PART IV. | GENERAL RETROSPECT. 595 
The Jchnewmonide at first surpassed all other visitors in obser- 
vation and discernment, and they were thus able to produce 
inconspicuous flowers which escaped the notice of other visitors. 
On the appearance of sand-wasps and bees these inconspicuous 
flowers were banished by competition to the less frequented 
localities (¢.g., Listera to shady woods). 
The Sand-wasps (Sphegidw) apparently took the place to a 
great extent of the Ichneumons, and produced flowers where 
organs had to be thrust apart (Papilionaceze), or where a narrow 
cavity had to be entered (Labiate), or where some other action 
similar to the act of digging had to be performed. Subsequently 
bees seem to have entered on joint possession of most of these 
flowers, and to have added special adaptations of their own. 
The true Wasps (Vespidw) could establish themselves by the 
fear of their sting (and of their jaws) in sole possession of certain 
flowers with wide open mouths and abundant honey. These they 
developed farther in relation to their wants (Serophularia, Sym- 
phoricarpus, Epipactis latifolia, Lonicera alpigena); but where 
wasps are scarce the flowers are utilised by other insects. 
Bees (Apidae), as the most skilful and diligent visitors, have 
played the chief part in the evolution of flowers; we owe to 
them the most numerous, most varied, and most specialised forms. 
Flowers adapted for bees probably surpass all others together in 
variety of colour. The most specialised, and especially the gre- 
garious bees, have produced great differentiations in colour, which 
enable them, on their journeys, to keep to a single species of flower. 
While those flowers which are fitted for a miscellaneous lot of 
short-lipped insects usually exhibit similar colours (especially 
white or yellow) over a range of several allied species, the most 
closely allied species growing in the same locality, when adapted 
for bees, are usually of different colours and can thereby be 
recognised at a glance (¢g., Trifolium, Lamium, Teucrium, 
Pedicularis), 
Some Drone-flies (Syrphide) also, which admire bright colours 
and are themselves brightly adorned (Ascia, Melanostoma, 
Sphegina, etc.), have produced special flowers suited to their 
tastes, which they mainly fertilise (Saxifraga rotundifolia, S. 
umbrosa, etc.); sometimes we even find a special and simple 
mechanism adapted for them (Veronica Chamedrys). 
The power to distinguish red, violet, and blue colours must 
have been acquired to a certain degree by flesh-flies and carrion- 
flies in seeking their natural food; but in other flower-loving 
Q@Q2 
