Chapter 11 - Page 2

tricolor; and with two species of Papaver, from one variety to another which differed much in colour; but in this latter case some of the bees flew indifferently to either species, although passing by other genera, and thus acted as if the two species were merely varieties. Hermann Muller also has seen hive-bees flying from flower to flower of Ranunculus bulbosus and arvensis, and of Trifolium fragiferum and repens; and even from blue hyacinths to blue violets. (11/3. 'Bienen Zeitung' July 1876 page 183.)

Some species of Diptera or flies keep to the flowers of the same species with almost as much regularity as do bees; and when captured they are found covered with pollen. I have seen Rhingia rostrata acting in this manner with the flowers of Lychnis dioica, Ajuga reptans, and Vici sepium. Volucella plumosa and Empis cheiroptera flew straight from flower to flower of Myosotis sylvatica. Dolichopus nigripennis behaved in the same manner with Potentilla tormentilla; and other Diptera with Stellaria holostea, Helianthemum vulgare, Bellis perennis, Veronica hederaefolia and chamoedrys; but some flies visited indifferently the flowers of these two latter species. I have seen more than once a minute Thrips, with pollen adhering to its body, fly from one flower to another of the same kind; and one was observed by me crawling about within a convolvulus with four grains of pollen adhering to its head, which were deposited on the stigma.

Fabricius and Sprengel state that when flies have once entered the flowers of Aristolochia they never escape,--a statement which I could not believe, as in this case the insects would not aid in the cross-fertilisation of the plant; and this statement has now been shown by Hildebrand to be erroneous. As the spathes of Arum maculatum are furnished with filaments apparently adapted to prevent the exit of insects, they resemble in this respect the flowers of Aristolochia; and on examining several spathes, from thirty to sixty minute Diptera belonging to three species were found in some of them; and many of these insects were lying dead at the bottom, as if they had been permanently entrapped. In order to discover whether the living ones could escape and carry pollen to another plant, I tied in the spring of 1842 a fine muslin bag tightly round a spathe; and on returning in an hour's time several little flies were crawling about on the inner surface of the bag. I then gathered a spathe and breathed hard into it; several flies soon crawled out, and all without exception were dusted with arum pollen. These flies quickly flew away, and I distinctly saw three of them fly to another plant about a yard off; they alighted on the inner or concave surface of the spathe, and suddenly flew down into the flower. I then opened this flower, and although not a single anther had burst, several grains of pollen were lying at the bottom, which must have been brought from another plant by one of these flies or by some other