The isoptera or termites (Isoptera Brullé, 1832) are an order of terrestrial insects, with social organization, of small or medium size.
From a systematic point of view they belong to:
The order of termites includes about 2800 species grouped, as written, in seven Families, even if there is still no full agreement of opinions among the specialists on this classification.
Geographic Distribution and Habitat –
Isoptera are an entomological order known, at present, fossilized already in the Tertiary, which today has about 2800 species widespread especially in tropical countries thanks to the high values of humidity and temperature. In temperate regions, the few species of termites present are known above all for the damage to wood and paper materials in urbanized areas.
In Italy there are two stable plant species, Kalotermitide Kalotermes flavicollis Fabricius and Rinotermitide Reticulitermes lucifugus Rossi. Recently, due to international transport, a new termite of the Kalotermitidae family has been imported, the Cryptotermes brevis, originally from the Indio-Asiatic area. It has been located only in some Italian cities, especially in the center-south.
Morphology and Anatomy –
Termites are winged insects, meioptera or wingless, with uniform colors, pale or not very bright, and with exoskeleton usually of weak or mediocre consistency.
These insects have an amphipecyl polymorphism, with initially winged males and females fertilized and sterile males and females (workers and soldiers) always wingless, monomorphic or polymorphic.
The head is prognate or subprognate, free, quite mobile, of various shapes and sizes depending on the species and / or castes; in some cases (“nasuti soldiers”) it is prolonged dorsally and anteriorly in a sort of tubule at the apex of which the duct of the frontal gland opens, frequently provided with a variously developed epicranial sulcus.
They have eyes and 2 ocelli, or missing.
The antennae are of modest length, moniliform, composed of a number of antennomers between 9 and 32.
The mouthparts are chewing. The labrum is developed, but very variable in shape and sometimes very elongated.
The mandibles are robust, of various shapes and sizes, sometimes (in soldiers) enormous, monstrous or asymmetrical, sometimes very small or subatrophic. Jaws with distinct lobes, galea often bisegmented, lacinia sclerified and distally provided with spiny formations, 5-articulated palps. Labium with submental and chin fused together and with prement provided with glosses, paraglosses and 3-articulated palps. Neck with cervical sclerites.
The chest is depressed and with wide notes. Free prothorax and sometimes larger than the following segments; the latter are similar to each other.
The ambulatory legs are similar to each other, with large and close coxes, tarsi commonly of 4 articles, rarely 5-articulated or imperfectly 5-articulated, pretended with 2 nails and provided, or not, with arolium.
They have large, membranous, subequal wings (hence the name), with primitive or reduced venulation, and without transverse ribs (the latter often replaced by a very fine and irregular reticulum); with the exception of the Mastodermatids, the wings subproximally have a preformed transverse line of rupture (called “humeral sulcus”), along which they will break after the pre-nuptial flight, leaving the so-called “humeral scale” attached to the thorax.
The abdomen is sessile, composed of 10 urites, with the XI urotergus fused with the X, and the XI urosterno reduced and represented by a pair of paraprocts. VII urosterno very large in the female, in which it completely or partially covers the VIII and IX. IX urosterno provided, or not, with styles in both sexes. Cerci 1-8 articulated.
The nervous system consists of a variously developed central apparatus, in relation to the brain and the eyes, in the reproductive and sterile caste. 3 thoracic and 6 abdominal ganglia.
The digestive system consists of a more or less convoluted alimentary canal, with stomodeo provided with ingluvie and gizzard with more or less developed armor. Mesenteron quite long and tubular and provided, in the most primitive species, with 4-5 gastric cecum. Proctodeus with colon often separated from the ileum by a valve, very dilated in the species hosting symbiotic Protozoa.
The tracheal system has 10 pairs of stigmas (2 in the chest and 8 abdominals) and anastomosed tracheas.
The circulatory system is a developed dorsal vessel and 8-10 pairs of ostioli.
The excretory system has 2-8 Malpighian tubes.
