120 INTRODUCTION 
flower was visited very eagerly by wasps at the beginning of its floral period, while 
later on honey-bees and humble-bees were the principal visitors. Robertson made a 
similar observation in Illinois, but he found that at the end of August and beginning 
of September, when the flowers were beginning to get scarce, wasps once more 
appeared as their only visitors. He concludes as follows:—‘ This seems to be 
significant, for when any flower becomes reduced in 
numbers, its proper visitors are apt to be the last to 
leave it’ (Trans. Acad. Sci., St. Louis, Mo., v, 1891). 
I have called attention (‘ Bliitenbesucher,’ I, p. 17) 
to the fact that the yellow anthers and brownish corolla 
of Scrophularia harmonize in a remarkable way with 
the colours of the insect visitors. A wasp with head 
Fic. 29. Symphoricarpos inserted in the opening of the flower (which is precisely 
ao al Michx.,a Wasp  —_— adapted to it) and projecting abdomen looks almost as if 
it were a part of the flower, so far as colour is concerned. 
The flowers of Lonicera alpigena are coloured in a similar way to those of 
Scrophularia nodosa and S. aquatica (see Fig. 31). 
According to Hermann Miiller’s account (‘Alpenblumen,’ pp. 395 and 396) the 
flower-bud is reddish-brown. When the flower opens this colour is replaced for 
a short time by the dirty yellowish-white of 
the inner surface, while in the older flower 
this assumes the reddish-brown colour pos- 
sessed by the outer surface. It consequently 
follows that the groups of flowers, taken 
collectively, exhibit the reddish-brown colour 
that is elsewhere uncommon, but resembles: 
that which we find in Scrophularia. About 
I mm. above its base the corolla secretes 
iat a See eee mace. “.aWasp nectar very abundantly, in a ventricose ex- 
pansion, which is exactly wide enough to 
receive the head of a wasp or*humble-bee. Hermann Miiller observed that in the 
Alps two species of wasps were particularly common visitors. 
The flowers of Epipactis latifolia also possess a similar colouring. Charles 
Darwin (‘Orchids’) observed that wasps (Vespa sylvestris) visited this species. It 
would appear, therefore, that the drownzsh floral colour has a very special attraction 
for wasps. The ventricose nectar-pouch filled with abundant nectar is also character- 
istic of wasp flowers. Symphoricarpos racemosus, which has already been mentioned, 
also possesses such a nectar-receptacle, and so does Cotoneaster vulgaris Zzndl. 
(Fig. 32), which, according to Hermann Miiller (‘Alpenblumen,’ pp. 214, 215), is to 
be regarded as a wasp flower. The small pale red flower is shaped like a hemi- 
spherical cup, of which the yellow, fleshy inner wall secretes nectar very freely, and 
this is sought with avidity by a wasp (Polistes biglumis). This insect, which cements 
its nest to the rocks on which the Cotoneaster grows, was seen by Hermann Miiller 
to wander very frequently from flower to flower, sinking its head in the nectar-cup 
(that exactly corresponds in size), and thus effecting cross-pollination. Miiller did not 
observe other visitors. 
