Where does grasshopper come from heat
- Where does grasshopper come from heat
- Where does grasshopper come from heat
- Keeping Insects
- Caring for a praying mantis, butterflies, stick insects and beetles
- Development and life cycle of grasshoppers
- Housing your grasshoppers
- Temperature and humidity
- Food and feeding grasshoppers
- Breeding grasshoppers
- Buying grasshoppers
- What triggers colour change? Effects of background colour and temperature on the development of an alpine grasshopper
- J. Pablo Valverde
- Holger Schielzeth
- Colour morph switches
- Temperature-cued colouration darkening
- Green-brown switches
- Colouration darkening
- Experimental setup
- Background colour treatment
- Temperature treatment
- Scoring of body colour
- Statistical analysis
- Availability of supporting data
Where does grasshopper come from heat
All grasshoppers begin their lives as eggs. Yet eggs represent the least known stage of the grasshopper life cycle. They are laid in the soil of the habitat and develop hidden from the view of humans. Eggs of a few species, however, have been studied in both field and laboratory (Fig. 9).
Figure 9. One intact and one broken egg pod, exposing the eggs of the migratory grasshopper, Melanoplus sanguinipes (Fabricius).
Incubation of eggs begins immediately after females deposit them in the soil. The embryo, at first a tiny disc of cells laying on the ventral side of the yolk surface and at the posterior end of the eggs (Fig. 10), grows rapidly, receiving nourishment from the nutrient stores in the yolk.
From left to right: Stage 1 (5%) Stage 3 (10%) Stage 7 (20%) Stage 10 (30%) Stage 12 (40%) Stage 19 (50%)
Figure 10. Selected stages in the development of a grasshopper embryo (Melaoplus sanguinipes) held at a constant temperature of 30 C. Left two figures show whole egg; other figures show embryos removed from egg. (Illustrations adapted from Riegert, 1961; stages idetified and designated for embryos of Aulocara elliotti by Saralee Visscher, 1966).
In seven days the embryo of the migratory grasshopper, Melanoplus sanguinipes , held at an incubation temperature of 30½C, reaches Stage 19. In this stage the embryos of many rangeland species such as Aulocara elliotti and Camnula pellucida cease growth and begin a diapause . The embryo of the migratory grasshopper, however, continues to develop and at Stage 20 actively moves from the ventral to the dorsal surface and revolves 180½ on its long axis (see Figure 10, Stage 20). After 15 days the embryo has grown to Stage 24, having achieved 80 percent of its development. It then ceases growth and enters diapause. The embryo of the twostriped grasshopper, and probably others also, enter diapause at this stage. Exposed to favorable incubation temperatures, the eggs of a few rangeland species, such as Arphia conspersa and Xanthippus corallipes , develop completely and hatch during the same summer they are laid. The immediate cause of cessation of embryonic growth (diapause) in eggs of the majority of rangeland grasshoppers appears to be the shutdown of growth hormones. The embryos remain physiologically active as transfer of nutrient materials from the yolk into the embryonic fat body and other tissues continues. Cold temperatures of winter, however, slow or end this process and embryos enter a dormant period.
For eggs laid in temperate regions to reach their maximum development before diapause, they must receive sufficient heat, usually measured as day-degrees of heat accumulated in the soil at egg depth. Eggs deposited late in the season or during a cold summer may not receive this amount of heat, especially in northern areas such as the Canadian provinces of Alberta, Manitoba, and Saskatchewan. Eggs that do not reach their potential stage of development have reduced hatchability the following spring and thus do not contribute as much to the maintenance of a population.
During winter, low ground temperatures eventually break egg diapause. As soon as the ground warms above threshold soil temperatures of 50 to 55½F in spring, the embryos are ready to continue their development. Research has shown that for the few species studied, eggs need 400 day-degrees by fall to attain maximum embryonic growth and another 150 day-degrees in spring to initiate hatching. For completion of embryonic growth from start to finish, eggs require totals of 500 to 600 day-degrees.
