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

An instar ( /ˈɪnstɑːr/ ( Loudspeaker.svg listen ), from the Latin īnstar , "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).

Two instars of a caterpillar of Papilio polytes Common mormon (Papilio Polyetes) catapillars.jpg
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. Yet, 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 caterpillars will undergo. On the other hand, temperature affects 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] The number of larval instars in ants has been the subject of a number of recent investigations, [8] and no instance of temperature-related variation in numbers of instars has yet been recorded. [9]

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<i>Atta</i> (ant) Genus of ants

Atta is a genus of New World ants of the subfamily Myrmicinae. It contains at least 17 known species.

Fire ant Genus of red ants

Fire ants are several species of ants in the genus Solenopsis, which includes over 200 species. Solenopsis are stinging ants, and most of their common names reflect this, for example, ginger ants and tropical fire ants. Many of the names shared by this genus are often used interchangeably to refer to other species of ant, such as the term red ant, mostly because of their similar coloration despite not being in the genus Solenopsis. Both Myrmica rubra and Pogonomyrmex barbatus are common examples of non-Solenopsis ants being termed red ants.

Red imported fire ant Species of ant

The red imported fire ant, also known as the fire ant or RIFA, is a species of ant native to South America. A member of the genus Solenopsis in the subfamily Myrmicinae, it was described by Swiss entomologist Felix Santschi as a variant of S. saevissima in 1916. Its current specific name invicta was given to the ant in 1972 as a separate species. However, the variant and species were the same ant, and the name was preserved due to its wide use. Though South American in origin, the red imported fire ant has been accidentally introduced in Australia, New Zealand, several Asian and Caribbean countries, and the United States. The red imported fire ant is polymorphic, as workers appear in different shapes and sizes. The ant's colours are red and somewhat yellowish with a brown or black gaster, but males are completely black. Red imported fire ants are dominant in altered areas and live in a wide variety of habitats. They can be found in rain forests, disturbed areas, deserts, grasslands, alongside roads and buildings, and in electrical equipment. Colonies form large mounds constructed from soil with no visible entrances because foraging tunnels are built and workers emerge far away from the nest.

<i>Tapinoma melanocephalum</i> Species of ant

Tapinoma melanocephalum is a species of ant that goes by the common name ghost ant. They are recognised by their dark head and pale or translucent legs and gaster (abdomen). This colouring makes this tiny ant seem even smaller.

Emerald cockroach wasp Species of wasp

The emerald cockroach wasp or jewel wasp is a solitary wasp of the family Ampulicidae. It is known for its unusual reproductive behavior, which involves stinging a cockroach and using it as a host for its larvae. It thus belongs to the entomophagous parasites.

<i>Paratrechina</i> Genus of ants

Paratrechina is one of seven ant genera in the Prenolepis genus-group from the subfamily Formicinae. Six species are included in Paratrechina; one of which, the longhorn crazy ant, is a widespread, pantropical pest.

<i>Solenopsis molesta</i> Species of ant

Solenopsis molesta is the best known species of Solenopsisthief ants. They get their names from their habit of nesting close to other ant nests, from which they steal food. They are also called grease ants because they are attracted to grease. Nuptial flight in this species occur from late July through early fall.

Rasberry crazy ant Species of ant

The tawny crazy ant or Rasberry crazy ant, Nylanderia fulva, is an ant originating from South America. Like the longhorn crazy ant, this species is called "crazy ant" because of its quick, unpredictable movements. It is sometimes called the "Rasberry crazy ant" in Texas after the exterminator Tom Rasberry, who noticed that the ants were increasing in numbers in 2002. Scientists have reorganised the genera taxonomy within this clade of ants, and now it is identified as Nylanderia fulva.

<i>Solenopsis saevissima</i> Species of ant

Solenopsis saevissima, commonly known in Brazil as formiga de fogo, formiga-vermelha, or formiga-lava-pes, is one of more than 185 species in the genus Solenopsis. It, along with 13 other species, is also a member of the Solenopsis saevissima species group which are popularly known as fire ants.

