13- 



apple structure. The only structure which we could not mimic was 

 the pink tissue of developing blossoms, which had a reflectance 

 pattern unlike that of pink, red, or any other paint. We then applied 

 the paints to 6x8 inch cardboard rectangles, coated the rectangles 

 with a clear sticky substance (formerly known as "Bird Tanglefoot" 

 but now called "Tangletrap") to capture alighting TPBs, and hung 

 the rectangles by wire from low apple tree branches at knee to waist 

 height. 



The results of this test showed that TPB adults alighted in 



greatest numbers on white, clear Plexiglas, 

 and in lesser numbers on gray, green, blue, 

 rectangles (table 3). 



TABLE 3 



and yellow rectangles, 

 red, orange, and black 



Color of 

 Rectangle 



No. TPB adults 

 captured 



The white paint reflected light in the same general pattern as 

 bud scales, newly unfolding leaves, the calyx cup, and mature blossom 

 petals. The intensity of reflection from the white w^as greater than 

 from bud scales, etc., hence giving it the appearance of very bright 

 bud scales, etc. The yellow paint reflected light in the general 

 pattern of maturing leaves, but likewise, at greater intensity. The 

 fact that clear Plexiglas captured just as many TPBs as the white and 

 yellow rectangle suggests that TPBs were not actually attracted by 

 the white and yellow surfaces. Rather, it appears that TPBs were 

 repelled by colors such as red, orange, and black, which have reflec- 

 tance patterns similar to those of twigs and bark, upon which TPBs 

 do not feed. 



Additional tests revealed that like sawfly adults, TPB adults 

 discriminate between different types of white surfaces. No apple 

 structures reflect an appreciable amount of ultra-violet (UV) light. 

 Consistent with this was our finding that TPBs readily alighted on 

 white-painted rectangles reflecting a low amount of UV, but were 

 repelled by white-painted rectangles reflecting moderate or substan- 

 tial UV. Although to the human eye, IN and non-UV reflecting white 

 paints are indistinguishable, to the eye of TPB, they obviously are 

 distinguishable. As things have turned out, the same low-UV-ref lecting 