The secretory apparatus consists of the glands of the labrum, included in it, which flow into the wing vault (missing in the images and in some soldiers); mandibular glands (in Kalotermes flavicollis Fabricius according to Lambinet made up of two types of cells: large and secretory and small generating new glandular canaliculi); labial (or salivary) acinar glands, provided with reservoirs and opening into the prefharynx, particularly developed in the workers, and even enormous in the soldiers of Pseudacanthotermes Sjöst; “frontal gland”, characteristic of the order (and of the families of rhinotherms and termites), which originates from the differentiation of a group of epidermal cells in the medial-dorsal area of the head, found in all castes, but especially developed and complex in soldiers, where it sometimes assumes such dimensions as to reach the caudal end of the abdomen, opening through a pore that opens into a depressed and epigmented area called “window” or “fontanel” innervated by a fontanellar nerve coming from the cerebro, whose function is still problematic, but in some cases defensive. Sternal epidermal glands (in urosterni IV, or V, that is, in Mastotermitidi, III, IV, V); these glands are present in all castes but are involved in functional amphigonics, according to Noirot, and secrete a fermone-trace; numerous integumental glands. Retrocecebral endocrine system with posteriorly fused cardiac bodies and even allied bodies.
The reproductive system consists of a very variable number of ovaries of panostic ovaries, spermatheca and a pair of symmetrical colleteric glands, consisting of numerous tubules. Ovipositor formed by three pairs of small valves in Mastotermes Froggart and the rudiments of their first pair in other genera. Multifollicular testicles, variously developed accessory glands and more or less reduced spermatic vesicles. Gonotremia between VII-VIII urosterno. Membrane copulatory organ. The genital organs in termites are well developed almost only in amphigonic ones. In workers and soldiers they appear more or less aborted, and sometimes completely atrophied (as in Hospitalitermes monoceros Koen.).
Attitude and Life Cycle –
Societies of Isoptera are persistent and common. Queens can live up to 80 years. They are characterized by unisexual (amphipecyl) polymorphism. In these societies we distinguish two castes: the fertile or fertile caste (real) and the sterile caste (both male and female), workers and soldiers.
The fertile caste is made up of imaginal amphigonians and, often when these are lacking, neotenic amphigonians.
Imaginal amphigonic (real real): they are always winged; they have small and medium size (rarely large); the mouth apparatus is chewing; the antennae are well developed; the wings persist for a short time; the integuments are not very consistent and with light pigmentations. After the pre-nuptial flight, the royals descend to the ground and begin the construction of the first cell of the nest, inside which, after having torn off the wings and also a part of the antennae, they mate .
As a rule, there is delfogamy (the royals that mate come from the same nest), but sometimes they can also come from different nests. The female can undergo a postmetamorphic physogastry. The male stays close to the female, fertilizing her periodically. The number of eggs laid daily is very high (up to 30,000).
The reals of replacement or complement: derive from individuals initially destined to become workers or soldiers and only later induced to bring the sexual organs to maturity (they present themselves in neotenic, brachitter or apterous forms).
The sterile caste (sometimes there are no soldiers, sometimes workers who are replaced by the nymphs) is made up of:
– the soldiers are airborne and usually unable to feed themselves; they have a very large skull and strongly sclerified and pigmented walls; the jaws are very large; in some species they possess a frontal gland which secretes a viscous substance with which they defend themselves from enemies; sometimes they have a very elongated lower lip;
– the workers are very active and carry out various jobs such as the care of the royals, the removal of food supplies, the construction and expansion of nests, the cultivation of mushrooms.
Their biological cycle begins with the deposition of the eggs by the fertilized females, which hatch within a few weeks; the larvae emerge from them and begin to feed on the woody material by digging deep tunnels. This larval stage is the most harmful as it lasts a very long time and can cause significant consequences, especially because it is not detectable. At the end of the larval phase, the metamorphosis into a pupa occurs, which, after a few weeks, turns into an adult.
At this point, through the formation of surface holes (called flickering) the insect comes out to start a new life cycle.
Their reproduction occurs exponentially and therefore these insects can be extremely harmful to humans; the environmental conditions that favor their spread are warm temperatures and medium humidity.
Isoptera nests are often imposing constructions. They can be epigean, underground or dug out of wood. They can be built with earth, cemented earth, earth mixed with dung, earth mixed with saliva, wood mixed with saliva or other.
Inside the nests there are particular conditions: high humidity, high temperature and complete darkness. To exit the nest, openings are made (at night or in the twilight hours) or covered paths are built. Often there are mushroom crops that are used as food. New societies are founded by swarming, offshoot or sociotomy.
