Dyar's Law

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.[1] The law is named after Harrison G. Dyar who in 1890 published a paper about his observation that the head capsule widths of lepidopteran larvae follow a geometric progression in growth.[2] However, various authors have noted that an earlier publication in 1886 by W.K. Brooks independently described the same phenomenon in crustaceans,[3][4] and therefore the variant term Brooks-Dyar Law (or "Brooks Rule" or "Brooks-Dyar Rule") also commonly appears in the literature.[5][6] The earliest known citation of either authors' observations constituting a "Law" dates to a 1924 reference to "Dyar's Law".[7]

Though the progression can be influenced by abiotic and biotic factors such as temperature and food,[8] 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.[1] Some 80% of entomological studies published from 1980 to 2007 that examined the validity of Dyar's observations supported the Law.[1]

References

  1. 1 2 3 Vincent H. Resh and Ring T. Cardé (eds.). 2009. Encyclopedia of insects, Second Edition, Academic Press, Burlington, Mass., pp. 432–433; https://books.google.com/books?id=Jk0Hym1yF0cC&pg=PA432&lpg=PA432&dq=%22Dyar%27s+Law%22&source=bl&ots=Tw_Si1z3rO&sig=EdXhEGNK9GxBtatAyBANcFDyvN4&hl=en&sa=X&ei=YeEuT5y5MIetgwfE38HfDw&ved=0CFoQ6AEwCQ#v=onepage&q=%22Dyar%27s%20Law%22&f=false, accessed 5 Feb 2012.
  2. ↑ Harrison G. Dyar. 1890. The number of molts of lepidopterous larvae. Psyche 5:420–422.
  3. ↑ Brooks WK 1886. Report on the Stomatopoda collected by H.M.S. Challenger during the years 1873–76. In: The voyage of H.M.S. Challenger, report 45, vol.16
  4. ↑ Crosby, T.K. 1973 Dyar's rule predated by Brooks' rule. New Zealand Entomologist: 5 (2):175-176
  5. ↑ Daly, H.V. 1985 Insect morphometrics. Annual Review of Entomology 30: 415-438
  6. ↑ Floater, G.J. 1996 The Brooks-Dyar Rule and morphometrics of the processionary caterpillar Ochrogaster zunifer Herrich-Schaffer (Lepidoptera: Thaumetopoeidae). Australian Journal of Entomology 35: 271-278
  7. ↑ Imms, A.D. 1924. A General Textbook of Entomology. Methuen, London. (p. 183)
  8. ↑ C. P. Klingenberg and M. Zimmermann. 1992. Dyar's rule and multivariate allometric growth in nine species of waterstriders (Heteroptera: Gerridae). Journal of Zoology, London 227, 453–464.
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