In spring the emergence of hatching grasshoppers may be readily observed. All embryos of a single pod usually wriggle out one after another within several minutes. Once out, they immediately shed an embryonic membrane called the serosa. An individual hatchling, lying on its side or back and squirming, takes only a few minutes to free itself (Fig. 11). During this time the hatchlings are susceptible to predation by ants. After the shedding of the membrane the young grasshoppers stand upright and are able to jump away and escape attacking predators. In spring, young grasshoppers have available green and nutritious host plants. The majority of individuals in grasslands are grass feeders, but individuals of some species are mixed feeders, eating both grasses and forbs. Others are strictly forb feeders.
Figure 11. The lifecycle of the bigheaded grasshopper, Alucara ellliotti (Thomas). During summer in bare spots of grassland the female deposits at intervals batches of eggs. As soon as the eggs are laid, they begin embryonic development and reach an advanced stage in which they enter diapause and pass the winter. In spring the eggs complete embryonic devlopment and hatch. The young grasshopper sheds a serosal skin, the exoskeleton hardens, and the nymph begins to feed and grow. After molting five times and developing through five instars in 30-40 days, it becomes an adult grasshopper with functional wings. The adult female matures groups of six to eight eggs at a time and deposits them in the soil at intervwls of three to four days for the duration of her short life.
As insects grow and develop, they molt at intervals, changing structures and their form. This process is called metamorphosis . A number of insects undergo gradual (simple) metamorphosis, such as grasshoppers. With this type of metamorphosis the insect that hatches looks like the adult except for its smaller size, lack of wings, fewer antennal segments, and rudimentary genitalia (Fig. 11). Other insects with gradual metamorphosis include the true bugs, aphids, leafhoppers, crickets, and cockroaches. The majority of insects undergo complete (complex) metamorphosis, as the eggs hatch into wormlike larvae adapted for feeding and have a vastly different appearance from that of the adult insect. Before full-grown larvae can become adult insects they must enter into the pupal stage. In this stage they develop and grow the adult structures. Common examples of insects that undergo complete metamorphosis are beetles, butterflies, bees, wasps, and flies.
For young grasshoppers to continue their growth and development and reach the adult stage, they must periodically molt or shed their outer skin (Fig. 11). Depending on species and sex, they molt four to six times during their nymphal or immature life. The insect between molts is referred to as an instar; a species with five molts thus has five instars. After shedding the serosal skin, the newly hatched nymph is the first instar. After each molt the instar increases by one so that the nymph consecutively becomes a second, third, fourth, and fifth instar. When the fifth instar molts, the grasshopper becomes an adult or an imago.
The new adult has fully functional wings but is not yet ready to reproduce. The female has a preoviposition period of one to two weeks during which she increases in weight and matures the first batch of eggs. Having mated with a male of her species, the female digs a small hole in the soil with her ovipositor and deposits the first group of eggs. Once egg laying begins, the female continues to deposit eggs regularly for the rest of her short life. Depending on the species, production may range from three pods per week to one pod every one to two weeks. The species that lay fewer eggs per pod oviposit more often than those that lay more eggs per pod.
The egg pods of grasshoppers vary not only in the number of eggs they contain but also in their size, shape, and structure. Based on structure, four types have been recognized. In type I a stout pod forms from frothy glue and soil surrounding the eggs; froth is lacking between the eggs. In type II a weaker pod is formed from frothy glue between and surrounding the eggs. In type III frothy glue is present between the eggs but does not completely surround them. In type IV only a small amount of froth is secreted on the last eggs of a clutch, and most of the eggs lie loosely in the soil. Grasshopper eggs themselves vary in size, color, and shell sculpturing. Depending on the species eggs range from 4 to 9 mm long and may be white, yellow, olive, tan, brownish red, or dark brown. Eggs of certain species are two-toned brown and tan.
Events in the life cycle of an individual species of grasshopper — hatching, nymphal development, and adulthood — occur over extended periods. The eggs may hatch over a period of three to four weeks. Nymphs may be present in the habitat eight to ten weeks and adults nine to 11 weeks. Because of the overlapping of stages and instars, raw field data obtained by sampling populations do not answer several important questions. For example, how many eggs hatched? How many individuals molted successfully to the next instar? What was the average duration of each instar? How many became adults? What was the average length of life and the average fecundity of adult females? To obtain answers to these questions, detailed sampling data must be treated mathematically.
