Termite Basics: Morphology

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This page lists the parts of a termite that can actually be seen and counted: the Chinese name used on this site, the Latin/English term, the caste in which it occurs, and what to look for. Entries are compiled from the archived volumes of Fauna Sinica, Insecta Vol. 17, Isoptera (Huang Fusheng et al., 2000), Termitology (Cheng Dongbao & Yang Zhaofen, 2014), Biology of Termites: A Modern Synthesis and Krishna et al. (2013), Treatise on the Isoptera of the World. Terminology follows the site glossary (_data/translation_glossary.yml) so that it matches the checklist and the morphological descriptions on the family, genus and species pages.

Termites are front-headed (prognathous) insects with chewing mouthparts, divided into head, thorax and abdomen. Adults are usually a few millimetres to just over a centimetre long; alates reach 10–30 mm including the wings; a long-lived queen, with her abdomen enormously distended, may reach 60–70 mm, and a few African species exceed 100 mm. Castes of the same species differ so much that every description must state which caste is being described — the reason identification keys are always split into alates and soldiers.

This page covers external morphology and the main internal organs only; names and distributions of taxa are in the checklist, and identification runs through the morphological descriptions on the family, genus and species pages; where a species text has not yet been checked, the page gives the original description citation and links to its genus page. The site has withdrawn the Fauna Sinica family and genus keys; only the order and Termitidae subfamily key on the checklist and the world genus key on the Kalotermitidae page remain.

• 1. Castes
• 2. Head
• 3. Thorax, wings and legs
• 4. Abdomen
• 5. Soldier-specific structures
• 6. Internal organs
• 7. Using these terms with descriptions and keys
• 8. Names, synonyms and sources

1. Castes

Two large groups are recognised by function first: the reproductive and the non-reproductive castes. Within them the castes are separated by developmental origin — the same name may arise along different routes in different groups (supplementary reproductives especially), so read the table with both form and developmental origin in mind.

Group	Caste	Form and development
Non-reproductive	white immature	White, unsclerotised, without soldier features; fed by nestmates. Those without external wing buds are white larvae, those with them white nymphs
Non-reproductive	larva (dependent larva)	No external wing buds, cannot feed itself; darker and older than the white larva, with no sharp boundary — calling the white larva a larva is also correct and widely accepted
Non-reproductive	pseudergate (false worker)	Feeds itself; wing buds shortened or gradually lost; develops from the larva or by regressive moult from the nymph; in groups without true workers (Kalotermitidae etc.) it is the main workforce
Non-reproductive	worker	Develops along the wingless route; wingless (wing buds occur as rare abnormalities), eyes strongly reduced; some species have size and sex castes among workers
Non-reproductive	presoldier	Soldier-like head but unpigmented and weakly sclerotised, cannot defend; an instar on the way to the soldier from other castes
Non-reproductive	soldier	Head heavily sclerotised; mandibles enlarged (mandibulate) or the head drawn out into a nasus with reduced mandibles (nasute); cannot moult or reproduce, cannot feed itself; some species have size and sex castes among soldiers
Non-reproductive	nymph	Immature with external wing buds that grow with age; normally develops into the alate
Reproductive	alate	Two complete wing pairs, dark, compound eyes and ocelli well developed; wings break off at the wing scale after the dispersal flight
Reproductive	dealate	Wings shed, scales retained; pairing after the flight makes it a primary reproductive
Reproductive	primary reproductive (king, queen)	From a dealate pair founding a nest; pigmented, eyes well developed, wing scales present; in many species the queen becomes physogastric with exposed intersegmental membranes
Reproductive	adultoid	Resembles the primary reproductive; developed from an alate that did not fly and shed its wings inside the nest, mostly in Termitidae
Reproductive	neotenic: brachypterous, squamate, apterous	Wing buds present and growing, classed as long-, short- and micro-brachypterous; those that have shed the wings and keep only scales are squamate; wingless forms are apterous; they do not fly and replace the primary king and queen in the nest
Reproductive	neotenic: larvoid, pseudergatoid, nymphoid, ergatoid, reproductive soldier	In groups without true workers, larvoid (from larvae) and pseudergatoid (from pseudergates); in groups with true workers, nymphoid (from nymphs, wing buds retained) and ergatoid (from workers, no wing buds); the reproductive soldier is known only in Archotermopsidae

