Der Kopf der Libellen: ein Organ der Gestaltung

THE HEAD OF THE DRAGONFLY, AN ORGAN OF VISUAL PRESENTATION. — In the anterior view of the head of the Zygoptera the dominant pattern is formed by contrasting cross stripes, that can also be elicited by a photoreflex. As the central part of the head protrudes foreward, this pattern is also visible in the dorsal view. It is part of a tendency to striation over the whole body, a tendencyy characterized by having differentially directed stripes following one another. In the anterior view horizontally running rings or arcs in the Zygopteran eyes increase the appearance of cross striping, but in the dorsal view they are seen to form a concentric pattern. Concentric patterns are signs that center one’s gaze, and they are part of the visual sign “eye”. — The visual sign “eye” is ancient, occuring in many animal species. In the compound eye of dragonflies and other insects it is formed by the so-called pseudo-pupils. As the dark main pseudo-pupil is always visible from any direction of viewing, a viewer’s gaze is fixed and movability of the apparent eyes is simulated. The main pseudopupils as well as the accessory pseudo-pupils represent integral features of the head, despite their changing appearance depending on the angle from which they are viewed and their variability. The same is true for the photoreflexes that form pseudo-eyes on certain parts of the head or eyes of dragonflies. — The back of the head of dragonflies is occupied by attention-attracting patterns. These include mock-eyes, which are found in certain Zygoptera and Anisoptera. — Also noted are the frontal horalets on the Libellulidae in respect of their communicative significance, as well as the occurrence of figures appearing to be oral fissures or teeth in the antero-median front aspect of the head of Zygoptera and Anisoptera. Like the visual sign “eye” they signal “head”, “front” and “danger”. Some of the patterns and signs in dragonflies and other insects which have proved successful in attracting attention and holding the view also belong to the repertoire used by man to produce particular impressions. This is illustrated by tribal masks and the pictures of expressionist painters. In tribal rites the significance of the mask is revealed in dances. Analogies are recognizable in the male mating displays and showfights of the Calopterygidae.