A biology of the British Hemiptera-Heteroptera / by Edward A. Butler.

  • Butler, Edward A. (Edward Albert), 1845-
Date:
1923
Catalogue details

Licence: Public Domain Mark

Credit: A biology of the British Hemiptera-Heteroptera / by Edward A. Butler. Source: Wellcome Collection.

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    communication with their fellows of the Continent during all the centuries and millenniums that have elapsed since the sea broke the last links of connexion and formed the Straits of Dover, very little differentiation has taken place between the insular and the continental forms of the same species. It follows, therefore, that if any changes have been produced in the insular Hemiptera by natural causes throughout all those ages, they must, in the main, have been balanced on the Continent by similar changes due to the operation of like causes. Such trifling differences as do exist are to be met with chiefly amongst the Capsidae, and the most noteworthy example is that of Calocoris sexguttatus ; our specimens are of a form and coloration which, according to Reuter, is not found on the Continent, while the usual continental form does not occur with us. Another example is that of Camp- tozygum pinastri, which, with us, is usually much paler than the continental form, and Dr. Reuter was much struck with this fact on his first visit to Scotland. The black variety of Stenodema laevigcitum, again, which is rare with us, is not recorded at all from the Continent, though a similar melanic form of a closely allied species, S. virens, has occurred there ; and finally the range of variation in most species is usually wider on the Continent than with us. Six species have been recorded from the British Isles only, viz. Myr- medobia inconspicua, Globiceps ater, Conostethus brevis, Corixa saundersi, C. boldi, and C, caledonica ; but two of these, Globiceps ater and Corixa boldi, are known by single specimens only, taken very many years ago, and it seems probable that these are not true species, but mere aberrations of some allied forms. The variety Psallus variabilis, var. whitei, also is recorded from Britain only. Judging from the analogy of other groups of animals, there can be little doubt that the Hemipterous fauna which peopled the country after the last Glacial Period, and from which our present fauna has been derived, must have been more extensive than the present one, and that many species must have been exterminated. For an island, Great Britain covers a large area, and the geographical and climatic conditions are exceedingly diversified ; every kind of soil is present, and the vegetable products are almost equally varied ; geologically, it is well known, oux island is a kind of epitome of Europe; hence the con¬ ditions are not such as would produce to any marked degree what on a small island is known as an insular fauna. Apart from the few instances quoted above, there is very little to distinguish our British from the continental Hemiptera, and the chief result of the separation of these islands is to be seen in the reduction of the number of species. Nor does the long-established cultivation of the country seem to have made much difference, and this is only what was to be expected, as the con¬ ditions on that part of the Continent nearest us have been similar. Perhaps
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