Ɛpsilon

To Hermann Müller1   14 March 1870

Down, Beckenham, Kent

March 14. 1870.

My dear Sir

I think you have set yourself a new, very interesting and difficult line of research.2 As far as I know, no one has carefully observed the structure of insects in relation to flowers, although so many have now attended to the converse relation. As I imagine few or no insects are adapted to suck the nectar or gather the pollen of any single family of plants, such striking adaptations can hardly, I presume, be expected in insects as in flowers.—3 … Die Wichtigkeit der keinen Pollen verzehrenden Schmetterlinge für die Blumen ist mir niemals eingefallen, und Ihre Gesichtspunkte erklären die ungeheuere Entwickelung der nächtlichen Arten.4 Es scheint mir sehr seltsam, dass es keine nächtlichen blumensaugenden Zweiflügler und Hautflügler geben soll.5 Hat irgend wer den Magininhalt der Fledermäuse untersucht? Nach den Hummeln und Honigbienen, die oft verschiedene Arten besuchen, und nach dem Beispiele der Wespen und der Epipactis latifolia kann ich nicht umhin, zu denken, dass der Geschmack des Nektars die Besuche der Schmetterlinge sogar noch mehr bestimmen muss, als der Bau der Blume.6 Würde es sehr schwierig sein, das Verhältniss der in Deutschland vorkommenden Blumen mit so langen Nektarien oder so verlängerter Röhre, dass sie nur durch Schmetterlinge ausgebeutet werden können, festzustellen? Die in meinem Orchideenbuche versuchte Erklärung der Länge des Nektarium von Angraecum, kann, wie ich vermuthe, auf andere Fälle ausgedehnt werden.7 Sie müssten, denke ich, von Pictet’s oder anderen Werken die frühesten geologischen Formationen festellen, in welchen die verschiedenen Ordnungen der Insekten aufgefunden worden sind.8 Es ist, wie ich glaube, viel Wahres in dem, was ich in einer der späteren Ausgaben des “Ursprungs der Arten” folgerte, dass, bevor Insekten erschienen, die Pflanzen nicht mit ornamentalen Blüthen geschmückt gewesen sind.9 Ich zweifle einigermassen daran, dass irgend eine Beziehung zwischen den glänzenden Farben der Schmetterlinge, ihren Blumenbesuchen und der geschlechtlichen Zuchtwahl bestehe, denn die Geschlechter variiren in der Farbe so häufig im ganzen Thierreich. …

Yours very sincerely | Ch. Darwin

Copy incomplete

1
This letter was previously published in Correspondence vol. 18, with only the English text; the German translation of the rest of the letter has been added from Krause 1884. For a translation of the German of the printed source, see Appendix I.
2
See Correspondence vol. 18, letter from Hermann Müller, 8 March 1870. Müller had sent CD a copy of his paper ‘Die Anwendung der Darwin’schen Lehre auf Blumen und blumen-besuchende Insekten’ (The application of Darwinian theory to flowers and flower-visiting insects; H. Müller 1869).
3
Müller had earlier studied the adaptation of Syrphidae (hoverfly) mouthparts to various sizes of pollen (see Correspondence vol. 15, letter from Hermann Müller, 23 October 1867). He found that different species possessed specialised channels adapted to different sizes of pollen.
4
Müller had noted that several flowers opened only at night; these were never visited by diurnal species like bees or flies but only by butterflies and especially moths (H. Müller 1869, pp. 64–5).
5
The order Diptera comprises true flies and midges; Hymenoptera are bees, wasps and ants.
6
In his letter to Müller of 16 August [1867] (this volume, Supplement), CD noted that he had only ever seen wasps visiting Epipactis latifolia (a synonym of E. helleborine, broad-leaved helleborine).
7
CD received a specimen of Angraecum sesquipedale (comet orchid) in January 1862 and was astounded by the length of its nectary (see Correspondence vol. 10, letter to J. D. Hooker, 25 [and 26] January [1862]). In Orchids, p. 198, CD concluded: ‘in Madagascar there must be moths with probosces capable of extension to a length of between ten and eleven inches!’
8
CD probably refers to François Jules Pictet de la Rive’s Traité de paléontologie, ou histoire naturelle des animaux fossiles considérés dans leurs rapports zoologiques et géologiques (Treatise on palaeontology, or natural history of fossil animals considered in their zoological and geological relationships; Pictet de la Rive 1853–7).
9
See Origin 4th ed., pp. 239–40.

