Abstract: he optical superposition images and field angle of the compound eye of Beijing firefly Phrococelia pekinensis was observed by means of optical imaging under different adaptation states. Crystalling cones could form a real superposition image at a distance of 300-350μmfrom the surface of cornea (correspond to the level of retina) under different adaptation states. A real optical superposition image was formed by dark-adapted crystalline cones for an object at different distances and its size decreased as the object distance increased. For the lightadapted crystalline cones the range of object distance became smaller and the brightness of superposition image became lower than they were with dark-adapted crystalline cones. Bleached crystalline cones could form a superposition image only at a certain distance and the bright ness of image was lowest in the three cases. Differem number of crystalline cones could form the same superposition image but the increase in image sharpness arose from the increase in　umber of the crystalline cones. According to the observation in the field of part of the compound eye and the characteristics of its structa re, the field angle of the compound eye of the Beijing firefly was found to be over 180°

Key words: Phrococelia pekinesis——compound eye——crystalline cone——optical ina- aging-superposition image