Castes are not a fixed ladder but branches split by developmental route. Termites have three kinds of moult — progressive, stationary and regressive — and the last returns the individual to an earlier instar. In one-piece nesters (Kalotermitidae etc.) a pseudergate can moult progressively into a nymph, presoldier or neotenic, or hold its form by a stationary moult, while a nymph can regress to a pseudergate. The larva of Mastotermes darwiniensis may reach the alate through a nymph or become a worker or presoldier directly. In the remaining, multiple-piece nesters the larva takes one of two routes: the nymphal line leads to alates, nymphoid and adultoid reproductives, the wingless line to workers, presoldiers and soldiers, and a worker can still become an ergatoid.

Castes also diversify within themselves. Hospitalitermes medioflavus has three worker forms and one soldier form: minor workers are all male, medium and major workers all female; minor workers pass through a presoldier to become soldiers and medium workers can grow into major workers; major workers only carry food, minor workers gather lichens, soldiers scout and defend. Macrotermes soldiers are major and minor; M. annandalei and M. barneyi keep major and minor workers in the same nest. Supplementary reproductives differ between groups and even within a genus: most Termitidae produce them, Macrotermes bellicosus has adultoids while M. subhyalinus has none, Odontotermes obesus produces them while O. assmuthi does not; whether O. formosanus can produce them has long been debated, and most authors think not.

Neotenic reproductives carry two parallel nomenclatures: one by wing development (brachypterous, squamate, apterous), one by source caste (larvoid, pseudergatoid, nymphoid, ergatoid, reproductive soldier). The two are not exclusive — nymphoids usually keep wing buds, ergatoids have none, squamates have lost the buds and keep only scales — and papers often give only one set, so check which is meant.

2. Head

The head capsule is round, oval, square or pear-shaped and prognathous. Its most conspicuous feature is the epicranial suture: a transverse (ecdysial) line and a median longitudinal line meeting in a T or Y. Many species show it only faintly. The area in front of the transverse line is the frons; behind it lies the vertex, and behind that the occiput. In Rhinotermitidae and Termitidae the junction of the two lines is often depressed or raised and opens as the fontanelle, the opening of the frontal gland and one of the hallmarks of Neoisoptera.

The compound eyes sit on the sides of the head. They are large in alates — about 200 ommatidia per eye in Mastotermes, 300–400 in Coptotermes formosanus and about 360 in Odontotermes formosanus — and reduced to a pigment patch or lost entirely in workers and soldiers. The single pair of ocelli lies above or anterodorsally to the compound eyes, whitish and translucent; they occur only in reproductives, and are missing even there in a few groups.

Antennae are moniliform or oval with 9–30+ segments; beyond the scape and pedicel, the third segment is often split, producing an “incomplete division” that must be allowed for when counting.

Mouthparts are of the chewing type: the labrum covers the mouth; the clypeus is divided into a soft anteclypeus and a sclerotised postclypeus (often with a median groove in Rhinotermitidae and Termitidae); the paired mandibles carry an apical tooth, marginal teeth and a basal molar plate; each maxilla has a cardo, stipes, galea, lacinia and a 5-segmented palp; the labium has a postmentum, prementum, glossa, paraglossa and 3-segmented palps. The mouth cavity is enclosed by the labrum, mandibles, maxillae and labium, with the hypopharynx forming its floor.

