~The Black-Rat Blister-Beetle~, (_Lytta murina_, Le Conte.)--This species (Fig. 8,) is entirely black. There is a very similar species, the black blister-beetle, (_Lytta atrata_, Fabr.,) from which the black-rat blister-beetle is distinguishable only by having four raised lines placed lengthwise upon each wing-case, and by the two first joints of the antennae being greatly dilated and lengthened in the males, of the lath species. It is asserted by some authors that the black blister-beetle is injurious to the potato; but I can not see how it could do much damage to that crop, as the perfect insect does not appear until late in August, when the potato crop is nearly out of its reach. Not so, however, with the black-rat blister-beetle, which is on hand ready for business early in the season. This insect does considerable damage to the potato in Iowa, and neighboring States; it is also found, though in not so great numbers, throughout the whole of the Northern States. ~The Margined Blister-Beetle~, (_Lytta marginata_, Fabr.)--This species (Fig. 9) maybe at once recognized by its general black color, and the ash-gray edging to its wing-cases. It usually feeds on certain wild plants, but does not object to a diet of potato-leaves. Though found over a large extent of country, it seldom appears in numbers large enough to damage the potato crop materially. Like other blister-beetles, it goes under ground to pass into the pupa state, and attacks the potato only when it is in the perfect or winged state. ~The Three-Lined Leaf-Beetle~, (_Lema trilineata_, Olivier.) The larva of the three-lined leaf-beetle may be distinguished from all other insects which prey upon the potato by its habit of covering itself with its own excrement. In Figure 10, _a_, this larva is shown in profile, both full and half grown, covered with the soft, greenish excrementitious matter which from time to time it discharges. Figure 10, _c_, gives a somewhat magnified view of the pupa, and Figure 10, _b_, shows the last few joints of the abdomen of the larva, magnified and viewed from above. The vent of the larva, as will be seen from this last figure, is situated on the upper surface of the last joint, so that its excrement naturally falls upon its back, and by successive discharges is crowded forward toward its head, till the whole upper surface is covered with it. There are several other larva, feeding upon other plants, which wear cloaks of this strange material. Many authors suppose that the object of the larva in all these cases is to protect itself from the heat of the sun. In all probability the real aim of nature in the case of all these larvae is to defend them from the attacks of birds and of cannibal and parasitic insects. There are two broods of this insect every year. The first brood of larvae may be found on the potato-vine toward the latter end of June, and the second in August.