CHAPTER XII 

 THE INSECTIVORES ORDER INSECTIVORA 



THE absence of any vernacular name for that group of Mammals, of which the 

 shrews, moles, and hedgehogs are the best known representatives, compels us to 

 adopt an anglicized form of the Latin term by which the group is known ; and we 

 accordingly use the term Insectivores in this sense. This term, it is almost super- 

 fluous to add, refers to the insect-eating habits of most of the members of this order, 

 and it is a good one, since, with the exception of the bats, there is no other group of 

 Mammals which prey so exclusively on insects, or other small creatures. 



Most of the Insectivores are comparatively small-sized animals; and, with the 

 exception of the family of tree-shrews, and some of the aquatic forms, all are of 

 more or less purely nocturnal habits. In the absence of any very strongly-marked 

 characteristics, like the wings of the bats, the group is by no means easy of strict 

 definition, more especially when we have to avoid entering into the consideration 

 of abstruse anatomical details. 



In addition to their generally small size and nocturnal habits, the 

 Insectivores may immediately be recognized by the following structural 

 features. All their toes are furnished with claws, and are in most 

 cases five in number on each foot ; while in no instance is either the thumb or the 

 great toe capable of being opposed to the other digits. They walk either on the 

 whole, or the greater portion, of the soles of their feet ; and never on their toes only, 

 in the manner of a cat or dog. Their upper molar teeth carry a number of small 

 and sharp cusps, which are arranged either in a V-shaped or a W-shaped pattern ; 

 and their incisor teeth, of which there are not less than two pairs in the lower jaw, 

 never assume the chisel-like form found in all the Rodents (rats, porcupines, hares, 

 etc. ) ; but the first or innermost pair is very frequently larger than either of the 

 others, thereby distinguishing them from the Carnivores. In no instance is one pair 

 of the cheek-teeth in each jaw ever modified so as to act with the scissor-like action 

 characteristic of so many of the Carnivores. Then again the tusks, or canine teeth, 

 are generally not markedly distinct from the other teeth,* so that it is frequently a 

 matter of some difficulty especially in the lower jaw to decide which teeth are 

 incisors, which tusks, and which premolars. This may be readily verified by com- 

 paring the skull of a hedgehog with that of a dog, in which the tusks cannot possi- 

 bly be confused either with the incisors in front, or with the premolars behind. 



If, again, we examine the skeleton of an Insectivore, it will be found that 

 there are (with the single expection of one peculiar African species) always a pair 

 of complete collar bones, or clavicles connecting the bladebones (scapula) with the 



* This is not so in the common tenrec, which has large tusks. 

 (3*0) 



