THE ENTOMOLOGIST. 337 



double function of sucking honey and eating pollen. In the 

 Tipulariae, and also in those Hies which do not eat pollen, 

 but live exclusively upon juices, for instance, Boinbylius, 

 the two valves of the proboscis serve no other purpose than 

 to protect and guide the sucking-tubes; but in the flies which 

 devour pollen, besides this formation there is also that of 

 grinding the pollen, for which they have special adaptations, 

 for the margins of the two valves at the point of union are 

 transversely dentate with fine and parallel bands of chitine. 

 Probably the greater or less distance of these bands in 

 different species is related to the diflferent size of the pollen 

 upon which they feed. — Discourse delivered hij Dr. Erm. 

 Midler., of Lippsiadt, to the l\teniy-sixth General Assembly 

 of the Natiirhislorischen Verein fur RJieinsland und West- 

 phalen, 18G9. Trajislated into Ilalian from ilie German, 

 tuiiJi annotations hi/ Professor Frederic Delpino. Trans- 

 lated for the 'American Naturalist' by. R. L. Packard. 



[My kind friend, Mr. A. W. Bennett, wdio is now engaged 

 in studying the fertilisation of plants by insects, has sup- 

 plied nie with the above extract, in reference to my note, 

 intituled the " Food of Eristalis," in the January number of 

 the ' Entomologist' (Entom. vi. 291). It is wonderful that we 

 should be compelled to gain information of this kind through 

 such a variety of channels, — German, Italian, and American, 

 — when the phenomena described are to be observed daily in 

 our own gardens, at our own doors. Even at the present 

 hour some of our leaders in Entomology are contending the 

 facts, because at variance with their own hypotheses. The 

 duty assigned to insects of fecundating hermaphrodite 

 flowers has been observed by Mtiller, Darwin, and many 

 others ; but its modus operandi has certainly not been 

 clearly explained. The great office of such pollen-chewing 

 Diptera as Eristalis is not to fecundate the individual 

 blossom which appears to undergo this spoliation, but to 

 transfer the fecundating principle from one plant to another. 

 In accordance with a law which is revealed in every variety, 

 race, or s))ecies, depauperation is always at work, and no 

 gardener, whatever his views, can possibly overlook the fact 

 that if he attempt to produce continuously any particular 

 species or variety from the seed of one plant he will fail, 

 because of this tendency. The various beautiful asters, or 



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