Insectivora


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Insectivora

An order of placental mammals including shrews, moles, and hedgehogs. The tree shrews (Tupaiidae) and elephant shrews (Macroscelididae) are now recognized as unrelated, and they are placed in separate orders (Scandentia and Macroscelidea). Formerly thought to be the basal placental order, from which other orders were derived, the Insectivora is now restricted to members of the former suborder Lipotyphla. It evolved side by side with the other placental orders, with a fossil record going back to the Paleocene. A number of fossil families from the Cretaceous and early Tertiary, formerly included in the Insectivora, are classified as Proteutheria.

Living lipotyphlous insectivores are small animals: the largest (Potamogale) weighs about 1 kg (2 lb). Most eat insects, worms, and other invertebrates, for which they search in ground litter and vegetation, using their highly developed olfactory sense and their mobile, sensitive snouts. Some burrow, such as moles; some are aquatic, such as the desman. Anatomically, they are distinguished by the absense of a cecum on the intestine, reduction of the pubic symphysis (fibrocartilaginous union of bones), and characters of the skull. The cheek teeth typically have sharp cusps and crests, and the incisors are often enlarged to act as forceps. Insectivores are found on all continents except Australia and Antarctica, but only one genus (Cryptotis, a shrew) has reached South America.

Three suborders can be distinguished: Erinaceomorpha, Soricomorpha, and Chrysochloromorpha. Living erinaceomorphs belong to the family Erinaceidae, comprising the spiny hedgehogs (Erinaceinae) of Eurasia and Africa and the hairy moonrats (Echinosoricinae) of Southeast Asia.

Four living families are included in the Soricomorpha: Soricidae (shrews), Talpidae (moles, desman), Tenrecidae (Madagascan tenrecs and African otter shrews), and Solenodontidae (Solenodon, confined to Cuba and Hispaniola). Among the talpids, the subfamily Talpinae is the most advanced in modification of the forelimbs for burrowing, the Desmaninae have aquatic adaptations, and the Uropsilinae (represented by the Chinese shrew mole) retained shrewlike limbs. True moles did not reach North America until the Miocene; they were preceded in the Oligocene by the Proscalopidae, which burrowed in a different way, with the hands moving longitudinally beneath the body, instead of laterally as in true moles. The living Solenodon, in the West Indies, is one of the largest insectivores, but nevertheless shrewlike. The Tenrecidae are far removed geographically from other soricomorphs. They probably evolved in Africa, where their fossil history goes back to the early Miocene, and the otter shrews (Potamogalinae) survive on the continent of Africa today. The remainder are in Madagascar where, like the lemurs, they have evolved in diverse directions during a long time of isolation. In some ways, for example brain size, they have remained more primitive than other insectivores.

The golden moles (Chrysochloridae) are put into a separate suborder, Chrysochloromorpha. They are highly specialized burrowers, using large claws on the forefoot. They are confined to Africa, where fossils show that they were already specialized in the early Miocene. See Mammalia

Insectivora

 

an order of mammals. The body length ranges from 3 cm (the shrew Sorex minutissimus and the musk shrew Crocidura suaveolens) to 39 cm (tenrec). The head is elongated and usually ends in a movable snout. The eyes are small and, in some species, are concealed under the skin. Some insectivores (moles, desmans, shrews) have a coat of short thick fur; others are covered with bristles (tenrecs) or spines (hedgehogs). The coloration is monochromatic—gray, brown, or black; rarely is it spotted. The limbs are short and five-toed. Most insectivores are fully or partially plantigrade; some leaping species are digitigrade. The tail of some species, such as the hedgehog, is very short; in other species, for example, the desman (Desmana moschala), the tail is nearly equal in length to the body. Insectivores have well-defined cutaneous glands, which in some species exude a musky secretion. The olfactory organs of the brain are well developed; the cerebral hemispheres are small and often do not cover the cerebellum. The best-developed sense organs are those of smell and touch.

The order Insectivora comprises the following nine families: Solenodontidae, Centetidae, Potamogalidae (including the otter shrew), Chrysochloridae, Erinaceidae, Macroscelididae, Soricidae, Talpidae, and Desmanidae (the sole species being the desman). The families include approximately 63 genera, with more than 300 species. Sometimes the family Tupaiidae is included in the Insectivora.

Insectivores are found throughout the world except in Greenland, Antarctica, Australia, and most of South America. Four families—Erinaceidae, Soricidae, Talpidae, and Desmanidae—are found in the USSR. They comprise ten genera, with 38 species. Insectivores are found everywhere, as far north as the shores of the Arctic Ocean and its offshore islands; they are found in the mountains up to the snow line. There are above-ground (hedgehogs, tenrecs, shrews), subterranean (golden moles, true moles), and semiaquatic and aquatic (otter shrews, water shrews, and desmans) species.

Insectivores are primarily nocturnal animals. They are omnivorous but prefer animal substances: invertebrates and small vertebrates. For refuge, many species dig burrows, which are frequently extremely complex; small aboveground species in forests live in the litter. Insectivores are active year-round except for a few species of the family Erinaceidae that hibernate. They produce up to three litters annually, each of which contains from one to 25 young.

A number of insectivores are hunted for their fur (desmans and moles). These mammals destroy harmful insects, but they also serve as intermediate hosts of ticks carrying dangerous diseases. The numbers of some species, such as the solenodons and desmans, are very low; they are now protected species.

The Insectivora have been known since the Lower Cretaceous. They are the most ancient and primitive group of placental mammals and gave rise to many orders of mammals, including Chiroptera, Primates, Rodentia, and Carnivora. Some classification systems divide the order Insectivora into three orders.

REFERENCES

Mlekopitaiushchie fauny SSSR, part 1. Moscow-Leningrad, 1963.
Zhizn’zhivotnykh, vol. 6. Moscow, 1971.

O. L. ROSSOLIMO

Insectivora

[in‚sek′tiv·ə·rə]
(vertebrate zoology)
An order of mammals including hedgehogs, shrews, moles, and other forms, most of which have spines.
References in periodicals archive ?
1976 [a] 1993-1994, 1998 Dideiphimorphia Didelphidae Dideiphis virginiania * 15 Insectivora Soricidae Blarina brevicauda * 16 Sorex cinereus 16 Talpidne Scalopus aquaticus numerous [b] Chiroptera Vespertilionidae Myotis septentrionalis 15 Lasiurus borealis 10 Myotis sodalis 4 Pipistrellus subflavus 4 Eptesicus fuscus 4 Myotis lucifugus Lasionycteris noctivagans Lasiurus cinereus Rodentia Muridne: Sigmodontinae Peromyscus leucopus * 171 Peromyscus maniculatus 86 Reithrodontomys megalotis 16 Muridne: Arvicolinae Microtus ochrogaster * 157 Synaptomys cooperi * 27 Microtus pennsylvanicus * 12 Ondatra zibethicus * 2 Muridne: Murinae Mus musculus * 8 Dipodidne Zapus hudsonius 8 PRC Env.