j *@ - Sociedade Brasileira de Psicologia

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M mpestris are maximnlly sensitive at 328nm, 456nm, 532nm and 596nm , and the
functions of the UW , blue, and green cells follow the theoretical absorption of the
corresponding rhodopsins. However, the red receptor is much nlrrower and this may
be due to some screening effects, in that the green receptor mny screen the red cell
in the shorter part of the spectrum which results in a steeper fundion. Metarhodopsin,
which probably mninly absprbs at 490nm (Staveng: & SchFemer, 1984) nmy also
have a screening effect. 'Ihe longer part may be changed by a red screening pigment
which shifts green absorbing pigments to a longqr wavelength. Green and red cells
show also a second maximlm at about 3701m Fltich cmn be explained by the j-peak
of the rhodopsins. .
We also used our model to calculate the chromaticity diagram and the colour
discriminability function for > four dimensional colour space, but behavioural experiments
still need to be completed. . .
The solitary Brazilian bee, Calonychium pemnfce (recordings by D. Ventura),
also has four different receptor types. Here the Uv-receptor is shiftqd to a longer
wavelength (363nm) than that observed foy other Hymenopterans, whereas the blue
receptor is shifted to the shorter part of the spectrum (404nm). Tlzis would suggest a
physiological or Mrtifactual electrical coupling between these tFo receptoctypes. Even
at longer wavelengths the blue receptor shows a hlxmp and som: sensitivity up to
590nm which may also be explicable by coupling effects. 'lhe p'efn receptor has
maxim um sensitivity at 533nm . In contrast . to Tenthredo, the red receptor
(X O X= 600nm) folows the theoretical absorption fundion very wel.
Male and femnle Callonychium exclusively visit either orange or red flowers
for meeting other individuals and train themselves to these colours. This behaviour
allows for the testing of th . eir colour discrimination with respect to out model predictions
and investigation of their possibly tetrachromatic colour vision system . Since we
havq pnly recently started such experiments the amount of existing data is limited
X ittmann, pers. commlmicationsl. However, there is some evidence that these insects
a4e able to discriminate yellowerange cplours.
CONCLUSION
Hymenopterans live in different habitats with varying mixtures of light e.g.
ip the tropical rain-forest there is a higher proportion of green light whilst in mountaineolzs
regions there is much more IJV light. On the other hand, some Hymenopterans
(i.e. Calonychîumj are. specialized in visiting only pne or a few. kinds of similar
coloured flowers. In order to achieve the best colour contrut, the mnximllm of one
receptor type should correspond to the background 'hght. Although the spedral
sensitivities of the photoreceptors are slml ' '1 ar, the L X/â-fundions may slightly differ ,
and these small differençe! may Be very important in colour visiqp systems.