Laboratory data may also be used in studying grasshopper life histories. Table 4 provides information on the life history of the migratory grasshopper, Melanoplus sanguinipes , reared at a constant temperature of 86½F and 30-35% relative humidity and fed a nutritious diet of dry feed, green wheat, and dandelion leaves. The entire nymphal period averages 25 days for males and 30 days for females. Each instar takes four to five days to complete development except for the last instar, which takes seven days. Adult longevity of males averages 51 days and females, 52 days. Longevity of adults in the field is no doubt briefer because of the natural predators and parasites cutting short the lives of their prey.
TABLE 4. Life history of the migratory grasshopper, Melanoplus sanguinipes, reared in the laboratory at a constant temperature of 86.5 F.
Where does grasshopper come from heat
Texas Cooperative Extension, Texas A&M University, College Station, Texas
Grasshoppers: Frequently Asked Questions, 2003
Dr. Allen Knutson,
Professor & Extension Entomologist, Texas Cooperative Extension
hy are grasshoppers so bad this year, again? Consecutive years of hot, dry summers and warm, dry autumns favor grasshopper survival and reproduction. Warm, dry fall weather allows grasshoppers more time to feed and lay eggs. The large numbers of grasshoppers present last fall left many eggs in the soil which hatched this spring. Also, rains in the spring when eggs are hatching drown young hoppers. Thus, dry weather in the spring favors their survival.
|Grasshopper, Brachystala magna|
Where do grasshoppers come from?
Grasshopper eggs are deposited in the soil l/2 – 2 inches deep in weedy areas, fencerows, ditches and hay fields. The eggs hatch in the spring and early summer. Eggs of different grasshopper species hatch out at different times, so young grasshoppers can be seen throughout the spring and early summer. Young grasshoppers, called nymphs, feed for about six weeks. Once nymphs reach the adult stage, they can fly. As weedy plants are consumed or dry in the summer heat, adult grasshoppers can fly from weedy areas and pastures to more succulent crops and landscapes.
When will grasshopper numbers decrease this season?
Although grasshoppers complete only one generation a year, eggs hatch over a long period of time. Development from egg to adult requires about 40-60 days. Also, eggs of different species hatch at different times so small grashoppers can be found throughout the growing season. Grasshopper can persist until late fall when old adults begin to die or when a killing frost occurs.
What can be done to reduce their numbers?
Weed control. Eliminating weeds will starve young hoppers and later discourage adults from laying eggs in the area. Destroying weeds infested with large numbers of grasshoppers can force the hungry grasshoppers to move to nearby crops or landscapes. Control the grasshoppers in the weedy area first with insecticides or be ready to protect nearby crops if they become infested. Grasshoppers deposit their eggs in undisturbed soil, as in fallow fields, road banks, and fence rows. Shallow tillage of the soil in late summer may be of some benefit in discouraging egg lay.
Are insecticides effective?
Grasshoppers are susceptible to many insecticides. However, insecticides typically do not persist more than a few days and grasshoppers may soon re-invade the treated area. The length of control will depend on the residual activity of the insecticides and the frequency of retreatment. Controlling grasshoppers over a large area will reduce the numbers present which can re-infest a treated area. Dimilin 2L provides long residual of young hoppers but is not effective against adults.
When should insecticides be applied?
Monitor grasshopper infestations and treat threatening infestations while grasshopper are still small and before they move into crops and landscapes. Immature grasshoppers (without wings) are more susceptible to insecticides than adults.
What about insecticide baits for grasshopper control?
Sevin 5 Bait is a ready-to-use bait which can be applied to many crop and non-crop sites, including around ornamentals and many fruit and vegetable crops. For those wanting to make their own grashopper bait, the labels for Sevin XLR and Sevin 4-Oil ULV provide directions for mixing these products with cereal grains to make a 2% to 10% carbaryl bait. The bait is labeled for use in rangeland, wasteland, ditch banks and roadsides. The label further states the bait is for use “only by government personnel or persons under their direct supervision (e.g. USDA, state and local extension personnel, etc.)”
