Instar

An instar (/ˈɪnstɑːr/ (listen), from the Latin "form", "likeness") is a developmental stage of arthropods, such as insects, between each moult (ecdysis), until sexual maturity is reached.[1] Arthropods must shed the exoskeleton in order to grow or assume a new form. Differences between instars can often be seen in altered body proportions, colors, patterns, changes in the number of body segments or head width. After moulting, i.e. shedding their exoskeleton, the juvenile arthropods continue in their life cycle until they either pupate or moult again. The instar period of growth is fixed; however, in some insects, like the salvinia stem-borer moth, the number of instars depends on early larval nutrition.[2] Some arthropods can continue to moult after sexual maturity, but the stages between these subsequent moults are generally not called instars.

For most insect species, an instar is the developmental stage of the larval forms of holometabolous (complete metamorphism) or nymphal forms of hemimetabolous (incomplete metamorphism) insects, but an instar can be any developmental stage including pupa or imago (the adult, which does not moult in insects).

Common mormon (Papilio Polyetes) catapillars
Two instars of a caterpillar of Papilio polytes

The number of instars an insect undergoes often depends on the species and the environmental conditions, as described for a number of species of Lepidoptera. However it is believed that the number of instars can be physiologically constant per species in some insect orders, as for example Diptera and Hymenoptera. It should be minded that the number of larval instars is not directly related to speed of development. For instance, environmental conditions may dramatically affect the developmental rates of species and still have no impact on the number of larval instars. As examples, lower temperatures and lower humidity often slow the rate of development- an example is seen in the lepidopteran tobacco budworm[3] and that may have an effect on how many molts will caterpillars undergo. On the other hand, temperature is demonstrated to affect the development rates of a number of hymenopterans without affecting numbers of instars or larval morphology, as observed in the ensign wasp[4][5] and in the red imported fire ant.[6][7] In fact the number of larval instars in ants has been the subject of a number of recent investigations,[8] and no instances of temperature-related variation in numbers of instars have yet been recorded.[9]

Larva on a leaf2

Larva

Larva on a leaf3

Larva on a leaf

Movement of the larva of an unidentified butterfly

Larval development- Imperial moth
Imperial moth (Eacles imperialis) development from egg to pupa, showing all the different instars

References

  • The dictionary definition of instar at Wiktionary
  1. ^ Allaby, Michael: A Dictionary of Ecology, page 234. Oxford University Press, USA, 2006.
  2. ^ Knopf, K. W.; Habeck, D. H. (1 June 1976). "Life History and Biology of Samea multiplicalis". Environmental Entomology. 5 (3): 539–542. doi:10.1093/ee/5.3.539.
  3. ^ "tobacco budworm - Heliothis virescens (Fabricius)". entnemdept.ufl.edu. Retrieved 2017-11-09.
  4. ^ Fox, Eduardo Gonçalves Paterson; Solis, Daniel Russ; Rossi, Mônica Lanzoni; Eizemberg, Roberto; Taveira, Luiz Pilize; Bressan-Nascimento, Suzete (June 2012). "The preimaginal stages of the ensign wasp Evania appendigaster (Hymenoptera, Evaniidae), a cockroach egg predator". Invertebrate Biology. 131 (2): 133–143. doi:10.1111/j.1744-7410.2012.00261.x.
  5. ^ Bressan-Nascimento, S.; Fox, E.G.P.; Pilizi, L.G.T. (February 2010). "Effects of different temperatures on the life history of Evania appendigaster L. (Hymenoptera: Evaniidae), a solitary oothecal parasitoid of Periplaneta americana L. (Dictyoptera: Blattidae)". Biological Control. 52 (2): 104–109. doi:10.1016/j.biocontrol.2009.10.005.
  6. ^ Porter, Sanford D. (1988). "Impact of temperature on colony growth and developmental rates of the ant, Solenopsis invicta". Journal of Insect Physiology. 34 (12): 1127–1133. doi:10.1016/0022-1910(88)90215-6.
  7. ^ Fox, Eduardo Gonçalves Paterson; Solis, Daniel Russ; Rossi, Mônica Lanzoni; Delabie, Jacques Hubert Charles; de Souza, Rodrigo Fernando; Bueno, Odair Correa (2012). "Comparative Immature Morphology of Brazilian Fire Ants (Hymenoptera: Formicidae: Solenopsis)". Psyche: A Journal of Entomology. 2012: 1–10. doi:10.1155/2012/183284.
  8. ^ Fox, Eduardo G. P.; Smith, Adrian A.; Gibson, Joshua C.; Solis, Daniel R. [UNESP (1 October 2017). "Larvae of trap jaw ants, Odontomachus LATREILLE, 1804 (Hymenoptera: Formicidae): morphology and biological notes". Myrmecological News: 17–28. hdl:11449/163472.
  9. ^ Russ Solis, Daniel; Gonçalves Paterson Fox, Eduardo; Mayumi Kato, Luciane; Massuretti de jesus, Carlos; Teruyoshi Yabuki, Antonio; Eugênia de Carvalho Campos, Ana; Correa Bueno, Odair (March 2010). "Morphological Description of the Immatures of the Ant". Journal of Insect Science. 10 (15): 15. doi:10.1673/031.010.1501. PMC 3388976. PMID 20575746.
Aglia tau

