Collembola (Spring-tails)
Mouthparts entognathous, principally adapted for biting; antennae usually 4-segmented, the first 3 segments with intrinsic muscles; compound eyes absent. Abdomen 6-segmented, usually with three pairs of appendages, i.e. a ventral tube on segment I, a minu
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COLLEMBOLA (Spring-tails) Mouthparts entognathous, principally adapted for biting; antennae usually 4segmented, the first 3 segments with intrinsic muscles; compound eyes absent. Abdomen 6-segmented, usually with three pairs ofappendages, i.e. a ventral tube on segment I, a minute retinaculum on III, and a forked springing organ on IV. A tracheal system is usually absent and there are no Malpighian tubules. Metamorphosis slight. Collembola are small insects rarely exceeding 5 mm in length, and occurring in almost all situations (Schaller, 1970; Paclt, 1956; Christiansen, 1964; Butcher et a/., 1971). They are found in the soil, in decaying vegetable matter, among herbage, and under bark of trees. A few species frequent the nests of ants and termites, others occur on the surface of fresh water and several are littoral or marine: Anurida maritima, for example, is daily submerged by each tide. Cavernicolous species have evolved a characteristic facies by convergence (Christiansen, 1961, 1965). The only condition which seems essential for their welfare is a certain amount of moisture, for they are rare in very dry situations. Various works on their biology, especially of the soil-inhabiting species, are among those listed on pp. 471-5. The order is world-wide and is remarkable for the extensive distribution of many of its genera and species (Salmon, 1949). Collembola vary very much in coloration. Many are of a uniform dull blue-black, as in Anurida; others are green or yellowish with irregular patches of a darker colour; a few species are banded, some are all white, one or two are bright red while metallic forms are not infrequent. In habits they are saprophagous or phytophagous, pollen grains and fungal spores or mycelium often being eaten (MacNamara, 1924; Poole, 1959). External Anatomy (Figs. 219-222)- In most species the body is clothed with hairs but some genera, notably Tomocerus and Lepidocyrtus, are scaled (Maiwald, 1972). The hairs vary in shape, often on different regions of the body; they may be simple and tapering, clavate, flattened and partially resembling scales, or plumose. The head (Denis, 1928; Bruckmoser, 1965) is pro- or hypognathous with the labrum distinctly marked off and sometimes also the clypeus and frons. The cephalic endoskeleton is not fully understood. Manton (1972) describes anterior and posterior tentorial arms and transverse segmental 'tendons' between the mandibles and maxillae, but O. W. Richards et al., Imms’ General Textbook of Entomology © O. W. Richards and R. G. Davies 1977
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GENERAL TEXTBOOK OF ENTOMOLOGY
others have denied that the cephalic apodemes constitute a true tentorium (Denis, 1928; Fran~Yois, 1972). The antennae vary greatly in length and the distal segments may be secondarily annulated. They are typically 4segmented; the maximum number of six is found in Orchesella. In the Neelidae the antennae may be shorter than the head, while in some of the Entomobryidae they are longer than the whole body. Sensory organs of varied types are usually present on the last two se
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