RASTEREIGENSCHAFTEN DES KOMPLEXAUGES VON CATAGLYPHIS BICOLOR 735 



SUMMARY 



The compound eye of the désert ant, Cataglyphis bicolor, consists of more than 

 1200 ommatidia, if one refers to the largest individuals (length of the head 

 capsule in latéral view 2.20 + 0,03 mm). The dioptrie apparatus is composed 

 of a crystalline cone (length 30.9 + 0.2 (jim) and a cuticular lens. The latter can 

 be regarded as a modified multilayered cuticule (width of the distal zone a d = 

 20. 1 + 0.2 [xm, maximum refractive index n = 1 .52) with a half-sphered cuticular 

 cone (r = 7. 1 + 0. 1 fjim) on its proximal side. 



The interommatidial inclination Ap (angle between the optical axes of adjacent 

 ommatidia) is calculated from the diameter of corneal facets and the radius 

 of curvature by means of stereoscan électron microscopic graphs and histo- 

 logical sections (K). Furthermore, it is directly measured with respect to the 

 optical axes of the cuticular lens Systems (C). Using the C-method mean values 

 of A9 (z) = 4.3 + 0.1° and A9 (x) = 3.4 ±0.1° are obtained for the trans- 

 versal (horizontal) and the x-direction in the central part of the eye. The 

 x-direction déviâtes by 30° from the longitudinal (vertical) axis. 



The visual fields (Ap) of single ommatidia in light-adapted eyes are recorded 

 by use of an angular sensitivity distribution. The sensitivity distribution, 

 approximating a Gauss-function, can be obtained by measuring the amount 

 of light passing through the dioptrie apparatus after having entered the 

 cuticular lens from varying directions in space. The half-width of that trans- 

 mission distribution was calculated as Ap (1) = 8,8° (longitudinal axis) resp. 

 Ap (t) = 6,8° (transversal axis). Thus the visual fields of adjacent ommatidia 

 strongly overlap. 



In the central région of the honeybee eye Ap is measured for comparison 

 (Ap = 2.6° in both, longitudinal and transversal direction). 



RÉSUMÉ 



Les yeux composés de la fourmi du désert Cataglyphis bicolor contiennent 

 environ 1200 ommatidies polir les individus les plus grands (longueur latérale 

 de la tête 2.20 + 0.03 mm). L'appareil dioptrique est composé d'un cône 

 cristallin (longueur b = 30.9 + 0.2 [xm, mêmes individus que plus haut) et 

 d'une lentille cuticulaire qui peut être considérée comme la cuticule à structure 

 lamellaire modifiée (largeur de la partie distale: a d = 20.1 +0.2 y.m, index de 

 réfraction maximal: n=1.52) à laquelle est ajoutée une demi-sphère 

 (r = 7. 1 + 0. 1 fxm) du côté proximal. 



