206 SUPPLEMENT TO THE INTRODUCTION 
In none of these cases is Plateau justified in the general inference that the 
colours of flowers play no part in attracting insects. The only conclusion to be 
drawn is that in flowers of the same shape the colour is a matter of indifference to the 
visitors, and that these possess an exceedingly well-developed sense of form. The 
honey-bee, as is well known, and as Hermann Miiller repeatedly points out, after once 
making a beginning keeps with great constancy to one species of flower, sucking this 
alone to the exclusion of all others which may be present. And that in this it is of 
guided by odour but by colour and form appears from the circumstance that it often 
makes indiscriminate visits in the case of flowers that are similarly formed though of 
different species, e.g. Sinapis arvensis and Raphanus Raphanistrum, which cannot, 
however, be supposed to possess the same odour. 
The fact that according to Plateau’s further experiments very conspicuous 
flowers, which as a rule receive few visitors (e.g. Pelargonium zonale Wrl/d., Phlox 
paniculata Z., Anemone japonica Sveb. e¢ Luce., Convolvulus sepium Z.), attract large 
numbers when honey zs put upon them, only proves that the odour of honey exercises 
a great power of attraction upon insects, which has long been known. It is only 
necessary to place honey anywhere to secure the immediate appearance of numerous 
insects which are fond of it. 
In a similar way may be explained Plateau’s numerous experiments on anemo- 
philous flowers, by adding diluted honey to which numerous insects were attracted. 
When Plateau further proved that insect visits ceased after removal of the nectar-pro- 
ducing structures (of dahlias), but began again when nectar was reintroduced—Bombus, 
Megachile, and Vespa making their appearance—he confirmed the well-known fact 
that insects can accurately distinguish between the nectarless and nectar-yielding 
flowers of a given species. On this point Hermann Miiller writes as follows 
(‘Weitere Beobachtungen,’ III, p. 13):—‘Honey-bees and humble-bees when 
despoiling Cerinthe minor display their great skill in recognizing small differences 
between flowers. Some of the flowers that have been visited, and in which the pyramid 
of stamens is pressed apart at the apex, they fly past without touching, others they 
touch in passing only to leave again immediately. They fly with extended proboscis, 
humming as they go, and steadily searching from flower to flower, till they have 
found one filled with nectar. From this it appears that insects can see extremely 
well at a short distance, and that they are led by sight to the flowers they visit. 
The recognition of artificial flowers by insects obviously depends upon this 
appreciation of very minute differences, and involves doth sight and smell. It is 
accordingly not to be wondered at that insects should not have visited the artificial 
flowers of Ribes sanguineum Persh., Persica vulgaris J@Z/., Cerasus vulgaris AZIL., 
Myosotis alpestris Schm., Pyrus Malus Z., Saxifraga umbrosa Z., Digitalis purpurea 
Z., and Lathyrus latifolius Z., which were placed by Plateau among natural flowers 
of the same species, but left them unheeded, even when provided with honey. 
Though these artificial flowers may seem very realistic to human eyes, yet insects are 
not to be deceived, for the surface of such flowers appears quite different on close 
inspection from that of natural ones, and their odour—due to the materials of which 
they are made—is easily perceived by insects, though perhaps not by us. 
Two causes, one due to sight, the other to smell, prevent insects from visiting 
artificial flowers, just as—according to the observations of Hermann Miiller on 