Aglia tau, the tau emperor, is a moth of the family Saturniidae. It is found in Europe. The species was first described by Carl Linnaeus in his 1758 10th edition of Systema Naturae.

The wingspan is 60–84 mm. The moth flies in one generation from March to July depending on the location.

The larvae primarily feed on European beech, but also birch, Alnus glutinosa, Salix caprea. and Sorbus aucuparia. The larvae look rather like hickory horned devil caterpillars in the early instar

Crambus

The genus Crambus includes around 155 species of moths in the family Crambidae, distributed globally. The adult stages are called snout moths (a name shared with the rest of the family Crambidae), while the larvae of Crambus and the related genus Herpetogramma are the sod webworms, which can damage grasses.

Cryptochetidae

The Cryptochetidae are a small family of tiny flies (generally 2 to 4 mm long). Some twenty to thirty species are known. Generally they are metallic blue black, stoutly built, with the head broad and high and with clear wings. Like other species in the superfamily Lonchaeoidea, the Cryptochetidae have antennae with a cleft in the second segment. Unlike practically all Schizophora however, they lack an arista, or if they do have one, it is too small to distinguish with any confidence. The family name refers to this unusual distinction; "Cryptochetidae" literally means "those with hidden bristles". The adult flies also are unusual among insects in that they have only a single pair of abdominal spiracles — this is not a serious physiological challenge in such small insects.

Again in resemblance to other Lonchaeoidea, the Cryptochetidae do not have more than one proclinate orbital bristle on each side. The frons is densely setulose. The costa has a break at the end of the subcosta. The sixth abdominal sternite in the male is symmetrical and it has an 8th tergite. In the female the seventh tergite and sternite are fused, and the eighth segment is elongated.

The larvae are of biological and economic interest, being endoparasitoids of coccids. In Cryptochetum iceryae, which parasitizes Icerya, there are four larval instars. The first instar is sac-like and lacks both trophi and tracheae but at the caudal end it bears a pair of finger-like processes. The caudal end of the digestive tract is closed. During subsequent instars the caudal processes grow longer and become filamentous; in the final instar they are much longer than the whole body. These filaments probably are respiratory organs. Only a few species of Cryptochetidae have been described, and most of those occur in tropical countries. At one time they were allocated to the Agromyzidae but now are regarded as a separate family.