Name	Latin / English	Notes
Head capsule	head capsule	The whole head skeleton; soldier head shape (square, oblong, pear-shaped, conical) is widely used in genus keys
Epicranial suture	epicranial suture	Transverse and longitudinal lines, T- or Y-shaped; the median line runs forward over the vertex
Frons	frons	Central area in front of the transverse line; in nasute soldiers the frons is drawn out as the nasus
Vertex	vertex	Dorsal area between the transverse line and the occiput
Occiput	occiput	Rear of the head; the occipital foramen transmits the neck, nerve cord and gut
Occipital foramen	occipital foramen	The large posterior opening of the head
Gena	gena	Lateral area below and behind the compound eye; often expanded or toothed in soldiers
Compound eye	compound eye	Made of ommatidia; large in alates, reduced or absent in workers and soldiers
Ocellus	ocellus	One pair, above or anterodorsal to the compound eyes; usually only in reproductives
Antenna	antenna	Moniliform; 9–30+ segments, fewer in soldiers
Scape	scape	First antennal segment, the stoutest
Pedicel	pedicel	Second antennal segment
Flagellum	flagellum	Segment 3 onward; segment 3 is often split
Antennal socket	antennal socket	Membranous pit on the frons where the antenna articulates
Labrum	labrum	Front flap of the mouthparts, tongue-shaped; soldier labrum may be tongue-shaped, bifid, asymmetric or grooved
Clypeus	clypeus	Sclerite above the labrum, divided into ante- and postclypeus
Anteclypeus	anteclypeus	Anterior, membranous part of the clypeus
Postclypeus	postclypeus	Posterior, fully sclerotised part; often grooved in Rhinotermitidae and Termitidae
Epipharynx	epipharynx	Inner (labral) wall of the mouth, bearing regular small spines
Mandible	mandible	Paired, with anterior and posterior articulations; apical tooth, marginal teeth and molar plate
Apical tooth	apical tooth	The terminal tooth; the reference point for the mandibular index
Marginal tooth	marginal tooth	Teeth on the inner mandibular edge, numbered 1, 2 … from the apex
Molar plate	molar plate	Basal grinding surface of the mandible, often ridged
Left mandibular index	left mandibular index	Distance from apical tooth to first marginal tooth ÷ distance from first to second marginal tooth; a standard measurement
Mandibular dentition	mandibular dentition	Number and arrangement of teeth; often asymmetric in soldiers, with more teeth on the left
Maxilla	maxilla	Paired; cardo, stipes, galea, lacinia and maxillary palp
Cardo	cardo	Basal segment articulating with the head
Stipes	stipes	Main body of the maxilla
Galea	galea	Flattened, two-segmented lobe covering the lacinia laterally
Lacinia	lacinia	Inner lobe with two apical teeth and a row of spiniform setae
Maxillary palp	maxillary palp	Five segments, inserted on the stipes
Labium	labium	Postmentum, prementum, glossae, paraglossae and labial palps; forms the rear wall of the mouth
Postmentum	postmentum	Formerly called gula; elongated in soldiers and its shape follows the head shape — a genus-level character
Prementum	prementum	Bears the glossae, paraglossae and labial palps
Glossa	glossa	Inner pair of apical lobes of the prementum
Paraglossa	paraglossa	Outer pair of apical lobes of the prementum
Labial palp	labial palp	Three segments
Hypopharynx	hypopharynx	Floor of the mouth; sensory and food-transporting
Mouth	mouth	Cavity enclosed by labrum, mandibles, maxillae and labium, leading to the cibarium and pharynx
Cibarium	cibarium	Cavity between mouth and pharynx, start of the foregut
Fontanelle	fontanelle	Opening of the frontal gland at the epicranial junction or on the frons; absent in most lower groups, present in Rhinotermitidae and Termitidae
Frontal gland	frontal gland	Sac-like gland in the head, defensive; nasute soldiers eject its secretion
Tentorium	tentorium	Internal head skeleton for muscle attachment; its pits mark the head surface
Neck	cervix	Short membranous region between head and thorax

3. Thorax, wings and legs

The thorax has three segments: pro-, meso- and metathorax. The pronotum is free and shield-like, and highly variable — transverse-rectangular, semicircular, trapezoidal, or saddle-shaped with the front raised and the sides deflexed; its front and rear margins are often notched. The meso- and metanota are associated with the pterothorax. The prosternum is reduced; the mesosternum is the most developed and roughly triangular. Anterior and posterior notal wing processes connect to the wing base through the axillary sclerites.

