: a stage in the life of an arthropod (such as an insect) between two successive molts
also : an individual in a specified instar
Examples of instar in a Sentence
Recent Examples on the Web
This period is called the third instar, and can last hours or days, according to the researchers. —
Saleen Martin, USA Today, 5 Dec. 2025 After running through its allotment of instars, a caterpillar ceases to be itself and becomes a pupa. —Elizabeth Kolbert, The New Yorker, 13 Mar. 2023 The fourth instar of the insect is bright red with black and white markings, Indiana DNR officials said. —Sarah Brookbank, The Enquirer, 27 July 2021 Each stage of molting is called an instar, and some insects molt up to five times before moving onto the next stage. —Liz Langley, National Geographic, 11 Aug. 2020 There are five instars (that is, stages of development resulting in skin shedding) of the nymphs. —Margaret Lauterbach, idahostatesman, 26 Apr. 2018
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Saleen Martin, USA Today, 5 Dec. 2025 After running through its allotment of instars, a caterpillar ceases to be itself and becomes a pupa. —Elizabeth Kolbert, The New Yorker, 13 Mar. 2023 The fourth instar of the insect is bright red with black and white markings, Indiana DNR officials said. —Sarah Brookbank, The Enquirer, 27 July 2021 Each stage of molting is called an instar, and some insects molt up to five times before moving onto the next stage. —Liz Langley, National Geographic, 11 Aug. 2020 There are five instars (that is, stages of development resulting in skin shedding) of the nymphs. —Margaret Lauterbach, idahostatesman, 26 Apr. 2018
Cite this Entry
“Instar.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.grautoblog.com/dictionary/instar. Accessed 25 Apr. 2026.
Copy CitationMedical Definition
instar
noun
in·star ˈin-ˌstär 
: a stage in the life of an arthropod (as an insect) between two successive molts
also : an individual in a specified instar
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