— This glossary was compiled and edited by volunteer scientists from multiple scientific disciplines using reputable sources, including the references listed at the bottom of this page. If you don’t find the scientific word, term, or expression you are looking for, let us know in the comment section below, and we will research the word for you, and add it to the glossary. We desperately need editors to flesh this glossary out. If you are interested, please contact jerry.cates@entomobiotics.com:


  • yolk — material consisting of a mixture of lipids and proteins, secreted in the form of granules, that in eggs act as a source of food for the growth and development of an embryo.
  • yolk body (yolk platelet) — a membrane-bound storage structure containing protein and lipid, found in large numbers of cytoplasm of the eggs of all animals except mammals.
  • yolk sac — in the embryos of vertebrates, a sac arising as a diverticulum of the alimentary canal with which, except in the Teleostei, it communicates. In Reptilia, Aves, and Monotremata it contains yolk, which nourishes the embryo, and as the yolk is consumed the sac merges with the embryo. In Marsupialia, the sac contains no yolk, but absorbs nutrient from the uterine wall and in some cases forms a temporary placenta. In Eutheria the sac contains no yolk and most of it is cut off from the embryo at birth.


anat. = anatomy; arach. = arachnid; behav. = behavioral; biol. = biological (inclusive of all animals and plants); bot. = botanical (inclusive of all plants); Gr. = Greek; L. = Latin; q.v. = L. quod vide = which see; pl. = plural; taxon. = taxonomy; zool. = zoological (inclusive of all animals).


  1. Allaby, Michael, Ed. 1991. The Concise Oxford Dictionary of Zoology. Oxford Press.
  2. Beccaloni, Jan. 2009. Arachnids; Glossary, p. 319. University of California Press, p. 56.
  3. Gertsch, Willis J., 1979. American Spiders, 2nd Edition: Glossary, pp. 255-260. Von Nostrand Reinhold Company.
  4. Howell, W. Mike, and Ronald L. Jenkins. 2004. Spiders of the Eastern United States; Glossary, Chapter X, pp. 341-348. Pearson Education.
  5. Jackman, John A. 1997. A Field Guide to Spiders & Scorpions of Texas: Glossary pp. 173-177. Texas Monthly.
  6. Kaston, B. J. 1978. How to know the spiders: Index and Pictured Glossary, pp. 267-272. McGraw Hill Company.
  7. Preston-Mafham, Rod. 1996. The Book of Spiders and Scorpions; Glossary, pp. 140-141. Barnes & Noble Books, New York.
  8. Ubick, D., P. Paquin, P.E. Cushing and V. Roth, editors, 2005. Spiders of North America, Chapter 72: Glossary — pronunciation guide. Published by the American Arachnological Society.
  9. Venes, Donald, Ed. 2009. Taber’s Cyclopedic Medical Dictionary, 21st Ed. F.A. Davis Company, Philadelphia.
  10. Williams, Tim. 2005. A Dictionary of the Roots and Combining Forms of Scientific Words. Squirrox Press, Norfolk, England.


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