420 HABITS OF INSECTS CHAP. XL 



of the same species with almost as much regularity as 

 do bees ; and when captured they are found covered 

 with pollen. I have seen Wiingia rostrata acting in 

 this manner with the flowers of Lychnis dioica, Ajuga 

 reptans, and Vicia sepium. Vdlucella plumosa and Empis 

 cheiroptera flew straight from flower to flower of Myosotis 

 sylvatica. Dolichopus nigripennis behaved in the same 

 manner with PotentiUa tormentilla ; and other Diptera 

 with Stellaria holostea, Helianthemum vulgare, Bellis 

 perennis, Veronica hederssfolia and cliamoedrys ; 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-fertili- 

 sation 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 appa- 

 rently 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 