Are biological control products such as Nolo Bait, Grashopper Attack, and others effective?
These products contain spores of a protozoan called Nosema locustae, formulated in a bait. Grasshoppers consuming the bait become infected by the Nosema organism. Some immature grasshoppers die while adults often survive but females lay fewer eggs. Nosema baits act too slowly and kill too few grasshoppers to be much value when the need for control is immediate.
Some insecticides for controlling grasshoppers in the home landscape at present (2003) include:
- Cyfluthrin. The active ingredient in Bayer Advanced Home and Garden Spray
- Bifenthrin. Active ingredient in Ortho Ready-to-Use Houseplant and Garden Insect Killer
- Permethrin. Active ingredient in Spectracide and other products.
- Acephate. Active ingredient in Orthene (at present, but being phased out).
Note: Tempo (cyfluthrin) and Demon (cypermethrin) are labeled for use by Professional Pest Control Operators (2003) for insect control in lawns and landscapes.
What insecticides can be used in ornamental production?
Several products may be used including those containing bifenthrin, lambda-cyhalothrin, diazinon, dimethoate, malathion, acephate and carbaryl (2003).
For more information, see: Extension bulletin L-5201, Grasshoppers and Their Control.
Caring for a praying mantis, butterflies, stick insects and beetles
Whether or not you want to keep grasshoppers as pets or as food insects for your reptile, mantis or other pet, this page is the place for you. Here you can find how to take care of grasshoppers and locusts, with a special focus on the “common” pet grasshopper species Locusta migratoria and Schistocerca gregaria. You will also learn how to breed them.
A grasshopper nymph. You can see it is not yet adult because of the short underdeveloped wings.
Grasshoppers fall in the order of Orthoptera, in the suborder Caelifera. Grasshoppers are sometimes called locusts. There are many species, the most famous ones are the desert grasshoppers that also occur in the bible as one of the plagues. Both species Locusta migratoria and Schistocerca gregaria are desert grasshoppers and are in the family Acrididae. Both species reach a size of around 7 cm in length.
Development and life cycle of grasshoppers
A female grasshopper lays eggs in small egg clusters, usually in the ground but she can also deposit them in plant material. Young grasshoppers are called nymphs and already look like miniature versions of the parents. Nymphs lack wings, only adult grasshoppers have fully functional wings. Grasshopper nymphs grow fast and shed their skin (molt) around 8 times in the process. At the last molt both males and females grow long wings that pass the abdomen.
It takes around 2 – 3 weeks for eggs to hatch. In around 4 weeks the nymphs reach adulthood. Around two weeks after that they begin to mate and produce eggs. If the temperature is low, development and breeding will slow down too. A grasshopper will die of old age when it has been an adult for around 5 months.
Schistocerca gregaria nymph
Housing your grasshoppers
Housing grasshoppers is easy. You need a container that is big enough, has some ventilation and can be closed properly to prevent escape. Grasshoppers can chew through fabric gauze, so net cages or cages with a fabric cover are not suitable for grasshoppers. A fauna box, a glass terrarium or a plastic terrarium with metal mesh for ventilation will do. If you keep the grasshoppers as pets, a glass terrarium with a mesh lid will look good. If you keep the grasshoppers to feed them to reptiles or praying mantises you a plastic container is more practical, as it is lightweight and cheaper. Make sure the container is big enough for all grasshoppers. Twelve adult grasshoppers need a cage of around 50 x 50 x 30 cm at least. Bigger is always better.
Fill the bottom of the container with dry sand, dry oatmeal flakes or dry coconut fibers. Place some dry twigs or branches in the enclosure to provide extra surface for the grasshoppers to sit on. The food of the grasshoppers, grass and/or leaves, will also serve as decoration and perching areas. Make sure light reaches into the container, either by a light bulb (see next section about Temperature) or by natural light. Direct sunlight shining into the enclosure could heat it up too much, make sure to prevent overheating.
Schistocerca gregaria nymph seen from top
Temperature and humidity
The grasshopper species Locusta migratoria and Schistocerca gregaria are desert species. They need a dry and warm environment to thrive. A too humid environment will result in infections and death of the grasshoppers. A too cold environment will slow down development and make breeding grasshoppers impossible.
