40 
THE .TOUItNAL OF BOTANY 
In addition to the many small animals mentioned, various ex- 
traneous objects also frequently find their way into the cups. Thus 
Kerner {op. cit. i. p. 156) writes that in them “ there is invariably 
a collection of dust-particles, small dead animals, pollen-grains, etc., 
which have been blown in by the wind ; whilst rain, trickling down 
the stems, brings very various objects with it from higher up and 
washes them into these reservoirs in the leaves. Sometimes, too, a 
few animals are drowned in the receptacles.” 
Mr. Robert Paulson informs me that he has observed in the cups 
fungus-spores, unicellular algai, pollen-grains, and seeds of a grass 
{Holcus lanatus ), some of these latter actually germinating therein 
in the autumn. In late summer and autumn, I have often found in 
the cups a considerable number of the plant’s own corolla-tubes, which 
fall as the flowering-sea son advances. 
There is, however, one Order of Insects of which one might, at 
first sight, expect to find examples in the cups of the Teasel, but 
which are practically never found therein — namely, the bees 
(Hymenoptera). This is, in one way, surprising; for, as stated 
already, the pollination of the flowers is effected largely by these 
insects, which are to be seen constantly visiting its flowers and might 
easily fall in. Yet their absence from the cups is not really sur¬ 
prising ; for these bees are clean feeders and are, therefore, not at all 
likely to be attracted by the fetid liquor, as the foul-feeding flies 
(Diptera) seem to be. In any case, I have only once found a 
bee dead in the liquor—an individual of Pombus clerh a melius <$ 
(identified by Mr. C. Nicholson), which I found in one of the cups 
of a plant growing in the Grays chalk-pits on 17th August 1922. 
I assume that it had fallen in accidentally whilst visiting the flowers 
of the plant. Sir Francis Darwin does not mention having met with 
any bees in the cups. 
The water-cups offer, one would have thought, ideal breeding- 
places for mosquitoes ; but these creatures never use them as such in 
this country, so far as my observations go. The late Mr. Arthur 
Bacot, who had given much attention to the breeding of mosquitoes, 
informed me, shortly before his recent death, that he knew of no 
instance of their so doing. Yet in America a species of mosquito and 
certain other insects elsewhere are known to breed in very similar 
situations.- Thus, there are various species which lay their eggs 
habitually and exclusively in the pitchers of certain species of both 
Nepenthes and Sarracenia, the grubs, when hatched, living in and 
upon the putrescent liquor existing therein, subsequently eating their 
way through the walls of the pitchers and pupating in the earth. 
The first to call attention to this curious fact was Dr. Charles Y. 
Riley, who recorded the habit in connection with a Flesh-fly ( Sarco - 
phaga sarracenice Riley), which thus uses the pitchers of Sarracenia 
flava and S. variolans (see Trans. Acad. Sci. St. Louis, iii. pp. 235- 
240: 1875). At least two other species of Flesh-fly {S. rileyi 
Aldrich and S.jonesi Aldrich) are known to do the same (see Aldrich 
in Publications of the Thomas Say Foundation , i. pp. 86, 241, and 
242 : La Fayette, Ind. 1916). An American species of mosquito 
( Wyeomia smithii) makes a similar and exclusive use of the pitchers 