There are two pairs of membranous, elongate wings, folded flat over the abdomen at rest, the forewing usually a little longer than the hindwing — hence “Isoptera”, although they are not truly equal. Wing vestiture differs by family: wings are bare (or with microtrichia only) in Mastotermitidae, Kalotermitidae and Hodotermitidae, hairy in Coptotermes. Mastotermitidae and Hodotermitidae have a reticulate membrane with fine cross-veins; only Mastotermitidae have a large anal lobe on the hindwing. After the dispersal flight the wings break off along the humeral (basal) suture, leaving triangular wing scales: the forewing scale is distinctly larger than the hindwing scale in Kalotermitidae and Rhinotermitidae, but about equal in Termitidae.

The three pairs of legs have short coxae and trochanters and long femora and tibiae; the tibia bears a row of stout spines laterally and 2–3 apical spurs, summarised as the tibial spur formula (3:3:3, 3:2:2, 2:2:2 …). The tarsus is usually 4-segmented; 5 in Mastotermitidae, 5 ventrally but 4 dorsally in Archotermopsidae (tarsomere 2 reduced and visible only ventrally), and 3 in Stylotermes and Indotermes. The pretarsus ends in a pair of curved claws; some Kalotermitidae have an arolium.

Name	Latin / English	Notes
Prothorax	prothorax	First thoracic segment; pronotum free
Mesothorax	mesothorax	Second thoracic segment; bears forewings and mid legs
Metathorax	metathorax	Third thoracic segment; bears hindwings and hind legs
Pterothorax	pterothorax	Meso- plus metathorax, specialised for flight
Pronotum	pronotum	Free shield; shape (rectangular, semicircular, trapezoidal, saddle-shaped) and setae are genus/species characters
Mesonotum	mesonotum	Separated from the pronotum, close to the metanotum
Metanotum	metanotum	Last thoracic notum
Tergum / notum	tergum / notum	Dorsal plate of a segment
Pleuron	pleuron	Lateral plate of a segment
Sternum	sternum	Ventral plate; prosternum reduced, mesosternum triangular
Anterior notal wing process	anterior notal wing process	Anterior wing articulation on the pterothoracic notum
Posterior notal wing process	posterior notal wing process	Posterior wing articulation
Axillary sclerites	axillary sclerites	Small plates linking wing base to the notal processes
Wing	wing	Membranous, two pairs; fore- and hindwing similar in shape and venation
Forewing	forewing	On the mesothorax; usually slightly longer
Hindwing	hindwing	On the metathorax; anal lobe large only in Mastotermitidae
Anal lobe	anal lobe	Expanded posterior hindwing area, well developed in Mastotermitidae
Humeral (basal) suture	humeral suture / basal suture	The break line along which the wing is shed
Wing scale	wing scale	Triangular wing base left after shedding; fore/hind scale ratio separates families
Costa	costa (C)	Anterior marginal vein
Subcosta	subcosta (Sc)	Vein behind the costa
Radius	radius (R)	Median longitudinal vein; fused with Rs in Rhinotermitidae and Termitidae
Radial sector	radial sector (Rs)	Branch of the radius; many branches in Kalotermitidae
Media	media (M)	Variable in origin (from R, from Cu, or independent)
Cubitus	cubitus (Cu)	Posterior longitudinal vein, richly branched, thick basally
Anal vein	anal vein (A)	Vein of the anal area; usually lost in Rhinotermitidae and Termitidae
Cross-vein	cross-vein	Short vein connecting longitudinals; membrane reticulate in Mastotermitidae and Hodotermitidae
Wing microsculpturing	microsculpturing	Under SEM: papillae, tubercles and peg-like projections, plus short hairs
Coxa	coxa	First leg segment, articulating with the thorax
Trochanter	trochanter	Short segment between coxa and femur
Femur	femur	One of the longest leg segments
Tibia	tibia	Bears lateral spines and apical spurs
Tibial spur	tibial spur	Stout apical spine; its formula separates families
Tarsus	tarsus	Composed of tarsomeres; segment count is the first step in family keys
Tarsomere	tarsomere	Individual tarsal segment; usually 4, 5 in Mastotermitidae, 3 in Stylotermes and Indotermes
Tarsal claw	tarsal claw	Paired curved claws at the tip of the tarsus
Arolium	arolium	Pad between the claws; present in some Kalotermitidae
Wing pad	wing pad	Wing rudiment of nymphs; may remain short in brachypterous reproductives

