A Computerized Dictionary of Entomology

Thousands of Conceptually Cross-Referenced Terms about Insects and Other Arthropods

EXPLORE almost 4,000 entomological terms in alphabetical listings, computerized cross-references, and conceptual indexes: external anatomy (by body region), internal anatomy and physiology (by organ system), development, adaptive behavior, ecology, and insect control.

DISCOVER definitions, pronunciations, and concepts.

ENRICH biology, entomology, and zoology.


© 1995 Douglas Drenkow. All Rights Reserved.


“Dictionaries are like watches; the worst is better than none, and the best cannot be expected to go quite true.”
— Samuel Johnson (1709 – 1784)

The success of a social species — whether it walks on two legs or six — ultimately depends on good communication. To that end, prehistoric hominids invented spoken language; and ancient peoples, written. As the books from which the words in all others spring, rich with meaning, dictionaries were among the first forms of literature; and the progress of virtually every civilization on Earth has been reflected in and promoted by its development of dictionaries.

Likewise, the advancement of any given field of knowledge is utterly dependent upon mutual understanding not only amongst scientists in that field but also between them and those in all other fields with which they interface: Facilitating such unambiguous communication between entomologists and between entomologists and their interdisciplinary counterparts is the primary objective of this present work.

However, given the enormity and complexity of the science of entomology — and the intricate, often case-specific, and sometimes even self-contradictory vocabulary it has engendered (For example, see “mentum,” “frontal suture,” and the various forms of “social symbioses”) — this is much easier said than done.

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The work before you represents simply the best effort of its author to present in as coherent a fashion as possible a study of over 3900 of the terms employed in a goodly variety of excellent, often classic references, representing the major entomological subdisciplines (See the “Selected Bibliography” as well as the “Conceptual Indexes”).

As a specialty dictionary, this work does not attempt to present all meanings for the terms included: Definitions and context presented relate reliably only to entomology (and, where specified, to the zoology of related invertebrates), and other meanings for many of these terms may be found elsewhere. The reader is encouraged to consult not only general dictionaries of the English language but also any of the widely available dictionaries on science and technology, biology, and zoology as well as any of the likewise excellent dictionaries, glossaries, and encyclopedias published for such specific topics as genetics or pesticides (In addition, the proper governmental agencies should be consulted for laws and regulations governing pesticides — this dictionary is not to be considered in any way legally authoritative).

Please note, too, that this abridged dictionary of entomology omits virtually all specific names, for people, organizations, pesticides, and organisms: Given the fact that an unabridged dictionary of the entire English language contains some 450,000 words but that there are over 750,000 described species of insects — each of which is identified by at least one binomial as well as a host of higher taxonomic names and often one or more common names — it should be appreciated that entomological nomenclature is a subject beyond the scope of this particular work.

One group of terms included herein is not strictly entomological, although they are routinely used by entomologists (and other scientists), especially in coining new terms: Prefixes and suffixes, whose meanings — and shades of meaning — are as illuminating as they are useful. Students of “etymology” (the evolution of words) should take note, however, that some of the terms identified herein as “prefixes” or “suffixes” (such as “neur-,” as in “neuron,” or “-gaeic,” as in “epigaeic”) are actually “combining forms”, used in forming compound words and more able to stand alone than true “affixes.”

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Each entry is identified by a code — a “letter-number” (such as “a1” or “c123”) — which is used consistently throughout the text entries, cross-references, and alphabetical and conceptual indexes and whose entry from your computer keyboard will be requested at appropriate times by the program accessing the data-base (See “Program Notes”).

The spelling of each term represents either the standard spelling for that term or a common variation (in which case there is a cross-reference to the more common and/or proper spelling).

See “Key to Pronunciations” for interpreting the phonetic pronunciations presented.

Parts of speech are indicated (verb, adverb, adjective, or noun); and although conjugations of verbs are not included (They typically follow standard rules of English), plurals for nouns (and for suffixes for nouns) are presented, especially because so many are formed in accordance with the rules of Latin (ex. “bursa” to “bursae”).