Keep the temperature during the day between 25 and 35 degrees Celsius. By night you can allow the temperature to drop to 15 degrees Celsius. The best way to heat the enclosure of grasshoppers is with a regular light bulb. It is also possible to heat the terrarium with a species heat bulb, found in reptile-specialized pet shops. You can heat the enclosure with a heat mat too. More information about heating any insect enclosure can be read at our page Temperature.
Keep the humidity low by placing dry bedding in the enclosure (dry coconut fiber, oatmeal flakes or dry sand) and not spraying with water. Grasshoppers do need moisture to survive, but can get this from their food. Lightly spray fresh food with water before feeding it to your grasshoppers. If you feel like the enclosure is getting moist, for example when you have an enclosure with little ventilation or if the enclosure is placed in a room with high air humidity, then you can better skip the spraying of the food. The locusts will get all their moisture from the fresh plant material that you give them.
Locusta migratoria nymph
Food and feeding grasshoppers
Locusta migratoria and Schistocerca gregaria eat only plant material. The best food and easiest food you can give them is fresh grass. Even better is fresh reed, reedgrass or canary grass (Phalaris arundinacea) if available. Fresh wheat leaves, corn leaves and other vegetable plants may also be eaten. But actually, many plant species will be eaten by grasshoppers. You can try to feed them any kind of grass-like species; if they eat the plants, it means that this is a suitable plant species. Generally grasshoppers will refuse to eat any poisonous plants. Be very aware of insecticide, if any plant has been spraying with insecticide it will be deadly to your grasshoppers.
Place the food plants inside the enclosure of the grasshoppers. They will start to eat from it instantly. At some point the plant will be too dry to eat, then the grasshoppers should be fed again with fresh plants. Once in a while you should clear out all old dry plant material from the enclosure.
Schistocerca gregaria nymph
It is very easy to breed grasshoppers as long as you keep them in the right circumstances. They really need high temperature, low humidity and plenty of fresh food. If you have males and females, breeding will occur naturally. You don’t need to move the eggs or nymphs to a different container. If you like, you can of course. The nymphs are very small, so you might want to keep them in a different container than the parents to cater to their needs, prevent escaping and keep a better eye on them.
If you really keep grasshoppers well, you will be awarded with a lot of young grasshoppers. Make sure this is actually what you want! If you don’t want to breed with the grasshoppers, remove the bedding with the eggs or collect the eggs and place them in the freezer. This will kill the eggs before they start to develop. Never release grasshoppers into nature. They can cause plagues, disrupt nature and compete with native grasshopper species.
Locusta migratoria nymph
It’s actually very easy so buy grasshoppers. You can buy them in reptile-oriented pet shops. They are sold there as feeder animals. They are sold in different sizes, from small nymphs, to bigger nymphs and to adults. If you want to keep them for fun, you can better buy the nymphs. If you want to breed them, it’s faster to just buy the adults.
Make sure the grasshoppers look healthy when you buy them. There should not be any dead grasshoppers in the container.
Next page: Ants as pets
What triggers colour change? Effects of background colour and temperature on the development of an alpine grasshopper
J. Pablo Valverde
Department of Evolutionary Biology, Bielefeld University, Morgenbreede 45, 33615, Bielefeld, Germany
Department of Evolutionary Biology, Bielefeld University, Morgenbreede 45, 33615, Bielefeld, Germany
Colour polymorphisms are a fascinating facet of many natural populations of plants and animals, and the selective processes that maintain such variation are as relevant as the processes which promote their development. Orthoptera, the insect group that encompasses grasshoppers and bush crickets, includes a particularly large number of species that are colour polymorphic with a marked green-brown polymorphism being particularly widespread. Colour polymorphism has been associated with the need for crypsis and background matching and background-dependent homochromy has been described in a few species. However, when and how different environmental conditions influence variation in colour remains poorly understood. Here we test for effects of background colour and ambient temperature on the occurrence of colour morph switches (green to brown or brown to green) and developmental darkening in the alpine dwelling club-legged grasshopper Gomphocerus sibiricus.