4. Abdomen

The abdomen has 10 segments, cylindrical to olive-shaped, with tergites and sternites joined by membrane so that it can expand — this is how a queen’s abdomen becomes physogastric. Spiracles occur on segments 1–8; sternite 1 is reduced or lost. Tergite 10 tapers and overhangs the anus as the supra-anal plate (epiproct); sternite 10 is paired and divided medially as the paraprocts. In females sternite 7 is enlarged, rounded behind and covers sternites 8 and 9 as the subgenital plate. The male gonopore opens between sternites 9 and 10, and in primitive groups sternite 9 carries a pair of unsegmented styli. A pair of cerci lies beside sternite 10: usually 2 segments, but 5–8 in Mastotermitidae and some primitive taxa. An ovipositor (three pairs of valves) occurs only in female Mastotermitidae.

Reproductives often show brownish patches on the abdomen bearing short, erect yellow secretory setae; their secretion attracts workers to lick it and may play a role in caste formation. The sternal gland lies at the base of sternite 5 in workers of Kalotermitidae, Rhinotermitidae and Termitidae, on sternites 3–5 in Mastotermitidae, and on sternite 4 in Hodotermitidae and Archotermopsidae.

Name	Latin / English	Notes
Abdomen	abdomen	10 segments; tergites and sternites joined by membrane
Tergite	tergite	Dorsal abdominal plate; tergites 1–9 similar, transversely rectangular
Sternite	sternite	Ventral abdominal plate; sternite 1 reduced or lost
Intersegmental membrane	intersegmental membrane	Connects tergites and sternites; exposed in physogastric queens
Spiracle	spiracle	One pair on segments 1–8; 6 pairs recorded in fully physogastric queens
Supra-anal plate	supra-anal plate (epiproct)	Tergite 10, overhanging the anus
Paraproct	paraproct	Sternite 10, paired and divided medially
Subgenital plate	subgenital plate	Female sternite 7, enlarged and covering sternites 8–9
Stylus (pl. styli)	stylus (pl. styli)	Paired unsegmented processes on the posterior margin of sternite 9 in lower termites; may occur in both sexes or in one
Cercus (pl. cerci)	cercus (pl. cerci)	Paired, beside sternite 10; usually 2-segmented, 5–8 in Mastotermitidae
Ovipositor	ovipositor	Only in female Mastotermitidae; three pairs of valves
Gonopore	gonopore	Male: between sternites 9 and 10; female: beneath sternite 7
Secretory setae	secretory setae	Short erect yellow setae on the abdomen of reproductives
Sternal gland	sternal gland	Trail pheromone source; location varies by family (see above)
Tergal gland	tergal gland	Gland beneath the tergites, involved in recognition and aggregation
Posterior sternal gland	posterior sternal gland	Hind-abdominal gland active during dispersal and pairing
Anus	anus	Opening of the hindgut, between epiproct and paraprocts

5. Soldier-specific structures

Soldiers are the “soldier plan”: head capsule and mandibles highly specialised, antennal segments often fewer, compound eyes reduced to traces. Two main types are recognised. Mandibulate soldiers have enormous mandibles and a head capsule that does not project forward; the inner teeth of the left and right mandibles often differ, and in some genera (e.g. Capritermes) the mandibles are twisted into a strongly asymmetric “snapping” bite. Nasute soldiers have reduced mandibles and a head drawn out into a long nasus, with the fontanelle opening at its tip and ejecting a sticky secretion (e.g. Nasutitermes). A few genera are intermediate, such as Armitermes, sometimes called nasutoid.