Danaus chrysippus

Danaus chrysippus, also known as the plain tiger or African queen, is a medium-sized butterfly widespread in Asia, Australia and Africa. It belongs to the Danainae subfamily of the brush-footed butterfly family Nymphalidae. Danainae primarily consume plants in the genus Asclepias, more commonly called milkweed. Milkweed contains toxic compounds, cardenolides, which are often consumed and stored by many butterflies. Because of their emetic properties, the plain tiger is unpalatable to most predators. As a result, the species' coloration is widely mimicked by other species of butterflies. The plain tiger inhabits a wide variety of habitats, although it is less likely to thrive in jungle-like conditions and is most often found in drier, wide-open areas.D. chrysippus encompasses three main subspecies: D. c. alcippus, D. c. chrysippus, and D. c. orientis. These subspecies are found concentrated in specific regions within the larger range of the entire species.The plain tiger is believed to be one of the first butterflies depicted in art. A 3500-year-old Egyptian fresco in Luxor features the oldest known illustration of this species.

Deroplatys

Deroplatys is a genus of mantis in the tribe Deroplatyini of the subfamily Deroplatyinae of the family Mantidae. They are native to Asia and several share the common name dead leaf mantis.

Eacles imperialis

Eacles imperialis, the imperial moth, is a Nearctic member of the family Saturniidae and subfamily Ceratocampinae. The species was first described by Dru Drury in 1773.

Integripalpia

The Integripalpia are a suborder of Trichoptera, the caddisflies. The name refers to the unringed nature of maxillary palp's terminal segment in the adults. Integripalpian larvae construct portable cases out of debris during the first larval instar, which are enlarged through subsequent instars. These cases are often very specific in construction at both the family and genus level.

La Liga Filipina

La Liga Filipina (lit. The Philippine League) was a progressive organization created by Dr. José Rizal in the Philippines in the house of Doroteo Ongjunco at Ilaya Street, Tondo, Manila in 1892.

The organization derived from La Solidaridad and the Propaganda movement. The purpose of La Liga Filipina is to build a new group sought to involve the people directly in the reform movement.

The league was to be a sort of mutual aid and self-help society dispensing scholarship funds and legal aid, loaning capital and setting up cooperatives, the league became a threat to Spanish authorities that they arrested Rizal on July 6, 1892 on Dapitan.

During the exile of Rizal, The organization became inactive, though through the efforts of Domingo Franco and Andres Bonifacio, it was reorganized. The organization decided to declare its support for La Solidaridad and the reforms it advocated, raise funds for the paper, and defray the expenses of deputies advocating reforms for the country before the Spanish Cortes. Eventually after some disarray in the leadership of the group, the Supreme Council of the League dissolved the society.

The Liga membership split into two groups when it is about to be revealed: the conservatives formed the Cuerpo de Compromisarios which pledged to continue supporting the La Solidaridad while the radicals led by Bonifacio devoted themselves to a new and secret society, the Katipunan.

Leaf miner

A leaf miner is any one of a large number of species of insects in which the larval stage lives in, and eats, the leaf tissue of plants. The vast majority of leaf-mining insects are moths (Lepidoptera), sawflies (Symphyta, close relatives of wasps), and flies (Diptera), though some beetles also exhibit this behavior.

Like woodboring beetles, leaf miners are protected from many predators and plant defenses by feeding within the tissues of the leaves, selectively eating only the layers that have the least amount of cellulose. When attacking Quercus robur (English oak), they also selectively feed on tissues containing lower levels of tannin, a deterrent chemical produced in great abundance by the tree.The pattern of the feeding tunnel and the layer of the leaf being mined is often diagnostic of the insect responsible, sometimes even to species level. The mine often contains frass, or droppings, and the pattern of frass deposition, mine shape, and host plant identity are useful to determine the species and instar of the leaf miner. A few mining insects feed in other parts of a plant, such as the surface of a fruit.

It has been suggested that some patterns of leaf variegation may be part of a defensive strategy employed by plants to deceive adult leaf miners into thinking that a leaf has already been preyed upon.

