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Show 416 HABITS OF INSECTS CHAP. XI. h. -bee more than 2000 years ago, and was noticed bIy v eD obbs in a paper pubh·s hed I· n 173 G 1· n t h e I:>hI'l o - sophical rrransact.ions. It nlay be o~served by any one, both with hive and h~m?le-b. es, 1n every flowergarden; not that the habit 1s 1nvana~ly followed . . 1\Ir. Bennett watched for several hours n1any plants of Lan~ium album, L. puYpureum, and another L::tbiate plant, Nepeta glechoma, ~ll growing mingled together on a bank near some ht ves ; and he found that each bee confi.ned its visits to the same species. The pollen of these three plants differs in colo~r,. so that he ':as able to test his observations by exanlining that whiCh adhered to the bodies of the captured bees, and he found one kind on each bee. Humble and hive-bees are good botanists, for they know that vari ties may differ widely in the colour of their flowers and yet belong to the same species. I have repeatedly seen humble-b~es flying stra~ght from a plant of the ordinary red n~ctwmnus frax~~ella to a white variety; from one to another very differently coloured variety of Delphinium consoli~a and of Primula veris ; from a dark purple to a bnght ~ellow variety of Viola tricolor; and with two. spe~ws of Papaver, from one variety to another which differed 1nuch 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. H. 1\fi.lller also has seen hive-bees flyino· from flower to flower of Ranu~culus bulbosus and a~vensis, and of Trifolium fragifen~m and repens; and even from blue hyacinths to blue violets.t Some species of Di ptera or flies keep to the flowers * 'Nature,' 1874, June 4th, p. 92. t '~en~n Zcitung,' July 1876, p. 18B. CHAP. XI. IN RELATION TO CROSS-FERTILISA'I'ION. 417 of the san1e species with almost as Inuch reg 1 ·t . u any as d~ bees, and when captured they are found covere 1 With pollen. I have seen Rhingia rostrata act· · . . 1ng 111 this JI?.anner WIth the flowers of Lychnis dioica A · t d TT.. • • , JUfja rep.ans, an r ~c~a sernum. Volucella plumosa and Empis che~roftera flew. straight ~ro~ flower to flower of Myosotis sylvatwa. Dol whop us n~gnpennis behaved in the same manner with Potentilla tormentilla; and other Diptera with ~tellaria . holostea, Helianthemum vulgare, Bellis perenn~s, Veronwa hedermfolia and chamoodrys; but sOine flies visited indifferently the flowers of these two latter s~ecies .. I have s.een m~re than once a minute Thrips, with pollen adhenng to 1ts body, fly fr01n one flower to another o~ the same k.in~ ;· and one was observed by me crawhng about w1thin 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 n.ot 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 A.rum maculatum are furnished with filaments apparently adapted to prevent the exit of insects, they resemble in this respect the flowers of Aristolochia; and o~ examining several spathes, from thirty to sixty ~rnnute Diptera belonging to three species were found In some of them; and many of these insects were lying dead at t~e bottom, as if they had been permanently entrapped. In order to· discover whether the living ones could escape ancl .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 tin1e several little flies were crawling about on the Inner 2 E |