Soldier heads are square, oblong, round, oval, pear-shaped or conical. In Cryptotermes the head is short, thick and raised in front, plugging the gallery opening — phragmosis. The epicranial suture is often Y-shaped or reduced to the median line. The frons may be flat or raised, and in nasute soldiers it becomes the nasus. The fontanelle varies: absent in many lower termites; a large circular pore on the front of the head in Coptotermes, which secretes a milky acidic fluid (hence the Chinese name “milk-exuding termite”); at the nasus tip in Nasutitermes. Labral shape is a standard character: tongue-shaped in lower groups, bifid or asymmetric in Termitidae, and extremely long and grooved in Schedorhinotermes, where it can cover the mandible tips and the groove leads to the fontanelle.

The ratio of pronotal width to head width is also used: the pronotum is wider than or about as wide as the head in Kalotermitidae, slightly narrower in Rhinotermitidae, and much narrower in Termitidae. In Reticulitermes soldiers, the number of setae in the middle of the pronotum separates the “raised-frons” group (more than 20 setae) from the “flat-frons” group (about 10 or none).

Name	Latin / English	Notes
Mandibulate soldier	mandibulate soldier	Enlarged mandibles, head not projecting; defence by biting and frontal-gland secretion
Nasute soldier	nasute soldier	Mandibles reduced, head produced into a nasus, fontanelle at its tip
Nasutoid soldier	nasutoid soldier	Intermediate: mandibles reduced but nasus short
Nasus	nasus	Tubular forward extension of the frons in nasute soldiers
Phragmosis	phragmosis	Head modified as a plug for the nest opening, as in Cryptotermes
Frontal pore	frontal pore	Opening of the frontal gland; at the nasus tip in nasutes
Frontal gland	frontal gland	One of the largest soldier glands; secretion may glue, irritate or repel enemies
Labral shape	labral shape	Tongue-shaped, bifid, asymmetric or grooved — a genus-level character
Postmentum	postmentum	Elongated and widened in soldiers, shaped by the head; often sculptured
Head width	head width	The most-used soldier measurement; compared with pronotal width to separate families

6. Internal organs

The gut has three regions. The foregut comprises the mouth, pharynx, esophagus, crop and proventriculus (gizzard): its chitinous lining bears longitudinal ridges, each with transverse rows of palmate processes carrying 8–10 spines pointing backwards to prevent regurgitation; behind it lies the stomodeal valve. The midgut runs from the stomodeal valve to the Malpighian tubules, lined by columnar and regenerative cells with a brush border, and is enclosed by the peritrophic membrane, a protein mesh that protects the epithelium and acts as an ultrafilter. The hindgut runs from the Malpighian tubules to the anus; its anterior part dilates into the gourd-shaped paunch, thin-walled and housing symbiotic flagellates and bacteria, followed by the colon and rectum with six parallel rectal pads.

In Termitidae the hindgut is further modified: Malpighian tubules are fewer, the proventriculus simplified, midgut caeca lost, and a mixed segment of mid- and hindgut epithelium appears between midgut and P1, with the Malpighian tubules clustered nearby as a Malpighian knot; a sclerotised enteric valve forms between P1 and P3. Hindgut compartments follow Holmgren (1909): the enteric valve is P2, P1 (ileum) precedes it, and P3 (paunch), P4 (colon) and P5 (rectum) follow. In lower termites P3 is the largest compartment and is packed with flagellates; Termitidae lack hindgut flagellates and rely on bacteria; Macrotermitinae and some relatives also cultivate fungus combs.