Luna moth

The Luna moth (Actias luna) is a Nearctic moth in the family Saturniidae, subfamily Saturniinae, a group commonly known as giant silk moths. It has lime-green colored wings and a white body. The larvae (caterpillars) are also green. Typically, it has a wingspan of roughly 114 mm (4.5 in), but can exceed 178 mm (7.0 in), making it one of the larger moths in North America. Across Canada, it has one generation per year, with the winged adults appearing in late May or early June, whereas farther south it will have two or even three generations per year, the first appearance as early as March in southern parts of the United States.As defense mechanisms, larvae emit clicks as a warning and also regurgitate intestinal contents, confirmed as having a deterrent effect on a variety of predators. The elongated tails of the hindwings are thought to confuse the echolocation detection used by predatory bats. A parasitic fly deliberately introduced to North America to be a biological control for the invasive species gypsy moth appears to have had a negative impact on Luna moths and other native moths.

Muscomorpha

The Brachyceran infraorder Muscomorpha is a large and diverse group of flies, containing the bulk of the Brachycera, and, most of the known flies. It includes a number of the most familiar flies, such as the housefly, the fruit fly, and the blow fly. The antennae are short, usually three-segmented, with a dorsal arista. Their bodies are often highly setose, and the pattern of setae is often taxonomically important.

The larvae of muscomorphs (in the sense the name is used here; see below) have reduced head capsules, and the pupae are formed inside the exoskeleton of the last larval instar; exit from this puparium is by a circular line of weakness, and this pupal type is called "cyclorrhaphous"; this feature gives this group of flies their traditional name, Cyclorrhapha.

Nomadinae

Nomadinae is a subfamily of bees in the family Apidae. They are known commonly as cuckoo bees.This subfamily is entirely kleptoparasitic. They occur worldwide, and use many different types of bees as hosts. As parasites, they lack a pollen-carrying scopa, and are often extraordinarily wasp-like in appearance. All known species share the behavioral trait of females entering host nests when the host is absent, and inserting their eggs into the wall of the host cell; the larval parasite emerges later, after the cell has been closed by the host female, and kills the host larva. The first-instar larvae of nomadines are specially adapted for this, and possess long mandibles they use to kill the host larva, though these mandibles are lost as soon as the larva molts to the second instar, at which point it simply feeds on the pollen/nectar provisions. Another unusual behavioral habit seen in adults of various genera is they frequently "sleep" while grasping onto plant stems or leaves with only their mandibles.

Ovoviviparity

Ovoviviparity, ovovivipary, ovivipary, or aplacental viviparity is a mode of reproduction in animals in which embryos that develop inside eggs remain in the mother's body until they are ready to hatch. This method of reproduction is similar to viviparity, but the embryos have no placental connection with the mother and generally receive their nourishment from a yolk sac. In some species, yolk sac supplies are supplemented, or largely replaced by, uterine secretions or other maternal provisioning. Examples include trophic eggs in the uterus, or even intrauterine cannibalism.

Extreme examples of intrauterine secretions occur in some species of insects; for instance, females of some Glossinidae, Hippoboscidae and other Hippoboscoidea retain one larva at a time in the uterus, where it feeds on intrauterine secretions analogous to "milk". When the young insect has completed its larval metamorphosis, the mother deposits it where it can dig in and pupate without further attention. She then proceeds to raise the next larva in the uterus.

The young of some ovoviviparous amphibians such as Limnonectes larvaepartus, are born as larvae, and undergo further metamorphosis outside the body of the mother. Members of genera Nectophrynoides and Eleutherodactylus bear froglets, not only the hatching, but all the most conspicuous metamorphosis, being completed inside the body of the mother before birth.

Among insects that depend on opportunistic exploitation of transient food sources, such as many Sarcophagidae and other carrion flies, and species such as many Calliphoridae, that rely on fresh dung, and parasitoids such as tachinid flies that depend on entering the host as soon as possible, the embryos commonly develop to the first larval instar inside the mother's reproductive tract, and they hatch just before being laid or almost immediately afterwards.

