tterfly orchis, white jasmine, and a host of others.

4. Bright red flowers are very attractive to butterflies, and are
sometimes specially adapted to be fertilised by them, as in many pinks
(Dianthus deltoides, D. superbus, D. atrorubens), the corn-cockle
(Lychnis Githago), and many others. Blue flowers are especially
attractive to bees and other hymenoptera (though they frequent flowers
of all colours), no less than sixty-seven species of this order having
been observed to visit the common "sheep's-bit" (Jasione montana). Dull
yellow or brownish flowers, some of which smell like carrion, are
attractive to flies, as the Arum and Aristolochia; while the dull
purplish flowers of the Scrophularia are specially attractive to wasps.

5. Some flowers have neither scent nor nectar, and yet attract insects
by sham nectaries! In the herb-paris (Paris quadrifolia) the ovary
glistens as if moist, and flies alight on it and carry away pollen to
another flower; while in grass of parnassus (Parnassia palustris) there
are a number of small stalked yellow balls near the base of the flower,
which look like drops of honey but are really dry. In this case there is
a little nectar lower down, but the special attraction is a sham; and as
there are fresh broods of insects every year, it takes time for them to
learn by experience, and thus enough are always deceived to effect
cross-fertilisation.[147] This is analogous to the case of the young
birds, which have to learn by experience the insects that are inedible,
as explained at page 253.

6. Many flowers change their colour as soon as fertilised; and this is
beneficial, as it enables bees to avoid wasting time in visiting those
blossoms which have been already fertilised and their nectar exhausted.
The common lungwort (Pulmonaria officinalis), is at first red, but later
turns blue; and H. Mueller observed bees visiting many red flowers in
succession, but neglecting the blue. In South Brazil there is a species
of Lantana, whose flowers are yellow the first day, orange the second,
and purple the third; and Dr. Fritz Mueller observed that many
butterflies visited the yellow flowers only, some both the yellow and
the orange flowers, but none the purple.

7. Many flowers have markings which serve as guides to insects; in some
cases a bright central eye, as in the borage and forget-me-not; or lines
or spots converging to the centre, as in geraniums, pinks, and many
others. This enables insect