| The mechanism of photosensitivity and phototaxis of the dominant predatory enemies Propylea japonica (Thunberg) in many farmlands and orchards was investigated by means of microscope, histology and electrophysiology. The results are as follows:1 The compound eyes distributed the upside lateral of the head slightly convergent posteriorly. Each compound eye was composed of approximately 630 ommatidia. Each ommatidium consisted of a cornea, a cone, six to eight retinula cells, and a basal cell. The surrounding of the crystalline and the retinular pigment cells contained abundant pigment granules.2 The longitudinal section of the whole rhabdom showed that the pigment granules in the distal and proximal ends were more than those in the intermediate region relatively. In the light-adapted state, the pigment granules distributed in the most regions around the rhabdoms evenly. However, the distribution of the pigment granules was mainly around the distal region of the rhabdoms in the dark-adapted state, indicating that it had some characters of superposition eyes. No differences were observed between the sexes.3 The spectral sensitivity and intensity response from P. japonica were studies by using ERG's extracellular recording method. The result showed the monochromatic light stimuli with the different wavelengths within U.V. and most visible light region, including the range of 340-360nm, can induce ERG reactions with different amplitudes. According to the size of the amplitude of relative intensity Log I (perk-perk value), there are three different perks in its spectral sensitivity curves, the major perk appearing at 562nm (yellow-green), the second 524nm and the third 460nm (blue) and the major perk value was almost equal to the second, indicating that P. japonica may own two or three types of photoreceptor.4 The intensity could influence the ERG values of the compound eye of P. japonica. The result indicated that within a certain range of intensity, the ERG would augment with the increase of the intensity of the stimuli of white light. The change of the prophase was not evidence, but the anaphase was the current of "quick-slow", so the whole curve appeared the near "J" shape, showing that the compound eye of P. japonica had quite strong abilities of self-adjustment intensity and light-resistant.5 The sexes, intrinsic diurnal rhythm of P. japonica and the dark-adapted time wouldhave some effects on the values of ERG of the compound eye of P. japonica. In the same conditions, the ERG value of the male adult was larger than the female;the ERG value of the adult on night was larger than the one in day;the ERG value would increase with the dark-adapted time and made stability in end. Every ladybird needed the different time to make the value of ERG stabilization, namely it needed about 120 min in day and 100 min on night. This might be relative to the rate of pigment movement in the different unit of the same species in day or on night.6 ERG consisted of four parts in the compound eyes of P. japonica: on light reaction, positive potential, long negative potential and off light reaction, but the off light reaction was very small and was hardly seen. Their size and shape could be influenced by wavelength, light-intensity and stimulation time.
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