I20 



INTRODUCTION 



Fig. 29. Syntphoricarpos 

 rvcemosus, Michx.^ a Wasp 

 Flower. 



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 

 inserted in the opening of the flower (which is precisely 

 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 Muller'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 

 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 brownish floral colour has a very special attraction 

 for wasps. The ventricose tiec tar -pouch filled with ahunda7it nectar is also character- 

 istic oi wasp flowers. Symphoricarpos racemosus, which has already been mentioned, 

 also possesses such a nectar-receptacle, and so does Cotoneaster vulgaris Lindl. 

 (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 eff'ecting cross-pollination. Miiller did not 

 observe other visitors. 



Fig. 30. Scrophularia nodosa^ Z,., a Wasp 

 Flower. 



