The grain Aphis, in certain years, desolates our wheat fields. We have seen the heads black with these terrible pests. They pierce the grain, extract the sap, causing it to shrink and lose the greater part of its bulk. It is a most insidious and difficult foe to overcome. [Illustration: 258. Leaf-hopper of the Vine.] The various leaf-hoppers, Tettigonia (Fig. 258) and Ceresa, abound on the leaves of plants, sadly blighting them; and the Tettigonias frequent damp, wet, swampy places. A very abundant species on grass produces what is called "frog's spittle." It can easily be traced through all its changes by frequently examining the mass of froth which surrounds it. Tettigonia Vitis blights the leaf of the grape-vine. It is a tenth of an inch long, and is straw-yellow, striped with red. Tettigonia rosae, a still smaller species, infests the rose, often to an alarming extent. The Notonecta, or water boatman, is much like a Tettigonia, but its wings are transparent on the outer half, and its legs are fringed with long hairs, being formed for swimming. It rows over the surface in pursuit of insects. Notonecta undulata Say (Fig. 259) is a common form in New England. Another insect hunter is the singular Ranatra fusca (Fig. 260). It is light brown in color, with a long respiratory tube which it raises above the surface of the water when it wishes to breathe. This species connects the Water-boatman with the Water-skaters, or Gerris, a familiar insect, of which Gerris paludum (Fig. 261) is commonly seen running over the surface of streams and pools. [Illustration: 259. Notonecta.] [Illustration: 260. Ranatra.] [Illustration: 261. Water Skater.] [Illustration: 262. Pirates.] Reduvius and its allies belong to a large family of very useful insects, as they prey largely on caterpillars and noxious insects. Such is Pirates picipes (Fig. 262), a common species. It is an ally of Reduvius personates, a valued friend to man, as in Europe it destroys the bed-bug. Its specific name is derived from its habit while immature, of concealing itself in a case of dust, the better to approach its prey. [Illustration: 263. Phymata.] Another friend of the agriculturist is the Phymata erosa (Fig. 263). Mr. F. G. Sanborn states that "these insects have been taken in great numbers upon the linden trees in the city of Boston, and were seen in the act of devouring the Aphides, which have infested the shade trees of that city for several years past. They are described by a gentleman who watched their operations with great interest, as 'stealing up to a louse, coolly seizing and tucking it under the arm, then inserting the beak and sucking it dry.' They are supposed to feed also on other vegetable-eating insects as well as the plant louse."