Ecological Role –
The dietary regime of the Isoptera is essentially herbivorous. These insects feed mainly on cellulose which they derive from various substances: wood of living plants, dry, rotten, infiltrated by colonies of bacteria or fungal mycelia, leaves, stems, seeds, fungi, lichens, artifacts (paper, cardboard, cotton wool, cotton fabrics, etc.). In addition to cellulose, their diet includes processed foods (stomodeal and proctodeal), animal substances (tearmite eggs themselves, exuviae, dead, sick or injured bodies, or living bodies of community mates, symbiotic protozoa). There are, again, some heterophagous species, such as the Mastotermes darwiniensis Froggart (which, in this regard, recalls its affinity with the Blattodei), which attack sugar, leather, horn, ivory, wool, etc. Stomodeal food is represented both by an opalescent and viscous liquid (which looks like saliva), and by a substance including regurgitated woody fragments. The proctodeal food consists of a fluid coming from the colon and containing symbiont protozoa. The actual droppings, on the other hand, pasty or liquid, are used to close cracks or to form a cement that is used to build small partitions, to pack a sort of cardboard, to spread the walls of the nest, etc. The proctodeal food is solicited by the applicants with various maneuvers and particularly with the antennae, and its exchange among the members of society (trophylaxis) is extremely intense. Processed foods are the only nourishment for various castes, or stages, of society.
In order to supply themselves with food, the warriors, who are lucìfugas, frequently abandon their shelters and undertake expeditions sometimes along underground tunnels, sometimes externally, but protecting themselves with tubular covers of earth or chewed wood or mixed dung, which allow them to walk and work. protected from light, from enemies and in conditions of suitable humidity; finally, sometimes in the open air, under the supervision of the soldiers and usually choosing antelucane or nocturnal hours, or even cloudy and humid days. There are Thermites who stockpile plant supplies, and even those who amass hundreds of dead and withered bodies of their companions.
Termites are therefore xylophagous organisms (that is, they eat wood); their ecological importance depends on the fact that the equivalent of one third of all the matter produced each year by plants is devoured by them. In a terrestrial ecosystem, the production of living matter is almost uninterrupted, and if it were not demolished with a speed correlated to that with which it is formed, after a short time the system would enter into crisis, because there would be no space for the new ones. organisms and materials to continue production. The destruction of the wood, of the other vegetal parts and of the other organic residues, ensures the release of nutrients in the soil which, in this way, becomes fertile.
With their robust jaws they crush the woody mass and feed on it; furthermore, the food is distributed among the individuals of the colony by mouth-to-mouth regurgitation (oro-oral trophylaxis), or also by oral-anal trophylaxis.
With trophylaxis, termites also pass protozoa and symbiont bacteria. Bacteria are useful for the digestion of cellulose, which they transform into lipids. Very often they are housed in protozoa which, in exchange for lipid nutrients, provide them with a suitable environment and other metabolic products.
Only a small part of the protozoa is digested by termites, as a protein food to make up for the lack of protein in the wood. There is, therefore, a cooperation between the populations of bacteria and protozoa, in which the bacteria can actively penetrate, a cooperation between the termite and the community of microorganisms living in its intestine. This cooperation leads the biocenosis back to the biotope and closes the trophic chain of ecosystems inhabited by termites.
The termite mounds are also frequented by small animals, mostly hexapods (Collembola, Coleoptera, etc.), strongly adapted to the associative life with the Tearmites, which show a great appreciation for the special substances they produce. The morpho-physiological evolution of these hosts, defined as termitophiles, has developed parallel to that of the same Thermites.
For termite prevention, special attention should be paid when:
– there are outbreaks already present;
– there are large quantities of wood;
– there are nearby plants, especially if they are sick, dead or damaged;
– there is a lot of humidity in the environment and in the premises;
– there are beams embedded in the wall (not insulated);
– there are structures attached to the walls;
– there are areas where condensation forms;
– there is little light;
– there is little air.
For these reasons it is strongly recommended to insulate the heads of the beams with special niches made of pressed bricks to avoid accumulation of humidity, to separate the beams from the wall with 0.5 cm of vacuum to let the air pass or filled with insulation. In libraries it is necessary to ventilate the rooms, isolate cabinets and shelves and even the books from the shelves (due to the accumulation of humidity) with an annual handling of the entire archive.
For the defense against termites we recommend the use of chemical means such as permethrin mixed with water to be distributed on the nests (when they are found) but they are often not definitive. The use of growth regulators such as hexaflumuron, which stops moulting, seems to be successful; it is given with food baits and brought into the nest by the workers, then with the trophylaxis they infect each other reaching the queen. For the furniture (which can still be saved), heating up to 53 ° C or controlled atmosphere is used for long periods.
– Wikipedia, the free encyclopedia.
– Russo G., 1976. Agricultural Entomology. Special Part. Liguori Editore, Naples.
– Pollini A., 2002. Manual of applied entomology. Edagricole, Bologna.
– Tremblay E., 1997. Applied entomology. Liguori Editore, Naples.