Definitions are to be taken in an entomological context — that is, they apply to insects and only to insects, unless otherwise specified. Moreover, especially given the unsurpassed variety of insects, no definition should be assumed to necessarily apply to all insects, to most insects, or even to all or most members of any taxon specified (as in “In Diptera, this structure is...”): Consult entomological texts for assessing the applicability of any given definition to any given species.

Cross-references are included liberally throughout the text entries: Ultimately, virtually all terms can be defined in terms of other terms; and when prompted, entering the desired “letter#” for your next entry or pressing “Home” for your last entry (See “Program Notes”) allows you great freedom to pursue your own “trains of thought”.

Bon voyage!

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Selected Bibliography

Borror, Donald J., Dwight M. De Long, and Charles A. Triplehorn, An Introduction to the Study of Insects, Fifth Edition, Saunders College Publishing, San Francisco, CA, 1981.

Borror, Donald J., and Richard E. White, A Field Guide to the Insects of America North of Mexico, Houghton Mifflin Company, Boston, MA, 1970.

Brues, Charles T., and A. L. Melander, Classification of Insects, Museum of Comparative Zoology, Harvard University, Cambridge, MA, 1932.

Chapman, R. F., The Insects: Structure and Function, Third Edition, Harvard University Press, Cambridge, MA, 1982.

Gove, Philip Babcock, Editor-in-Chief, Webster’s Third New International Dictionary of the English Language Unabridged, G. & C. Merriam Company, Springfield, MA, 1971.

Holmes, Sandra, Henderson’s Dictionary of Biological Terms, Van Nostrand Reinhold Company, San Francisco, CA, 1979.

Knipling, E. F., The Basic Principles of Insect Population Suppression and Management, Agriculture Handbook No. 512, United States Department of Agriculture, Washington, DC, 1979.

Leftwich, A. W., A Dictionary of Entomology, Crane Russak & Company, Inc., New York, NY, 1976.

Lehninger, Albert L., Biochemistry, Second Edition, Worth Publishers, Inc., New York, NY, 1975.

Little, V. A., General and Applied Entomology, Third Edition, Harper & Row, Publishers, San Francisco, CA, 1972.

Martin, E. C., E. Oertel, N. P. Nye, et al., Beekeeping in the United States, Agriculture Handbook No. 335, U.S. Department of Agriculture, Washington, DC, 1980.

Morris, Christopher, Editor, Academic Press Dictionary of Science and Technology, Academic Press, Inc., San Diego, CA, 1992.

Oldroyd, Harold, Collecting, Preserving, and Studying Insects, Hutchinson Scientific and Technical, London, UK, 1958.

Snodgrass, R. E., Principles of Insect Morphology, First Edition, McGraw-Hill Book Company, Inc., NY, 1935.

Swan, Lester A., and Charles S. Papp, The Common Insects of North America, Harper and Row, Publishers, San Francisco, CA, 1972.

Sweetman, Harvey L., The Principles of Biological Control, Wm. C. Brown Company, Dubuque, IA, 1958.

Villee, Claude A., Warren F. Walker, Jr., and Robert D. Barnes, General Zoology, Fourth Edition, W. B. Saunders Company, Philadelphia, PA, 1973.

Ware, George W., Complete Guide to Pest Control — With and Without Chemicals, Thomson Publications, Fresno, CA, 1980.

Wigglesworth, V. B., The Life of Insects, The World Publishing Company, New York, NY, 1964.

Wilson, Edward Osborne, The Insect Societies, The Belknap Press of Harvard University Press, Cambridge, MA, 1971.

Winston, Mark L., The Biology of the Honey Bee, Harvard University Press, Cambridge, MA, 1987.

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Sample Entries: A1 – A25

Note: Numbers in brackets are computerized cross-references (precursors of modern-day hyperlinks).

A1) A



In a wing, any of typically 3 anal veins [a133], labeled (from front to back): “1A,” “2A,” and “3A”. Unlike other major longitudinal veins [l103], the anal veins are typically unbranched.