Other internal organs include the brain (proto-, deuto- and tritocerebrum) with the subesophageal ganglion, three thoracic and six abdominal ganglia forming the ventral nerve cord; paired ovaries of many ovarioles (from 7–10 per side in Kalotermitidae to several thousand in Macrotermes), oviducts, spermatheca and vagina; paired testes, vasa deferentia, ejaculatory duct, seminal vesicles and accessory glands; and the frontal, salivary (labial), mandibular, sternal and tergal glands.

Name	Latin / English	Notes
Alimentary canal	alimentary canal	Fore-, mid- and hindgut; regional anatomy is used at subfamily level
Foregut	foregut (stomodaeum)	Mouth to stomodeal valve, chitin-lined
Pharynx	pharynx	Dilated tube behind the mouth, flanked by salivary glands
Esophagus	esophagus	Narrow tube from pharynx to proventriculus
Crop	crop	Storage region of the foregut, often synonymous with “stomach”
Proventriculus (gizzard)	proventriculus (gizzard)	Ridged, with palmate processes and spines; its armature is taxonomically useful
Stomodeal valve	stomodeal valve	Valve at the foregut–midgut junction
Midgut	midgut (mesenteron)	Stomodeal valve to Malpighian tubules; peritrophic membrane and brush border
Midgut caeca	midgut caeca	Pouches at the anterior midgut; usually lost in Termitidae
Peritrophic membrane	peritrophic membrane	Protein mesh around the food bolus; protection and ultrafiltration
Malpighian tubules	Malpighian tubules	Excretory organs opening at the midgut–hindgut junction
Malpighian knot	Malpighian knot	Cluster of tubules near the mixed segment in some Termitidae
Mixed segment	mixed segment	Segment with both mid- and hindgut epithelium; unique to Termitidae
Hindgut	hindgut (proctodaeum)	Malpighian tubules to anus
P1 (ileum)	ileum (P1)	Hindgut compartment before the enteric valve
Enteric valve	enteric valve (P2)	Sclerotised valve; its spines and ridges are used in classification
P3 (paunch)	paunch (P3)	Dilated hindgut compartment; holds flagellates in lower termites
P3 diverticulum	P3 diverticulum	Side pouch of P3 in some groups (e.g. Cubitermes)
P4 (colon)	colon (P4)	Narrower middle hindgut
P5 (rectum)	rectum (P5)	Terminal hindgut with rectal pads
Rectal pads	rectal pads	Six parallel longitudinal folds; water and ion recovery
Hindgut flagellates	hindgut flagellates	Cellulose-digesting protists in lower termites
Salivary (labial) gland	salivary (labial) gland	Beside the pharynx, opening into the mouth; enzymes and binding agents
Mandibular gland	mandibular gland	At the mandible base; digestion and chemical communication
Ovary	ovary	Paired, made of ovarioles whose number varies greatly
Ovariole	ovariole	Egg-producing unit; 7–10 per side in Kalotermitidae, 30–79 in Reticulitermes, 100–200 in Coptotermes, thousands in Macrotermes
Oviduct	oviduct	Lateral and median ducts carrying eggs
Spermatheca	spermatheca	Sperm-storage sac dorsal to the vagina
Vagina	vagina	Chamber before the female gonopore
Testis	testis	Paired, of testicular tubules and follicles
Vas deferens	vas deferens	Duct carrying sperm to the ejaculatory duct
Ejaculatory duct	ejaculatory duct	Duct before the male gonopore; accessory glands lie dorsally
Seminal vesicle	seminal vesicle	Dilated part of the ejaculatory duct storing sperm
Accessory gland	accessory gland	Male reproductive gland; about 2.5 mm long in mature kings
Brain	brain	Proto-, deuto- and tritocerebrum; deformed by the huge frontal gland in nasutes
Subesophageal ganglion	subesophageal ganglion	Supplies the mandibles, maxillae, labium and hypopharynx
Ventral nerve cord	ventral nerve cord	Three thoracic and six abdominal ganglia; the last is fused from ganglia 7–11

