The various species of rapacious animals are disappearing, together with the colonies of marmots; the insectivores are also becoming scarce in consequence of the destruction of insects; while vermin, such as the suslik, or pouched marmot (Spermophilus), and the destructive insects which are a scourge to agriculture, become a real plague.
These lead on to the sousliks, Spermophilus (or Citellus), in which the incisors (as in the following genera) differ from those of all the squirrels in not being compressed.
The species, Spermophilus (or Citillus) citillus, is rather smaller than an ordinary squirrel, with minute ears, and the tail reduced to a stump of less than an inch in length.
The so-called prairie-dogs, which are smaller and more slender North American rodents with small cheek-pouches, form a separate genus, Cynosnys; while the term pouched-marmots denotes the various species of souslik, Spermophilus (or Citillus), which are common to both hemispheres, and distinguished by the presence of large cheek-pouches (see RODENTIA).