoiding the noxious ones. Over time, palatable insects may evolve to resemble noxious ones, making them mimics and the noxious ones models. In the case of mutualism, sometimes both groups are referred to as "co-mimics". It is often thought that models must be more abundant than mimics, but this is not so. Mimicry may involve numerous species; many harmless species such as hoverflies are Batesian mimics of strongly defended species such as wasps, while many such well-defended species form Müllerian mimicry rings, all resembling each other. Mimicry between prey species and their predators often involves three or more species.
The Phasmatodea are an order of insects whose members are variously known as stick insects, stick-bugs, walkingsticks, 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.
Thrips are minute, slender insects with fringed wings and unique asymmetrical mouthparts. Entomologists have described approximately 7,700 species. They fly only weakly and their feathery wings are unsuitable for conventional flight; instead, thrips exploit an unusual mechanism, clap and fling, to create lift using an unsteady circulation pattern with transient vortices near the wings.
Polygonia c-album, the comma, is a food generalist (polyphagous) butterfly species belonging to the family Nymphalidae. The angular notches on the edges of the forewings are characteristic of the genus Polygonia, which is why species in the genus are commonly referred to as anglewing butterflies. Comma butterflies can be identified by their prominent orange and dark brown/black dorsal wings.
Enallagma cyathigerum is a species found mainly between latitudes 40°N and 72°N; It is widely distributed in the Palearctic, and the Nearctic species Enallagma annexum was at one time considered to be synonymous with it. The species can reach a length of 32 to 35 mm. It is common in many different countries including Russia, Sweden, Norway, Finland, the United States of America, and South Korea. Damselflies are an important link between the health of the aquatic ecosystem and its response to climate change.
Sexual mimicry occurs when one sex mimics the opposite sex in its behavior, appearance, or chemical signalling.
Gasteracantha fornicata is a species of spiny orb-weavers found in Queensland Australia. It is similar in shape to Austracantha minax which was originally described as Gasteracantha minax. It was described by Johan Christian Fabricius in 1775, the first Australian species of spider to be named and classified.
Ranitomeya imitator, is a species of poison dart frog found in the north-central region of eastern Peru. Its common names include mimic poison frog and poison arrow frog, and it is one of the best known dart frogs. It was discovered in the late 1980s by Rainer Schulte who later split it up into more subspecies; describing each as a specific color morph, and sometimes having a separate behavioral pattern. The acoustics, morphs, and behavior of the species have been extensively researched.
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.
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.
Eurycnema goliath, commonly known as the goliath stick insect, or the regal stick insect, is a large species of stick insect in the family Phasmatidae, endemic to Australia and considered one of the largest species of stick insects in the country. The species has the Phasmid Study Group number PSG14.
Arctia plantaginis, the wood tiger, is a moth of the family Erebidae. Several subspecies are found in the Holarctic ecozone south to Anatolia, Transcaucasus, northern Iran, Kazakhstan, Mongolia, China, Korea and Japan. One subspecies is endemic to North America.
Mantises are an order (Mantodea) of insects that contains over 2,400 species in about 460 genera in 33 families. The largest family is the Mantidae ("mantids"). Mantises are distributed worldwide in temperate and tropical habitats. They have triangular heads with bulging eyes supported on flexible necks. Their elongated bodies may or may not have wings, but all Mantodea have forelegs that are greatly enlarged and adapted for catching and gripping prey; their upright posture, while remaining stationary with forearms folded, has led to the common name praying mantis.
Chemical mimicry is a type of biological mimicry involving the use of chemicals to dupe an operator.
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.
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.
Enchenopa binotata is a complex of multiple species found mostly in Eastern North America, but have also been reported in Central America. They are commonly referred to as treehoppers and are sap-feeding insects. The species in the complex look similar to each other in morphology, but are identified as different species by the host plant they occupy.
Reinforcement is a process within speciation where natural selection increases the reproductive isolation between two populations of species by reducing the production of hybrids. Evidence for speciation by reinforcement has been gathered since the 1990s, and along with data from comparative studies and laboratory experiments, has overcome many of the objections to the theory. Differences in behavior or biology that inhibit formation of hybrid zygotes are termed prezygotic isolation. Reinforcement can be shown to be occurring by measuring the strength of prezygotic isolation in a sympatric population in comparison to an allopatric population of the same species. Comparative studies of this allow for determining large-scale patterns in nature across various taxa. Mating patterns in hybrid zones can also be used to detect reinforcement. Reproductive character displacement is seen as a result of reinforcement, so many of the cases in nature express this pattern in sympatry. Reinforcement's prevalence is unknown, but the patterns of reproductive character displacement are found across numerous taxa, and is considered to be a common occurrence in nature. Studies of reinforcement in nature often prove difficult, as alternative explanations for the detected patterns can be asserted. Nevertheless, empirical evidence exists for reinforcement occurring across various taxa and its role in precipitating speciation is conclusive.
Drosophila silvestris is a large species of fly in the family Drosophilidae that are primarily black with yellow spots. As a rare species of fruit fly endemic to Hawaii, the fly often experiences reproductive isolation. Despite barriers in nature, D. silvestris is able to breed with D. heteroneura to create hybrid flies in the laboratory.