In a wing, a corresponding anal cell [a117], located just behind and named for one of these anal veins: “1A,” “2A,” or “3A”.

A2) A-



Indicating not or without; as in acephalous [a12], alecithal [a80], ametabolous [a102], apneustic [a224], apterous [a242], asexual [a276], or asymmetrical [a285]. See also in- [i13] and pseud- [p443], and compare eu- [e167].


AB-duh- (ab-DOH-) (ub-DOH-) -mun

Noun, plural: ABDOMENS or ABDOMINA [“ab-DOM-uh-nuh”]

In general, the posterior (rearmost) tagma [t9] (body region). See the conceptual index to The Abdomen for terms describing specific topics relating to this tagma in insects and the comparable tagmata in other arthropods, each of which is composed of the ancestral pygidium [p496] — the periproct [p74], bearing the anus (Compare prostomium [p416]) — fused with several of the true segments [s80] of the ancestral trunk (generated one-by-one ahead of the pygidium).

In an insect, the posterior of the 3 major divisions of the body; the division behind the head [h29] and the thorax [t91], containing most of the major internal organs [o76] and consisting of 11 or fewer segments (the 10th and 11th typically much reduced or modified). The first 7 segments of the abdomen bear paired appendages only in the immature stages of various orders (gills [g56], filaments [f30], or prolegs [p388]) or in the adult stages of apterygotes [a245] (styli [s349], collophores [c206], etc.) or Odonata (genitalia [g36]). The 8th and 9th segments bear the genitalia in most orders of insects. The 10th segment may bear an epiproct [e132], cerci [c85], or paraprocts [p26] (all remnants of the degenerate 11th segment). The generalized abdomen of an insect is presumably derived from the 8th through 18th segments behind the head plus the pygidium of an ancestral arthropod (See segment [s80]); however, this number of segments is often much reduced in modern forms (By contrast, in some embryonic insects as well as in adult proturans, so-called half-insects [h11], the abdomen contains 12 segments [s80], the last actually the periproct). The abdomen is occasionally called the metasoma [m126] (Compare mesosoma [m109]) or the gaster [g13], although this latter term is better reserved for that portion of the abdomen of an ant behind the pedicel [p53] (the “wasp-waist”).

In a chelicerate, the posterior of the 2 major divisions of the body (behind the cephalothorax [c82], or prosoma [p414]), often appearing unsegmented (as in spiders) and typically with few or no paired appendages; also called the opisthosoma [o62]; presumably derived from the 7th through 18th segments behind the head plus the periproct of an ancestral arthropod.

In a typical crustacean, the posterior of the 2 major divisions of the body (behind the cephalothorax [c82], or prosoma [p414]), segmented (as in the “tail” of a lobster) and sometimes (in amphipods, isopods, and especially decapods) bearing such paired, typically unleglike appendages as gonopods [g84], swimmerets [s440], and uropods [u22] as well as a single telson [t42]; also called opisthosoma [o62]; presumably derived from the 13th through 18th segments behind the head plus the periproct of an ancestral arthropod.


ab-DUK-tur (-Tor)

Noun, plural: ABDUCTORS or ABDUCTORES [“Ab-Duk-TOR-eez”]

Any muscle whose contraction pulls a movable body part away from the midline of the body or from the centerline of an appendage [a235]. See also extensor [e200], protractor [p436], and promotor [p394] as well as levator [l75]; and compare adductor [a36], flexor [f54], and retractor [r95] as well as depressor [d36].


ub- (ab-) -SORP- (-ZORP-) -shun

Noun, plural: ABSORPTIONS

Penetration of a substance into an object, as said of digested foodstuffs being absorbed in the midgut [m155] of an insect, pesticides [p88] being absorbed through the exoskeleton [e196] (protected by the waxy epicuticle [e108]) of a pest, or gases being absorbed throught the body wall [b111] of an aquatic insect (See gill [g56]). Compare adsorption [a49] as well as holocrine secretion [h87] and merocrine secretion [m77].



