Dyar's Law (or "Dyar's Rule") is the observed standard that during development of the immature stages of an
arthropod, increases in highly
sclerotized body parts are predictable and regular by a relatively constant factor.
The law is named after
Harrison G. Dyar
Harrison Gray Dyar Jr. (February 14, 1866 – January 21, 1929) was an American entomologist. Dyar's Law, a pattern of geometric progression in the growth of insect parts, is named after him. He was also noted for eccentric pursuits which includ ...
who in 1890 published a paper about his observation that the head capsule widths of
lepidopteran larvae follow a
geometric progression in growth.
However, various authors have noted that an earlier publication in 1886 by W.K. Brooks independently described the same phenomenon in
crustaceans, and therefore the variant term Brooks-Dyar Law (or "Brooks Rule" or "Brooks-Dyar Rule") also commonly appears in the literature. The earliest known citation of either authors' observations constituting a "Law" dates to a 1925 reference to "Dyar's Law".
Though the progression can be influenced by
abiotic and
biotic
Biotics describe living or once living components of a community; for example organisms, such as animals and plants.
Biotic may refer to:
*Life, the condition of living organisms
*Biology, the study of life
* Biotic material, which is derived from ...
factors such as temperature and food,
Dyar's Law can be accurately used to differentiate
instars of immature insects and to predict the size of instars missing from samples, crucial data for accurately delineating insect developmental histories.
Initially based on observations of crustaceans and insect larvae, this Law has been applied to immature arthropods in general.
Some 80% of entomological studies published from 1980 to 2007 that examined the validity of Dyar's observations supported the Law.
References
{{reflist
Arthropod anatomy