7. Using these terms with descriptions and keys

Family and genus pages now carry morphological descriptions instead of keys; species pages carry one where it has been compiled, and otherwise the original description citation with a link to the genus page. Only the checklist (order and Termitidae subfamily) and the Kalotermitidae page (world genera) retain keys. Before using one, check three things: which caste you have, whether the specimen is complete (wings, antennae, tarsi and palps break off easily), and whether measurements follow the same standard. The features below most often open a couplet; they are ordered from easiest to hardest.

1. Count the tarsomeres — 4 in most families; 5 in Mastotermitidae; 5 ventrally and 4 dorsally in Archotermopsidae; 3 in Stylotermes and Indotermes.
2. Check the tibial spur formula — 3:3:3, 3:2:2, 2:2:2 …, counted on all three legs.
3. Look for the fontanelle — present in Neoisoptera (Rhinotermitidae, Termitidae and allies), usually absent in lower termites; at the nasus tip in nasutes.
4. Check the ocelli — one pair, in reproductives only; do not mistake a pigment patch of a reduced compound eye for an ocellus.
5. Measure the mandibles — left mandibular index and tooth counts are standard at genus and species level; soldiers are often asymmetric.
6. Count cercal segments — usually 2; 5–8 in Mastotermitidae and some primitive taxa.
7. Compare wing scales — forewing scale much larger than hindwing scale (Kalotermitidae, Rhinotermitidae) or about equal (Termitidae).
8. Check venation — whether R and Rs are fused, whether an anal vein is present, where M arises and branches; the hindwing anal lobe is large only in Mastotermitidae.
9. Soldier head and pronotum — head shape (square, pear-shaped, conical) and pronotal width relative to head width are the entry points for family and genus keys.
10. Dissect the gut (subfamily level) — presence and position of the mixed segment, Malpighian tubule insertion and knot, P3 diverticulum, enteric valve structure.

For finer identification, enter the checklist and open the family or genus page; every description and every retained key cites its source, and any term can be looked up here by Chinese or Latin name.

8. Names, synonyms and sources

The same structure often carries different names in different literatures; when reading a key, trust the Latin/English term. Common correspondences:

• Postmentum / gula — Chinese works use 后颏; older English works often write gula, although the two are not strictly homologous. Compare by position: the large plate at the base of the labium.
• Vertex / 头盖 — Chinese textbooks call the region behind the transverse line 头盖; English usually says vertex.
• Proventriculus / gizzard — the same organ; the first is morphological, the second functional (also “gizzard” in Chinese 砂囊).
• Enteric valve / P2 — P2 is the compartment number, enteric valve the morphological name.
• Arolium / 爪间突 — the pad between the claws in some Kalotermitidae.
• Fontanelle / frontal pore — the same opening; the second stresses that it is the duct of the frontal gland.

Entries are compiled from the sources below; the wording is the site’s own and does not reproduce the original figures. For figure numbers, measurement ranges and locality records, consult the originals:

• Huang Fusheng, Song Shihan, Zhu Shimuo et al. (2000) Fauna Sinica, Insecta Vol. 17, Isoptera. Science Press, Beijing.
• Cheng Dongbao & Yang Zhaofen (2014) Termitology. Science Press, Beijing.
• Krishna K., Grimaldi D. A., Krishna V., Engel M. S. (2013) Treatise on the Isoptera of the World. Bulletin of the American Museum of Natural History 377.
• Biology of Termites: A Modern Synthesis (Chinese translation).

This page covers morphology only. How castes arise, how nests are built and how termites feed are treated in the [biology page](https://termite-extant-isoptera.org/en/basics/biology/). Corrections of terms or typographical errors are welcome on the guestbook.