Noun, plural: ACARICIDES

A pesticide [p88] that kills (or otherwise controls) mites and/or ticks; typically synonymous with miticide [m173].


ik- (ak-) (uk-) -SES-ree (-uh-ree) Sel


In many Lepidoptera, a closed cell [c173] (typically the R2 cell [r1] [“2” is a subscript]) between 2 fused branches of the radius [r13] (that is, just in front of the tip of the discal cell [d88] in the forewing).

In general, any atypical cell [c70] in a wing.


ik- (ak-) (uk-) -SES-ree (-uh-ree) Gland


In the reproductive system of a male insect, each of the pair of mucous glands [m221], derived either from the ectoderm [e18] (forming an ectadenium [e16]) or mesoderm [m99] (forming a mesadenium [m87]), that typically open into upper end of the ejaculatory duct [e35] (where it meets the lower ends of the vasa deferentia [v11]) and secrete the fluid that serves as semen [s93] (to carry the spermatozoa) or hardens into a spermatophore [s225] (a sperm capsule). See also conglobate gland [c246] as well as corpus allatum [c280].

In the reproductive system of a female insect, each of the pair of glands, derived from the ectoderm, that typically open into the posterior end of the vagina [v1] (or on the underside of the 9th segment of the abdomen, between the bases of the second valvifers [v4]) and secrete a substance that “glues” eggs to a substrate or to one another or that hardens into an ootheca [o52] (an egg case); also called colleterial gland [c205] (particularly if secreting a “gluey” substance). Note that some accessory glands are modified as stink glands [s312]; others (such as the acid gland [a16] of a bee sting [b48]), as venom [v21] glands.


ik- (ak-) (uk-) -SES-ree (-uh-ree) Hart


Any of various membranous, typically saclike and valved, pulsating organs found by the base of the antennae, wings, or legs or within the legs of various insects and augmenting the circulatory powers of the true heart [h32], by pumping blood [b105] into these appendages (including into the veins [v14] of the wing); also called pulsatile organ [p478] or pulsating membrane [p479].


ik- (ak-) (uk-) -SES-ree (-uh-ree) Vane


In general, any secondary branch of a longitudinal vein [l103] in a wing (Ex. Cu1a [c335] [“1a” is a subscript] or Cu1b [“1b” is a subscript], each of which is an end branch of Cu1 [“1” is a subscript], the first branch of Cu [c335]). Compare adventitious vein [a55], including supplement [s415] and spurious vein [s267], and intercalary vein [i86] — none of which is a branch of an existing longitudinal vein.

In Symphyta (primitive Hymenoptera), the longitudinal vein running along the rear side of a lanceolate cell [l28] in the fore- and hind-wings. Although this vein (also called the lanceolate vein [l29] or subanal vein [s354]) may be termed the most posterior vein in the anal area of the wing [a116] (and designated “2A” or “3A,” according to different interpretations), the axillary vein [a313] actually lies more posteriorly.


Ak-suh-DENT-ul PARE-uh-Sy- (-sih-) -Tiz-um


Incidental parasitism [i20].


ay-SEF- (AY-sef-) (uh-SEF-) -uh-lus


Without a (well-defined) head [h29], said of various larvae, particularly maggots [m9]. Compare eucephalous [e168] and hemicephalous [h41].


ay-SEER-us (AY-Seer-us)


Without antennae [a166], said of proturans (half-insects [h11]). Compare brachycerous [b129].


uh-SET-ul- (AA-suh-Teel-) -KOH- (-KAW-) -leen


Biochemical substance that carries nerve impulses [n34] across various synapses [s449] (the gaps between neurons [n60] or between neurons and effectors [e27]), in insects, other animals, and human beings; targeted for interference by many chemical pesticides [p88], acting as nerve-poisons (See acetylcholinesterase [a15]).


uh-Seet-ul-Koh- (-Kaw-) -Leen-ES-tuh-Rase (-Raze)