We monitored individually housed nymphae across three of their four developmental stages and into the first week after final ecdysis. Our data show an absence of colour morph switches in G. sibiricus, without a single switch observed in our sample. Furthermore, we test for an effect of temperature on colouration by manipulating radiant heat, a limiting factor in alpine habitats. Radiant heat had a significant effect on developmental darkening: individuals under low radiant heat tended to darken, while individuals under high radiant heat tended to lighten within nymphal stages. Young imagoes darkened under either condition.
Our results indicate a plastic response to a variable temperature and indicate that melanin, a multipurpose pigment responsible for dark colouration and presumed to be costly, seems to be strategically allocated according to the current environmental conditions. Unlike other orthopterans, the species is apparently unable to switch colour morphs (green/brown) during development, suggesting that colour morphs are determined genetically (or very early during development) and that other processes have to contribute to crypsis and homochromy in this species.
Colour polymorphism has fascinated biologists since the time of Darwin, and its evolutionary meaning is still being revealed [1–3]. Colour polymorphism, defined here as within-species phenotypic variation, occurs throughout the animal kingdom in several taxa of birds, fish, mammals, frogs, molluscs, spiders, several insect orders and also in plants [4–9]. The occurrence of colour polymorphisms in natural populations can result from biased mutation, pleiotropy and trade-offs, gene flow, spatially and/or temporally fluctuating selection and negative frequency-dependent selection that can counter loss of variation by genetic drift [10–13]. Furthermore, developmental plasticity and phenotypic flexibility, if they do not invoke significant cost, might allow the maintenance of polymorphisms. This can be particularly advantageous in unpredictably variable environments.
Insects offer a multitude of examples for the coexistence of two or more colour morphs in groups such as grasshoppers, mantoids, cicadids, damselflies, lepidopterans and beetles [13–15]. There is ample evidence for genetic and environmental effects, as well as genotype-by-environment interactions in colour determination [14–18]. Several species appear capable of modifying their colour in response to various environmental cues such as temperature, predation threats, behaviour stimulus (e.g., crab spiders which try to blend with their background to ambush prey, ), among others . Within Orthoptera, colour polymorphism is present in dozens of species (reviewed in , see also [19, 20]). Two particularly eye-catching forms of colour polymorphism in orthopterans are a widespread green-brown polymorphism in grasshoppers and bush crickets and the famous phase polymorphism in locusts [14, 21]. Phase polymorphism is triggered by changes in population density which induces changes in colour (typically black patterns in gregarious versus pale green or brown colours in solitary phases) as part of more complex changes in morphology, physiology, behaviour and life history [22–26].
The green-brown polymorphism is far more widespread among orthopterans than phase polymorphism and does not correlate with obvious changes in morphology and/or behaviour. Many families and genera of orthopterans comprise species that display either green or brown morphs, while other species are polymorphic (e.g., in genera Decticus, Metrioptera, Oedaleus). In some species, one of the morphs is very rare (such as brown morphs in Decticus verrucivorus), while in others the ratios are far more even (as in Metrioptera roeselii) . With respect to environmental effects, green morphs seem to develop primarily under high humidity, while brown morphs are favoured under dry environmental conditions [15, 27, 28]. Besides the two very striking forms of colour polymorphism mentioned before, there is a range of more fine-scaled within-species variation in colour pattern and colouration among orthopterans [29, 30]. Groundhoppers, for example, differ substantially in their colour patterns, which can be categorized into variable numbers of discrete morphs [31, 32]. In other species, differences in colour are more continuous such as with colouration of species in the genus Oedipoda. Such fine-scaled variation seems to be partly under genetic, partly under environmental control [15, 16, 33]. Many species also show occasional pinkish, purple, yellow or blue colour morphs , further illustrating the diversity of colour in orthopterans.
