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Darwin Correspondence Project

From J. A. Harker   11 November 1878

17 Southgate Street, | Gloucester

11 Novr. 1878

To Charles Darwin Esq.

Dear Sir,

For the past four summers I have devoted some time to the examination and study of Ophrys apifera; in part attracted by the phenomena presented by its form and mode of fertilization as described in your “Fertilization of Orchids”.1 In one or two of my observations you may perhaps be interested should they prove new to you.

In 1877, from a handful of Bee Orchids gathered in a damp plantation near the banks of a brook, I remarked two specimens in which the two lowest flowers were expanded, but the lower lobe of the labellum with the lateral processes was entirely absent; presenting the appearance of being cut clean off by some sharp instrument. The edges of the remaining upper portion of the labellum were not torn or frayed, but were dry and shrivelled looking. The idea at once suggested itself that it was a malformation, but on keeping the plants in water for a few days the remaining buds opened disclosing normal labella.

The suggestion then was that the labellum in the lower flowers had been cut off, but by what means?

Hesitating to speculate on such small data I waited till 1878, when I renewed with zeal my search for every Bee Orchis to be found. Again and in nearly the same spot I found a plant with one of its flowers similarly treated, this time the 3rd. flower from the lowest. It was thus evident that the phenomenon had not been an isolated one in 1877, though out of more than 1000 plants examined only five instances of its occurrance were noted and of those two occurred on the same plant. The appearances presented by the edges of the remaining portion of the labellum so clearly suggesting a cut, I tried to imitate the act with a pair of sharp-pointed scissors; by holding the points of the scissors in front of a flower, and directing them down & forwards at an angle of 75o or so with the ground, and snipping off the labellum a fair imitation was obtained.

No small mammal, bird or reptile, mistaking the labellum for an insect, could have made such a cut, by snapping at the flower, but it suggests itself that it would be just what would result, if a large dragon fly, (of which by the way there are generally several at the spot) had pounced on an imaginary fly, and severed its body from its thorax with its powerful mandibles. I do not know of any other group of British Insect which could effect this.

Although O. apifera as pointed out in your book does not resemble any British Hymenopterous insect, yet with its bright purple reflexed sepals, and its labellum pushed out so prominently, it bears a very close resemblance to a flower in front of which a Dipteron of the genus Bombilius is hovering, thus representing both insect visiting & flowers visited.2 Accustomed to collect Diptera I have more than once been for an instant deceived by it.

If a large Æschna3 were so striking at the labellum of apifera mistaking it for a Bombilius, I think it would carry away the pollen masses, and if (a large if I know) we are justified in supposing that the two flowers on the plant described had been so visited, it does not seem a greater step to imagine that the most Dipteron-like Bee Orchids may have been or are cross-fertilized in this manner, or to suppose that at a time when dragon flies were certainly more numerous than now, its resemblance to a Bombilius would be highly useful to the plant in tending to favour occasional cross fertilization.

Ophrys apifera is mainly self fertilizing, but I believe there is good reason to think that it is a species which is either dying out, or is in process of change to something else. For my experience scarcely bears out this extract from “Fertilization of Orchids”—

“It is however remarkable on this view that none of the parts in question show any tendency to abortion—the flowers are still conspicuous”—4

On the contrary I have been impressed with the fact that abortion is the rule rather than the exception. On one day in July I examined 150 plants in flower and in quite 60 per cent the labellum was malformed in one way or another—one or other of the lateral lobes was imperfect, or inclined the reverse way   sometimes the whole side aborted, the terminal lobe shrunken or twisted, and in a large proportion the dispersion of the colour and markings was asymetrical.

Furthermore a friend brought me a specimen which developed 4 flowers the labellum of all of which were of a pale greenish white without trace of yellow or brown marking; and two other plants precisely similar were gathered in the same spot; that is within a few yards, one of the other.

One other fact regarding the habit of A. apifera is not generally noticed in our Floras—it appears to grow most luxuriantly in damp woods. In this part of the Country it is abundant everywhere from the banks of the estuary to the summits of our dry oolitic hills, but the largest specimens with best formed flowers are undoubtedly to be met with in woods & plantations— I have never seen any insect of any kind visiting its flowers, though I have sometimes fancied that bees hung for an instant in their flight when passing it, as if doubtful about it.

Thanking that these few observations might perhaps be of interest, in directing the attention of some of your correspondents who may be able to observe the Ophrydeæ in their head quarters, I have ventured to offer them to you. I need hardly say that I shall return to their consideration when the Orchis flowers next year with great attention and shall endeavour to bring home to the Dragon flies the act for which my suspicions have fixed on them as perpetuators.

I am, | Your obliged & obedt Sevt. | Allen Harker

Footnotes

CD discussed the self-fertilising Ophrys apifera (bee orchid) in Orchids 2d ed., pp. 52–9.
See Orchids 2d ed., p. 56. Bombylius (bee fly) is a genus in the order Diptera.
Aeshna is the genus of hawker or mosaic darner dragonflies in the order Odonata; they are the largest dragonflies in Britain.

Bibliography

Orchids 2d ed.: The various contrivances by which orchids are fertilised by insects. By Charles Darwin. 2d edition, revised. London: John Murray. 1877.

Summary

Has observed rare instances of Ophrys apifera with "cut labellum". Suggests it was done by large dragonfly mistaking the flower for a fly visiting a flower. Stimulated to study Ophrys by Orchids.

Letter details

Letter no.
DCP-LETT-11741
From
James Allen (Allen) Harker
To
Charles Robert Darwin
Sent from
Gloucester
Source of text
DAR 166: 101
Physical description
7pp

Please cite as

Darwin Correspondence Project, “Letter no. 11741,” accessed on 5 March 2021, https://www.darwinproject.ac.uk/letter/DCP-LETT-11741.xml

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