The enzyme in the body of insects, other animals, and human beings that breaks down acetylcholine [a14], which transmits nerve impulses [n34] across various synapses [s449] (between neurons [n60] or between neurons and effectors [e27]); also called cholinesterase [c125]. Such pesticides as carbamate insecticides [c35] and organophosphate insecticides [o79], such stimulating drugs as cocaine and caffeine, or such neurotoxins [n64] as the venoms [v21] of various arthropods act as anticholinesterases [a207], nerve poisons that interfere with the action of acetylcholinesterase — the targeted (or accidentally poisoned) creature typically goes into convulsions, as its nerves continue to “fire”, out of control. See also tonus [t109].


AA-sid Gland

Noun, plural: ACID GLANDS

The main venom [v21] gland of a bee sting [b48], secreting apitoxin [a223]; the venom sac (which, with the alkaline gland [a90], remains attached to the barbed sting, inserted into the victim, even if a worker [w36] bee tears itself away — see altruism [a98]).


AY-Koan I

Noun, plural: ACONE EYES

A compound eye [c233] without (well-developed) crystalline cones [c331], as in a crane fly. Compare eucone eye [e169], exocone eye [e189], and pseudocone eye.



Noun, plural: ACRAEINS

A defensive secretion [d16] of various butterflies (of Lepidoptera) that is distasteful to predators [p328] (probably primarily birds) or is otherwise protective. See also aposematic [a233] as well as mimicry [m165].

A19) ACRO-

Ak-roh- (-ruh-)


Indicating highest, uppermost, outermost; as in acrosternite [a21], acrostichal bristle [a22], or acrotrophic egg tube [a24]. See also dorso- [d127], epi- [e104], hyper- [h151], not- [n82], super- [s403], supra- [s418], and -vertical [v51]; and compare -base [b22], basi- [b24], hyp- [h149], hypo- [h159], infra- [i34], pedi- [p52], -podium [p213], stern- [s290], sub- [s350], and ventr- [v25] as well as latero- [l49] and pleuro- [p190].


AA-Kron (-krun)

Noun, plural: ACRONS

Prostomium [p416].



Noun, plural: ACROSTERNITE

The narrow flange lying just behind the intersegmental membrane [i99] but just in front of the (transverse) antecostal suture [a163] in the sternum [s302] (the sclerotized underside) of a body segment in various arthropods, as in each segment in the abdomen typical of insects. Compare poststernite [p304] and acrotergite [a23] as well as presternum [p347] and spinasternum [s238], and see also secondary segmentation [s67].


uh-KROS-tik-ul BRIS-ul


In muscoid flies (higher Diptera), each of the many small bristles [b141] in one to several rows running along the midline of the mesonotum [m101] (and, thus, just to the inside of the dorsocentral bristles [d128]).



Noun, plural: ACROTERGITES

The small to large flange lying just behind the intersegmental membrane [i99] but just in front of the (transverse) antecostal suture [a163] in the tergum [t62] (the sclerotized upperside) of a body segment in various arthropods. Compare posttergite [p305] and acrosternite [a21], and see secondary segmentation [s67] and postnotum [p296].


Ak-roh-TRAW- (-TROH-) -fik Eg (Ayg) Toob (Tyoob)


An egg tube [e34] (within an acrotrophic ovariole [a25], as in certain plant bugs, beetles, and fleas) whose trophocytes [t180] (nurse cells [n97]) lie in the (upper) end chamber [e58] (the germarium [g45]) and provide nutrition to the oocytes [o49] (eggs developing in the vitellarium [v73], or zone of growth [z3]) via “nutritive cords” (protoplasmic connections between oocytes and trophocytes produced from the division of the same oogonium [o50]); also called telotrophic egg tube [t40]. Compare polytrophic egg tube [p254] — the other type of meroistic egg tube [m78] — as well as panoistic egg tube [p12], and see also apical cell [a220] (in some male insects).


Ak-roh-TRAW- (-TROH-) -fik oh-VARE-ee-Ole


An ovariole [o91] with an acrotrophic egg tube [a24].

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