HOVER-FLY FLOWERS 



135 



the insect alights upon another flower, to be once more deceived, the poUinium 

 sticking to its head has in the meanwhile curved downwards in such a way that 

 it will strike the stigma, and thus effect pollination. 



A final example is afforded by Paris quadrifolia, which has been recognized as 

 a Deceptive Fly Flower by Hermann Mtiller (Kosmos, ii, 1877, p. 336). The offensive 

 odour at once suggests that flies are the visitors. In the middle of the flower, the 

 dark purple pistil, which is crowned by four stigmas similarly coloured, shines as 

 if it were wet with fluid and thus entices flies that like decomposing substances, 

 e.g. Scatophaga merdaria F. To such insects the idea is suggested that here 

 ma)' be found the putrid matter they eagerly desire. The four greenish-yellow 

 linear petals hang down like narrow lappets from the flower, often almost far enough 

 to touch the four foliage leaves. They are regarded by Hermann Miiller (op. cit.) 

 as guide-ropes for small gnats, which are led by them into the middle of the flower 

 to the deceptive ovary. The erect stamens surrounding the centre of the flower, 

 are thought by this investigator to serve as perches up which the flies creep, and 

 so get covered with pollen. On several occasions Hermann Miiller actually observed 

 a small gnat (Ceratopogon ?) and a few Muscidae (among them Scatophaga 

 merdaria/^.) flying to the flowers, and busying themselves chiefly with the ovary, 



Fig. 50. Veronica Chamatdrys, L., a Hover-fly Flower. A. Flower seen from the front. B. The 

 same with stamens placed together. C. The same with Ascia podagrica F., which has drawn the stamens 

 together under its body, in the manner indicated in B. D. Pistil with nectaries (x 3). 



and sometimes with the stamens. But the little insects were so shy that it was 

 only possible to observe them from a distance, and the entire sequence of their 

 operations in the flowers could never be seen. Hermann Miiller concludes from 

 his observations that at least the most important part of the process may be 

 considered settled, i.e. that the pistil, although it offers no food, serves to entice 

 certain Diptera, so that Paris belongs to the Deceptive Flowers. This greatly 

 increases the probability of the interpretation given above in respect of the floral 

 adaptations of Ophrys muscifera (Kosmos, ii, 1877, p. 337). 



E. Hover-fly Flowers (Fh). 



Hover-fly Flowers are beautifully coloured, marked by radiating streaks and 

 possessing a decorative, sharply defined centre. Their delicate mechanism for 

 pollination is put into action by hover-flies as elegantly coloured as themselves. 



