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 insect. In another flower little flies were crawling about, and I
saw them leave pollen on the stigmas.
I do not know whether Lepidoptera generally keep to the flowers of the
same species; but I once observed many minute moths (I believe Lampronia
(Tinea) calthella) apparently eating the pollen of Mercurialis annua,
and they had the whole front of their bodies covered with pollen.
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