To Hermann Müller1   14 March 1870

Down, Beckenham, Kent

March 14. 1870.

My dear Sir

I think you have set yourself a new, very interesting and difficult line of research.2 As far as I know, no one has carefully observed the structure of insects in relation to flowers, although so many have now attended to the converse relation. As I imagine few or no insects are adapted to suck the nectar or gather the pollen of any single family of plants, such striking adaptations can hardly, I presume, be expected in insects as in flowers.—3 … The importance of butterflies, who do not consume pollen, for flowers never occurred to me, and your considerations explain the enormous development of nocturnal species.4 It seems very odd to me, that there should be no nocturnal nectar-drinking Diptera or Hymenoptera.5 Has anyone investigated the stomach contents of bats? Based on humble bees and honeybees, who often visit various species, and following the example of wasps and Epipactis latifolia, I cannot help but think that the taste of nectar must influence the visits of butterflies much more than the structure of the flower.6 Would it be very difficult to determine the relationship of flowers occurring in Germany with such long nectaries or such long corolla tubes, that could only be exploited by butterflies? The explanation that I suggested in my orchid book for the length of the nectary in Angraecum, can, I suspect, be extended to other cases.7 You must, I think, using Pictet’s or other works, determine the earliest geological formations, in which the various orders of insects have been traced.8 There is much truth, I believe, in what I concluded in a later edition of “Origin of Species”, that before insects appeared, plants were not adorned with ornamental flowers.9 I fairly doubt, that any connection exists between the brilliant colours of butterflies, their floral visits, and sexual selection, since the sexes vary in colour so frequently throughout the whole animal kingdom. …

Yours very sincerely | Ch. Darwin

Copy incomplete

1
This letter was previously published in Correspondence vol. 18, with only the English text; the German translation of the rest of the letter has been added from Krause 1884. For a transcription of the German of the printed source, see Transcript.
2
See Correspondence vol. 18, letter from Hermann Müller, 8 March 1870. Müller had sent CD a copy of his paper ‘Die Anwendung der Darwin’schen Lehre auf Blumen und blumen-besuchende Insekten’ (The application of Darwinian theory to flowers and flower-visiting insects; H. Müller 1869).
3
Müller had earlier studied the adaptation of Syrphidae (hoverfly) mouthparts to various sizes of pollen (see Correspondence vol. 15, letter from Hermann Müller, 23 October 1867). He found that different species possessed specialised channels adapted to different sizes of pollen.
4
Müller had noted that several flowers opened only at night; these were never visited by diurnal species like bees or flies but only by butterflies and especially moths (H. Müller 1869, pp. 64–5).
5
The order Diptera comprises true flies and midges; Hymenoptera are bees, wasps and ants.
6
In his letter to Müller of 16 August [1867] (this volume, Supplement), CD noted that he had only ever seen wasps visiting Epipactis latifolia (a synonym of E. helleborine, broad-leaved helleborine).
7
CD received a specimen of Angraecum sesquipedale (comet orchid) in January 1862 and was astounded by the length of its nectary (see Correspondence vol. 10, letter to J. D. Hooker, 25 [and 26] January [1862]). In Orchids, p. 198, CD concluded: ‘in Madagascar there must be moths with probosces capable of extension to a length of between ten and eleven inches!’
8
CD probably refers to François Jules Pictet de la Rive’s Traité de paléontologie, ou histoire naturelle des animaux fossiles considérés dans leurs rapports zoologiques et géologiques (Treatise on palaeontology, or natural history of fossil animals considered in their zoological and geological relationships; Pictet de la Rive 1853–7).
9
See Origin 4th ed., pp. 239–40.

Please cite as “DCP-LETT-7131,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-7131