FIG. 257.—Head of another Carabid, with the brain and eyes normal: _op_, optic ganglion; _pcl_, brain. ] In certain cave insects where the eyes are wanting, the optic ganglia are also absent. In the eyeless cave species of Anophthalmus the optic ganglia and nerves are entirely atrophied, as they are in Adelops, which, however, has vestiges of the facets (ommatidia). Fig. 257 represents the brain of _Chlænius pennsylvanicus_, a Carabid beetle, with its eyes and optic ganglia (_op_) which may be compared with Anopthalmus, in which these parts are totally atrophied. Dujardin claimed that the degree of complication of the stalked body of the Hymenoptera was in direct relation with their mental powers. This has been proved by Forel, who has shown that in the honey bee and ants the mushroom bodies are much more developed in the workers than in the males or females and Viallanes adds that these bodies are almost rudimentary in the dragon-flies, whose eyes are so large; while on the contrary in the blind ants (Typhlopone), these bodies are as perfect and voluminous as in the ants with eyes. [Illustration: FIG. 258.—Diagrammatic outlines of sections of the upper part of the brain of a cockroach. Only one side of the brain is here represented. The numbers indicate the position in the series of 34 sections into which this brain was cut. _mb_, mushroom bodies, with their cellular covering (_c_) and their stems (_st_); _a_, anterior nervous mass; _m_, median nervous mass.—After Newton. ] Within the limits of the same order the stalked bodies are most perfect in the most intelligent forms. Thus in the Orthoptera, says Viallanes, the Blattæ, Forficulæ, and the crickets, the mushroom bodies are more perfect than in the locusts, which have simpler herbivorous habits. This perfection of the mushroom bodies is seen not only in the increase in size, but also in the complication of its structures. Thus in the groups with lower instincts (Tabanus, Æschna) the stalk does not end in a calyx projecting from the surface of the brain, but its end, simply truncated, is indicated externally only by an accumulation of the ganglionic nuclei which cover it.[43] In types which Viallanes regards as more advanced, _i.e._ Œdipoda and Melanoplus, the end of the stalk projects and is folded into a calyx. The brain of the cockroach (Periplaneta, Fig. 258) is a step higher than that of the locusts, each calyx being divided into two adjacent calices, although the cockroaches are an older and more generalized type than locusts. The stalked bodies of cockroaches are thus complex, like those of the higher Hymenoptera, the calices in Xylocopa, Bombus, and Apis being double and so large as to cover almost the entire surface of the brain.