One word more on comparative manners. The Mantis goes in for battle and cannibalism; the Empusa is peaceable and respects her kind. To what cause are these profound moral differences due, when the organic structure is the same? Perhaps to the difference of diet. Frugality, in fact, softens character, in animals as in men; gross feeding brutalizes it. The gormandizer gorged with meat and strong drink, a fruitful source of savage outbursts, could not possess the gentleness of the ascetic who dips his bread into a cup of milk. The Mantis is that gormandizer, the Empusa that ascetic. Granted. But whence does the one derive her voracious appetite, the other her temperate ways, when it would seem as though their almost identical structure ought to produce an identity of needs? These insects tell us, in their fashion, what many have already told us: that propensities and aptitudes do not depend exclusively upon anatomy; high above the physical laws that govern matter rise other laws that govern instincts. CHAPTER XI THE WHITE-FACED DECTICUS: HIS HABITS The White-faced Decticus (D. albifrons, Fabr.) stands at the head of the Grasshopper clan in my district, both as a singer and as an insect of imposing presence. He has a grey costume, a pair of powerful mandibles and a broad ivory face. Without being plentiful, he does not let himself be sought in vain. In the height of summer we find him hopping in the long grass, especially at the foot of the sunny rocks where the turpentine-tree takes root. At the end of July I start a Decticus-menagerie. As a vivarium I adopt a big wire-gauze cover standing on a bed of sifted earth. The population numbers a dozen; and both sexes are equally represented. The question of victuals perplexes me for some time. It seems as though the regulation diet ought to be a vegetable one, to judge by the Locust, who consumes any green thing. I therefore offer my captives the tastiest and tenderest garden-stuff that my enclosure holds: leaves of lettuce, chicory and corn-salad. The Dectici scarcely touch it with a contemptuous tooth. It is not the food for them. Perhaps something tough would suit their strong mandibles better. I try various Graminaceæ, including the glaucous panic-grass, the miauco of the Provençal peasant, the Setaria glauca of the botanists, a weed that infests the fields after the harvest. The panic-grass is accepted by the hungry ones, but it is not the leaves that they devour: they attack only the ears, of which they crunch the still tender seeds with visible satisfaction. The food is found, at least for the time being. We shall see later.