1. Providing the nest with vegetable food,Lethrus performs repeated excursions of about l m from the hole and returns home. 2. Homing by the straight line,Lethrus walks in compass direction toward the nest; the distance traveled is equal to the estimated distance to the hole, and in a case of faultLethrus begins the circling search.Lethrus is able to integrate over the complex path. 3. Lethrus sets direction relative to celestial cues: the sun and the polarized skylight. 4. Lethrus has two photoreceptor systems: the green-sensitive and UV-sensitive one; only an ultraviolet polarization pattern is used for polarotaxis. 5. The eye ofLethrus evolved from the superpositional prototype; it is adapted to diurnal vision by shortening of the clear zone and by thickening of the light-guiding tracts from the cone to the rhabdom. 6. Lethrus is different from other Lamellicorns possessing a typical multilobed rhabdom in thatLethrus has a crustacean-type rhabdom. It is assumed that this specialization of rhabdom provides the perfect analysis of polarized light and polarotaxis. 7. The complex orientational and nest behavior ofLethrus is not accompanied by enlargement of the brain and its presumed associative centres, the mushroom bodies. Among several scarabaeid beetles of comparable size (Amphimallon solstitialis, Geotrupes stercorosus)Lethrus apterus gains the first place in behavioral complexity but the last in number of sensilla on the antennal dumb, number of ommatidia, and the volume of mushroom globuli.