In April the injurious insects in the Northern States have scarcely begun their work of destruction, as the buds do not unfold before the first of May. We give an account, however, of some of the beneficial insects which are now to be found in grass-lands and in gardens. The farmer should know his true insect friends as well as his insect foes. We introduce to our readers a large family of ground-beetles (Carabidae, from Carabus, the name of the typical genus) which prey on those insects largely injurious to crops. A study of the figures will familiarize our readers with the principal forms. They are dark-colored, brown or black, with metallic hues, and are seen in spring and throughout the summer, running in grass, or lurking under stones and sticks in damp places, whence they sally forth to hunt by night, when many vegetable-eating insects are most active. [Illustration: 219. Calosoma scrutator.] [Illustration: 220. Calosoma calidum and Larva.] The larvae are found in much the same situations as the mature beetles. They are, elongate, oblong, and rather broad, the terminal ring of the body being armed with two horny hooks, and having a single fleshy leg beneath; and are usually black in color. The larva of Calosoma (C. calidum, Fig. 220; _a_, the beetle; and Fig. 219, C. scrutator) ascends trees to feed on caterpillars, such as the Canker worm. When about to transform to the pupa state, it forms a rude cocoon in the earth. The beetle lies in wait for its prey in shallow pits excavated in pastures. We once saw it fiercely attack a May beetle (Lachnosterna fusca) nearly twice its size; it tore open the hard sides of its clumsy and helpless victim with tiger-like ferocity. Carabus (Fig. 221, C. serratus Say, and pupa of Carabus auronitens of Europe, after Westwood) is a closely allied form, with very similar habits. [Illustration: 221. Carabus and Pupa.] [Illustration: 222. Brachinus.] [Illustration: 223. Casnonia.] [Illustration: 224. Pangus.] [Illustration: 225. Agonum.] [Illustration: 226. Carabid Larva.] A much smaller form is the curious Bombardier beetle, Brachinus (Fig. 222, B. fumans), with its narrow head and heart-shaped prothorax. It is remarkable for discharging with quite an explosion from the end of its body a pungent fluid, probably as a protection against its enemies. An allied genus is Casnonia (Fig. 223, C. Pensylvanica), which has a long neck and spotted wing covers. Figure 224, Pangus caliginosus, and figure 225, Agonum cupripenne, represent two common forms. The former is black, while the latter is a pretty insect, greenish, with purplish-red wing-covers, and black legs. Figure 226, enlarged about three times, represents a singular larva found by Mr. J. H. Emerton under a stone early in spring. Dr. LeConte, to whom we sent a figure, supposes that it may possibly be a larva of Harpalus, or Pangus caliginosus. It is evidently a young Carabid. The under side is represented. _The Insects of May._