TIMOTHY H. GOLDSMITH 111 



TABLE 2 



Insects kor Which the Near Ultraviolet Has Been Observed to be the 



Most Efeective Region ok the Spectrum in Evoking Behavioral 



Responses Such as Phototaxis 



Order Animal and Reference 



Hemiptera Leptocoris* (62) 



(true bugs) 



Coleoptera 18 species (62, 63, 64) 



(beetles) 



Hymenoptera Formica, Lasius (38) 



(bees, wasps, ants, etc.) Apis (5, 62, 9, 28, 20) 



Macrocentrus (62) 



Diptera Drosophila (6, 63, 65) 



(flies) Musca (7) 



Lepidoptera Laspeyresia (42) 



(moths and butterflies) (also 7 of 14 larval forms tested) (64) 



* Near ultraviolet and blue-green lights about equally effective in stimulating photo- 



taxis. 



A maximum of spectral sensitivity at about 340 m/x. in the near 

 ultraviolet occurs in the compound eyes of the cockroach Periplanetn 

 (58, 59) , one fly CnlUphora (58, 59^ (see Fig. 5) , and the honeybee 

 Apis (20) (see Figs. 2 and 4) , as well as the ocellus of the honeybee 

 (23). In each case this maximum reflects the presence of a receptor 

 for ultraviolet light which is one of at least two color receptors present 

 in the eye. For example, the upper part of the eye of the cockroach 

 has peaks of sensitivity in the green and ultraviolet regions of the 

 spectrum. The relative heights of these maxima vary in different 

 dark-adapted preparations and can be made to change in either di- 

 rection by adapting the eye with monochromatic lights (58, 59) . 

 Furthermore, the time course of the retinal action potential is de- 

 pendent on wavelength, being slower at the blue end of the spectrum 

 (56, 57). A similar selective adaptation of the compound eye of the 

 worker honeybee is illustrated in Fig. 2. 



If the maximum in the red is ignored, the spectral sensitivity fun- 

 ction of Calliphom (Fig. 5) is similar to the curves for the phototactic 

 responses of other flies (Fig. 1) . In the case of the honeybee, however, 

 there is another marked difference between the spectral sensitivity 

 function of the dark-adapted eye and the action spectrum for photo- 

 taxis. Often the spectral sensitivity curve of the bee has a single 

 ]:)eak in the green and only a low foot extending into the near ultra- 

 violet (Fig. 2, upper curve) . If the ultraviolet maximum is present 

 in the dark-adapted eye, it is less prominent than the peak in the 

 green (20). 



This observation indicates a potential hazard in determining the 

 properties of receptors from observations of the behavior of the entire 