Paraneoptera

Paraneoptera is a monophyletic superorder of insects which includes four orders, the bark lice, true lice, thrips, and hemipterans, the true bugs. The mouthparts of the Paraneoptera reflect diverse feeding habits. Basal groups are microbial surface feeders, whereas more advanced groups feed on plant or animal fluids.

Passandridae

Passandridae, the "parasitic flat bark beetles," are a family of beetles notable for being one of the very few beetle families with larvae that are, as far as known, exclusively ectoparasitic on the immature stages of other beetles and Hymenoptera.Adults are small to moderate sized beetles, 3-35mm, with heavily sclerotized bodies that are either dorso-ventrally compressed (genera occurring under bark) or subcylindrical in cross section (genera inhabiting wood-borer tunnels). Adults are generally brown or black, rarely with a color pattern, with prominent mandibles, confluent gular sutures, thick, moniliform antennae, unequal tibial spurs on the front legs, and generally a characteristic system of grooves and/or carina on the dorsal surface.Larvae are highly modified for their parasitoid habits. First instar larvae are heavily sclerotized, flattened, and spiny. Later instar larvae are physogastric (swollen posteriorly), with simple setae, short unsegmented legs, and reduced mouthparts.Passandridae consists of 109 described species in nine genera. Only Passandra Dalman occurs in both the Old and New Worlds, being represented in the Neotropical region by a single species, P. fasciata (Gray). The genera Ancistria, Aulonosoma, Nicolebertia, and Passandrina are restricted to the Old World, while Catogenus, Passandrella, Scalidiopsis, and Taphroscelidia are found only in the New World. Only Catogenus and Taphroscelidia occur in the Nearctic. The largest genus is Ancistria, with 34 described species.

Platygastridae

The hymenopteran family Platygastridae (sometimes incorrectly spelled Platygasteridae) is a large group (over 1100 species) of exclusively parasitoid wasps, mostly very small (1–2 mm), black, and shining, with elbowed antennae that have an eight-segmented flagellum. The wings most often lack venation, though they may have slight fringes of setae.

The traditional subfamilies are the Platygastrinae and the Sceliotrachelinae. The former subfamily includes some 40 genera, all of which are koinobionts on cecidomyiid flies; the wasp oviposits in the host's egg or early instar larva, and the wasp larva completes development when the host reaches the prepupal or pupal stage. The latter subfamily is much smaller, including some 20 genera, and they typically have the rudiments of a vein in the forewings. They are generally idiobionts, attacking the eggs of either beetles or Hemiptera.

The former family Scelionidae is now considered to be another subfamily of Platygastridae, along with the subfamilies Teleasinae and Telenominae.

Polygonia c-album

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.

To reduce predation, both the larval and adult stages exhibit protective camouflage, mimicking bird droppings and fallen leaves, respectively. During the later stage of development, the larvae also develop strong spines along their backs. The species is commonly found in Europe, North Africa, and Asia, and contains several subspecies. Although the species is not migratory, the butterflies are strong fliers, resulting in an open population structure with high gene flow and increased genetic variation.

Small blue

The small blue (Cupido minimus) is a butterfly in the family Lycaenidae. Despite its common name, it is not particularly blue. The male has some bluish suffusion at the base of its upper wings but is mostly dark brown like the female. The species can live in colonies of up to several hundred and in its caterpillar stage is cannibalistic. The small blue is known for being the smallest butterfly found in the United Kingdom. It is a Priority Species for conservation in Northern Ireland and under the UK Biodiversity Action Plan.

Spicipalpia

The Spicipalpia are a suborder of Trichoptera, the caddisflies. The four families included in this suborder all have the character of pointed maxillary palps in the adults. The larvae of the different families have varying lifestyles, from free-living to case-making, but all construct cases in their final larval instar for pupation or at an earlier instar as a precocial pupation behavior. Although recognized under some phylogenies, molecular analysis has shown this group is likely not monophyletic.

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