102 
THE COLOURS OF FLOWERS 
Of these, red and blue are probably the highest types, and 
are found chiefly in flowers of high organisation. 
In dealing with the question of the colour-sensitiveness 
of the eyes of insects we must remember the limitations of 
our own. There is good reason to believe that many insects, 
and especially bees, see as colours the ultra-violet rays of the 
spectrum which are invisible to us. Bees show a decided pre- 
ference for blue colours, butterflies for red and white (the 
only blue Lepidoptera-flower known is Globularia), but be- 
yond this there is but little colour-preference in insects. 
Carrion flies go to meat-coloured flowers, but probably be- 
cause of their carrion smell. We shall probably not be far 
from the mark if we say that the only preference shown by 
insects of low organisation is for bright rather than dull 
colours (they visit many dull flowers, e.g. Adoxa, but it is 
doubtless the smell that attracts). This being so, it is impro- 
bable that the earliest flower-visiting insects had much influ- 
ence upon the colours of flowers ; they would select the most 
conspicuous but would not necessarily produce any direct 
effect on colours. We may therefore probably assume that 
the early flowers were yellow and white, with perhaps a few 
orange or red species. When the higher forms of insects 
appeared, there would be a colour-selection and now we can 
imagine red and blue flowers appearing by the selective action 
of insects. It may be noted that most blue flowers belong to 
class H, the rest chiefly to classes B and B' ; these are the 
classes visited by bees. Most red flowers are found in 
class F, and many in B, B' and H. 
In this connection mention must be made of the honey- 
guides or pathfinders seen in so many flowers — lines, streaks, 
or spots pointing to the entrance to the honey, and differently 
coloured from the rest of the corolla. In Myosotis sp. there 
is a yellow ring at the mouth of the tube, the rest of the 
corolla being blue 1 , in Pelargonium there are reddish streaks 
on a pink ground, in Viola light streaks on a deep blue, and 
so on. These markings as a rule show the way to the honey, 
and are doubtless useful to visiting insects, and hence, by 
increasing the rate at which they work, to the flowers them- 
1 A classic example, for it was one of C. K. Sprengel’s first 
discoveries ; see liis Entdecktes Geheimniss d. Natur , or biography in 
Nat. Science, April, 1893. 