A very interesting phenomenon associated with colour polymorphism is homochromy, which describes matching of body colouration with variation in the background pattern of the local habitat [14, 15, 20, 35]. Such matching might arise for four different reasons: (i) local adaptation due to multi-generational history of selection on genetic polymorphisms, (ii) selective mortality within generations, (iii) individual-level choice of matching habitat patches , and (iv) developmental plasticity of body colouration to match local conditions . Developmental switches are particularly intriguing, because they allow individual-level matching, which is likely advantageous if habitats are unpredictably variable across generations, but predictable from environmental cues over the lifetime of individuals. Developmental matching has been reported in orthopterans for species with fine-scale variation in colour pattern [37, 38], but also for species which present the green and brown colour polymorphism (Table 1 ).
Studies on the effects of background colouration on the occurrence of colour morph switches in green-brown polymorphic (upper section) and other polymorphic (lower section) orthopterans
|Proportion of Switches|
|Species||Background Material||matched||non-matched||matched||non-matched||Stages with Switches||Reference|
|a) Green-Brown Polymorphism|
|Acrida turrita||fresh/dry grass||62||145||4 %||86 %||after ecdysis|||
|Acrida turrita||painted sawdust||14||15||0 %||100 %||after ecdysis|||
|Acrida turrita||painted sawdust||32||0 %||imago|||
|Oedaleus decorus||NA||10||66||0 %||88 %||after ecdysis|||
|Schistocerca americana||coloured paper||74||0 %||across stages|||
|Schistocerca gregaria||coloured paper||58||312||0 %||63.5 %||within stages|||
|Locusta migratoria||coloured paper||58||237||69 %||24 %||across stages|||
|Rhammatocerus||habitat background||3000 >||90 % >||imago|||
|Chorthippus biggutulus||coloured paper||257||30 %||across stages|||
|b) Other Polymorphisms|
|Oedipoda sp.||earth, clay, coal, stone, chalk||12||92||0 %||80 %||after ecdysis|||
|Tetrix subulata||sand||312||16 %||across stages|||
|Tetrix ceperoi||sand||228||16 %||across stages|||
The proportion of switches was calculated for various studies based on multiple assays either on matched or non-matched background colour. Studies do not indicate precise time of colour morph switch occurrence, only final results of repeated colour assessments across nymphal stages are stated (in the case of Ergene all switches occur after an ecdysis event). Percentages reflect amount of indiv >
Orthopterans are preyed upon by a large diversity of species, including birds, lizards, amphibians, spiders and other insects and are frequently parasitized by parasitic flies and mites [24, 34]. Visually hunting predators might constitute a force that can favour homochromy and crypsis, since survival to the imago stage is critical to individual fitness. Predators might also impose frequency-dependent selection if they develop search images and preferentially prey upon the most common morphs . However, there are other influences that might affect body colour and this may or may not be in conflict with crypsis. For example, body colour is likely to affect the absorption of radiant heat and therefore play an important role in thermoregulation [13, 39–41]. It has repeatedly been reported that orthopterans raised under cool conditions are darker than those raised under warm conditions [16, 19, 42–44].
The club-legged grasshopper Gomphocerus sibiricus is a highly sexually dimorphic alpine dwelling grasshopper that exhibits the green-brown polymorphism present in many other orthopterans. Green individuals are rarer than brown morphs in most populations. Despite substantial fluctuations in population density [24, 45], the species does not show any typical phase polymorphism . It inhabits alpine pastures and grassland with a very heterogeneous composition of open terrain strewn with stones and mottled by various types of short grasses and herbaceous plants. Climate conditions in the mountains are very unpredictable and variable within and between years. The maintenance of the green-brown colour polymorphism could be aided by the heterogeneous habitat and/or temporal variability in climate conditions in the native habitat of G. sibiricus.
In the present study we aimed to test the effect of two known factors on developmental colour changes in G. sibiricus. First, we assessed the effect of background colour (green or brown) on colour morph development across almost the entire ontogeny. We were particularly interested in whether individuals are able to switch colour morphs to achieve homochromy as it has been described in other species (Table 1 ). We predicted that if individuals were able to switch colour morphs, then individuals whose colour morph mismatched the background colour would be capable of matching their background at an advanced developmental stage. Second, we assessed the effect of temperature by means of a radiant heat treatment on developmental darkness, while controlling for humidity, population density and food moisture content. Here we predicted that if individuals were capable of manipulate the degree of melanin in their cuticle, thermoregulation needs would promote a colouration darkening under conditions of low radiation. We followed individuals from the second nymphal stage through to the imaginal stage during two independent rounds of trials with two different radiant heat regimes. Individuals were exposed to experimental treatments from the second nymphal stage onwards. The long exposure to experimental conditions allowed us to evaluate if colour changes occur exclusively in connection with moults or if changes were possible even within nymphal stages.
