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Darwin Correspondence Project

From Hermann Müller   4 September 1876


Sept. 4., 1876.

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.


Francis Darwin’s paper ‘On the hygroscopic mechanism by which certain seeds are enabled to bury themselves in the ground’ (F. Darwin 1876c) had been read at the Linnean Society on 16 March 1876 and published in the society’s transactions. His paper ‘The process of aggregation in the tentacles of Drosera rotundifolia’ (F. Darwin 1876b) appeared in the Quarterly Journal of Microscopical Science. Drosera rotundifolia is the common or round-leaved sundew.
Müller evidently sent the last two instalments of his series of articles ‘Die Bedeutung der Honigbiene für unsere Blumen’ (The importance of honey-bees for our flowers; H. Müller 1875–6), published in the June and July 1876 issues of Bienen-Zeitung.
See letter from Hermann Müller, 16 February 1876 and n. 2. Bombus terrestris is the buff-tailed bumble-bee and Trifolium pratense is red clover. Müller probably uses the term ‘hive-bee’ to refer to Apis mellifera, the European honey-bee, but the term can more generally refer to any species of social bee.
Bombus lapidarius is the red-tailed bumble-bee; B. sylvarum is the shrill carder bee; B. agrorum (a synonym of B. pascuorum) is the common carder bee.
Bombus mastrucatus (a synonym of B. wurflenii) is a bumble-bee found in mountainous regions of northern Europe. Müller had described how B. terrestris gnawed through the base of the corolla tube of flowers of red clover in H. Müller 1873, p. 223.
Trifolium praetense var. nivale is a synonym of T. praetense var. villosum. Aconitum napellus is monkshood; A. lycoctonum is northern wolfsbane; Silene inflata (a synonym of S. vulgaris) is bladder campion.
Orchis globosa (a synonym of Traunsteinera globosa) is the globe orchid. Gentiana bavarica is Bavarian gentian; G. verna is spring gentian; G. nivalis is snow gentian.
Daphne striata is fairy garland flower; Primula farinosa is the bird’s-eye primrose.
Müller’s book Alpenblumen, ihre Befruchtung durch Insekten: und ihre Anpassungen an dieselben (Alpine flowers, their fertilisation through insect agency and adaptations for this; H. Müller 1881) was published in 1881.


Müller, Hermann. 1873. Die Befruchtung der Blumen durch Insekten und die gegenseitigen Anpassungen beider. Ein Beitrag zur Erkenntniss des ursächlichen Zusammenhanges in der organischen Natur. Leipzig: Wilhelm Engelmann.

Müller, Hermann. 1875–6. Die Bedeutung der Honigbiene für unsere Blumen. Bienen-Zeitung: Organ des Vereins der deutschen Bienenwirthe 31 (1875): 81–2, 102–4, 109–11, 122–5, 138–41, 165–9; 32 (1876): 20–2, 119–23, 176–84.

Müller, Hermann. 1881a. Alpenblumen, ihre Befruchtung durch Insekten: und ihre Anpassungen an dieselben. Leipzig: W. Engelmann.


Bombus mastrucatus, an alpine bee, conforms to his observations that B. terrestris breaks open the flowers of Trifolium pratense. However, in the Alps, B. terrestris does not behave this way.

Gentiana species are adapted to lepidopteran cross-fertilisation.

Letter details

Letter no.
Heinrich Ludwig Hermann (Hermann) Müller
Charles Robert Darwin
Sent from
Source of text
DAR 171: 306
Physical description
ALS 4pp

Please cite as

Darwin Correspondence Project, “Letter no. 10589,” accessed on 23 June 2024,

Also published in The Correspondence of Charles Darwin, vol. 24