My dear Sir,

A fortnight ago, returning from an excursion into the Alps, I received two very interesting memoirs of your son Francis “on the hygroscopic mechanism by which certain seeds are enabled to bury themselves in the ground”, and “the process of aggregation in the tentacles of Drosera rotundifolia”.¹ As I do not know his adress I would beg you to say him my sincere thanks for his kindness and to give him in return the spare copie of my two last memoirs on bees which I will send you today.²

I have promised you to repeat my observation on the behaviour of Bombus terrestris and the hive-bee on the flowers of Trifolium pratense.³ But unfortunately on the meadow which I passed daily when going to my bathing-place, I found Trifolium pratense exclusively visited by Bombus lapidarius, silvarum and agrorum, which all three gain its honey in the legitime way.⁴ Not a single hive bee, not a single Bombus terrestris was there to be seen on Trifol. pratense. It was therefore with great pleasure that I saw, in the Alps, Trifolium pratense var. nivale very frequently visited by an alpine humble bee, Bombus mastrucatus Gerstaecker, which treated its flowers in exactly the same manner as I have described, in my book on fertilisation p. 223, concerning Bombus terrestris.⁵ I add some heads of this Trifolium on which I have seen working Bombus mastrucatus; you will find some flowers of these heads broken open in the described manner.

In the Alps Bombus terrestris seems to have remarkably other customs than in the plain; for, although it is met with sufficiently frequently in the Alps, there I have never seen it breaking open forcibly flowers containing their honey in a long tube or spur; whereas Bombus mastrucatus, an exclusively alpine species, shows here the same thievish inclination as B. terrestris in the plain. It breaks open the honey-vessels not only of Trifol. pratense var. nivale, but also of Aconitum Napellus, Ac. Lycoctonum, Silene inflata⁶ and many other flowers.

In this excursion I have found that also Orchis globosa and some alpine Gentiana species (bavarica, verna, nivalis) are adapted to crossfertilisation by Lepidoptera;⁷ the most inconspicuous of these three Gentiana species, G. nivalis, regularly fertilising itself, in case visits of Lepidoptera are wanting. I succeeded also in observing directly the fertilisers of Daphne striata, Primula farinosa and the above named plants.⁸ After one or two more excursions into the Alps I will finish my researches on “Alpenblumen und ihre Befruchtung durch Insekten”.⁹

As soon as I have succeeded in observing anew the behaviour of Bombus terrestris and the hive bee on the flowers of Trifolium pratense I will give notice to you.

My dear Sir | yours very sincerely | H. Müller.