164 of both sexes). Immature stages of all castes may also be present in the colony along with

(occasionally) intercastes. As the castes are of different form, it is appropriate to describe them separately.

Reproductive. The body of primary reproductives (king and queen) is normally well sclerotized; however, in physogastric queens, that is, females whose abdomen becomes enormously swollen through hypertrophy of the ovaries and consequent stretching of the intersegmental membranes (Figure 7.11C), the abdomen is pale, and the original tergal and sternal plates are the only areas of sclerotization. The head is round or oval and carries well-developed compound eyes, moniliform antennae with a varied number of segments (generally fewer in more advanced termites), and mandibulate mouthparts. In Termitidae and Rhinotermitidae a small pore, the fontanelle, occurs in the midline between or behind the compound eyes. This marks the opening of the frontal gland. In the thorax the pronotum is distinctive; the thoracic sterna are membranous. Except in Mastotermes, the two pairs of wings are very similar in appearance, with strongly sclerotized veins in the anterior portion and a basal (humeral) suture along which fracture of the wing occurs. In Mastotermes the wings have a primitive venation; also, the hindwings have alarge anal lobe as in cockroaches but lack a basal suture, though a line of weakness occurs to facilitate wing shedding. The legs are all very similar, having large coxae and four- (very rarely three-)segmented tarsi; in Mastotermes the tarsi are five-segmented. Ten obvious abdominal segments occur with the 11th tergum having fused with the 10th, and the 11th sternum being represented by the paraprocts. Except in Hodotermitidae, in females the seventh sternum forms a large subgenital plate that obscures the remaining sterna. Short cerci are present that are three-to eight-segmented in lower termites but are reduced to an unsegmented or two-segmented tubercle in higher forms. External genitalia are absent except in Mastotermes where females have a blattoid-type ovipositor and males a copulatory organ.

In neotenics (also called secondary, supplementary, and replacement reproductives) the body is less sclerotized than that of the primaries. The compound eyes are usually reduced. Neotenics may have wing buds or be wingless, their wings having been chewed off by workers. In some species female neotenics may become physogastric.

Soldier. Members of this caste are readily recognized by their large, well-sclerotized head that in some species may exceed the rest of the body in size. Though soldiers may be of either sex, the proportion of male to female individuals in this caste may vary. Primitively the mandibles are very large, sometimes enormous, and suited for biting. In other species in which the mandibles are large they may serve as pincers, or they may be asymmetrical and hinged so as to snap closed at great speed, thus delivering a powerful blow to an adversary. In Nasutitermitinae (Figure 7.12) the frons is enlarged to form a more or less pointed rostrum, at the tip of which opens the frontal gland, and the mandibles are reduced or vestigial. A large frontal gland occurs in both Rhinotermitidae and Termitidae, sometimes (in rhinotermitids) occupying most of the abdomen. The secretion of the gland may be toxic, repellent, or sticky; it is usually smeared on intruders but in some termites it can be ejected some distance. In some Kalotermitidae the head is phragmotic, that is, has a thick, sometimes sculptured frons designed to plug access holes to the nest and prevent entry of invaders. Generally soldiers are apterous though in Kalotermitidae and Termitidae they may develop from juveniles with wing buds.

Worker. In most species the body of workers is generally pale and weakly sclerotized. The head resembles that of a primary reproductive, except that the compound eyes are reduced or absent and the mandibles more powerful. Workers may be polymorphic according to their age and sex.

Except for the gut, which is modified with their mode of life (and of great use taxonom-ically), the internal structure of termites is generalized. The esophagus is a long, narrow tube and is followed by a scarcely differentiated crop. The gizzard wall is greatly folded longitudinally, each fold having cuticular thickenings and, often, teeth. The midgut is typically a short tube of uniform diameter though in physogastric queens it may be enormously enlarged, a development presumably associated with absorption of the large quantities of saliva fed to them by workers. Mesenteric ceca may or may not be present. The hindgut is well developed and differentiated into a number of regions, the most prominent of which is the large paunch containing bacterial or protozoan symbionts. The posterior wall of the paunch contains columnar epithelium and is probably a region of absorption. In lower termites (except Mastotermes with up to 15) 8 Malpighian tubules enter the gut at the junction of the midgut and hindgut; in Termitidae only 4 tubules occur. The central nervous system is orthopteroid, with three thoracic and six abdominal ganglia. In reproductive males each testis comprises up to 10 fingerlike follicles that enter the paired vasa deferentia. At the junction of the vasa deferentia and ejaculatory duct there is a pair of seminal vesicles. In reproductive females each ovary initially contains only a few panoistic ovarioles and this number remains in lower termites. However, in physogastric reproductives the number increases with maturity, reaching several thousand in some species. The paired oviducts enter the short common oviduct, which leads into the genital chamber. A spermatheca and accessory glands also enter this chamber. The reproductive organs are atrophied in workers and soldiers.

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