A total of 78 indiv >2 = 5.05, df = 1, p = 0.025).
Colour morph switches
No colour morph switch was observed among the 34 individuals in cages with matched background colours (6 green individuals in green cages and 28 brown in brown cages in total for both rounds). Forty-four individuals (33 brown and 11 green) were exposed to unmatched backgrounds, but no colour morph switches were observed among these 44 individuals. Reasoning based on binomial sampling (see methods section) suggests that if G. sibiricus is capable of switch colour, the rate of colour morph switches is well below values reported in previous studies (c ≤ 0.07, Table 2 ). When we concentrate on the subset of the data where colour morph switches were most likely, given both non-matched background and temperature treatment (brown individuals on a green background under high radiant heat treatment), the probability of colour morph switch is still well below expectations (c ≤ 0.17, Table 2 ).
Number of individuals of G. sibiricus on mismatched backgrounds, all of which did not switch colour morph during development
|Morph & Background||Temperature|
|Green on Brown||n = 3||n = 0||n = 3|
|c ≤ 0.63||NA||c ≤ 0.63|
|Brown on Green||n = 9||n = 9||n = 18|
|c ≤ 0.28||c ≤ 0.28||c ≤ 0.15|
|Sum||n = 12||n = 9||n = 21|
|c ≤ 0.22||c ≤ 0.28||c ≤ 0.13|
|Morph & Background||Temperature|
|Green on Brown||n = 4||n = 4||n = 8|
|c ≤ 0.53||c ≤ 0.53||c ≤ 0.31|
|Brown on Green||n = 7||n = 8||n = 15|
|c ≤ 0.35||c ≤ 0.31||c ≤ 0.18|
|Sum||n = 11||n = 12||n = 23|
|c ≤ 0.24||c ≤ 0.22||c ≤ 0.12|
|Round 1 + 2|
|Morph & Background||Temperature|
|Green on Brown||n = 7||n = 4||n = 11|
|c ≤ 0.35||c ≤ 0.53||c ≤ 0.24|
|Brown on Green||n = 16||n = 17||n = 33|
|c ≤ 0.17||c ≤ 0.16||c ≤ 0.09|
|Sum||n = 23||n = 21||n = 44|
|c ≤ 0.012||c ≤ 0.13||c ≤ 0.07|
Table depicts number of indiv >
Temperature-cued colouration darkening
We observed a significant change in colouration darkness in both rounds of trials. Individuals in the second and third nymphal stages (N2 and N3) of the round 1, and in the N2 and N4 stages of the round 2 experienced a change in darkness which depended on the direction of the temperature treatment. Individuals in the low radiant heat treatment became darker in colour, while those in the high radiant heat treatment became lighter in colour (Table 3 , Fig. 1 ). Individuals in the N3 stage in the R2 did not show a significant change in colour, yet the sign of the point estimate is the same as in stages N2 and N4. Individuals in the N4 stage of the R1 and under a high radiant heat treatment got significantly darker with age. Most of the low radiant heat treatment individuals from the R1 had perished, with the single remaining individual becoming lighter. Unlike the situation in nymphal stages, individuals in the imago stage undergo a darkening in colour in both treatments within the first week after final ecdysis (Fig. 1 ).
Results of the random-slope mixed effects model used to test for effects of radiant heat treatment and larval age on colouration darkness in both green and brown coloured morphs
|N2 (n = 42)||N2 (n = 35)|
|N1||First nymphal stage|
|N2||Second nymphal stage|
|N3||Third nymphal stage|
|N4||Fourth nymphal stage|
The authors declare that they have no competing interests.
JPV and HS perceived and designed the experiment. JPV performed the experiments and drafted the manuscript. JPV and HS analysed the data and the manuscript. All authors read and approved the final manuscript.