Longhorn crazy ant Species of ant

The longhorn crazy ant, also known as "black crazy ant", is a species of small, dark-coloured insect in the family Formicidae. These ants are commonly called "crazy ants" because instead of following straight lines, they dash around erratically. They have a broad distribution, including much of the tropics and subtropics, and are also found in buildings in more temperate regions, making them one of the most widespread ant species in the world. This species, as well as all others in the ant subfamily Formicinae, cannot sting.

<i>Evania appendigaster</i> Species of wasp

Evania appendigaster, also known as the blue-eyed ensign wasp, is a species of wasp in the family Evaniidae. Its native range is not known, but it likely originated in Asia. Today it occurs throughout the tropics and subtropics and in many temperate regions. As with the rest of its family, the blue-eyed ensign wasp is a parasitoid known for specializing on cockroach eggs.

<i>Myrmelachista</i> Genus of ants

Myrmelachista is a Neotropical genus of ants in the subfamily Formicinae. The genus is found exclusively in the Neotropical realm. Little is known regarding their biology.

<i>Linepithema micans</i> Species of ant

Linepithema micans is a small species of ant from the genus Linepithema which was described by Forel in 1908. This ant is endemic to southern South America. In Brazil, it is considered a pest of vineyards in acting as the main species associated with the coccid Eurhizococcus brasiliensis. It is still a poorly studied species. Their abundant larvae are round and whitish, almost indistinguishable from the proximate species Linepithema humile, better known as the invasive Argentine ant.

Polybia paulista is a species of eusocial wasp occurring in Brazil, Paraguay, and Argentina.

<i>Trypoxylon</i> Genus of wasps

Trypoxylon is a genus of wasps in the family Crabronidae. All Trypoxylon species that have been studied so far are active hunters of spiders, which they paralyse with a venomous sting, to provide as food to their developing larvae. Depending on the species, they will either construct their own nest from mud or find cavities that already exist. These cavities can range from keyholes to nail holes to previously abandoned nests, and are generally sealed with mud to create cells for their larvae.

Trypoxylon lactitarse is a species of square-headed wasp in the family Crabronidae. It is found in Central America, North America, and South America. These are fairly common harmless black wasps that build muddy elongate nests on the external walls of houses and low-story apartments. Their characteristic nests resemble pan-flutes in shape, and are provisioned with spiders captured and paralysed by the mother wasp. It lays an egg within each elongate nest cell amongst the invalid spiders, from which a larva will hatch and slowly consume all spiders as food. This species apparently undergoes four larval moults until completing their development as pupae inside a black cocoon.

<i>Caenocholax fenyesi</i> Species of insect

Caenocholax fenyesi is a species of twisted-winged parasitic insects in the order Strepsiptera and family Myrmecolacidae. It has a sporadic distribution throughout North America, Central America, and South America. Chaenochlax brasiliensis is the only other named species in the genus.

Camponotus vittatus is a species of carpenter ant and one of the most common ants found around households in South America, particularly Brazil. It was originally described by Auguste Forel in 1904. The species is relatively large, caramel-coloured, omnivorous, and fast-moving. The species presents four larval stages which will spin a cocoon to pupate. The hairs of Camponotus larvae are quite abundant, and may present taxonomic importance. The larvae of both sexes are similar, with few diagnostic traits, such as the acquired shape towards pupation inside their cocoons.

Camponotus senex is a fairly common species of weaver ant from the New World. They are opportunistic cavity-dwellers, semi-nomadic carpenter ants which are found around grasslands in Central and South America. It is taxonomically believed to be a complex of cryptic species and was previously considered synonymous with Camponotus textor.which once included a distantly-related species of weaver-ant.

Camponotus textor, also known as Brazilian weaver ant, is a species of fairly common tree-dwelling ant native to South and Central America. It is believed to include a number of cryptic species, and previously were considered synonymous to the cavity-dwelling ant Camponotus senex, now thought to be only distantly-related.


  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)". 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.