Note 4 — Chapter XXIII

Among these few insects, I was surprised to find a small Aphodius (nov. spec.) and an Oryctes, both extremely common under dung. When the island was discovered it certainly possessed no quadruped, excepting perhaps a mouse; it becomes, therefore, a difficult point to ascertain, whether these stercovorous insects have since been imported by accident, or if aborigines, on what food they formerly subsisted. On the banks of the Plata, where, from the vast number of cattle and horses, the fine plains of turf are richly manured, it is vain to seek the many kinds of dung-feeding beetles, which occur so abundantly in Europe. I observed only an Oryctes (the insects of this genus in Europe generally feed on decayed vegetable matter) and two species of Phanæus, common in such situations. On the opposite side of the Cordillera in Chiloe, another species of this genus is exceedingly abundant, and it buries the dung of cattle in large earthen balls beneath the ground. There is reason to believe that the genus Phanæus, before the introduction of cattle acted as scavengers to man. In Great Britain those beetles, which find support in the matter, which has already contributed towards the life of other and larger animals, are so numerous, that I suppose there are at least one hundred different kinds. Considering this, and observing what a quantity of food is thus lost on the plains of La Plata, I imagined I saw an instance where man had disturbed that chain, by which so many animals are linked together in their native country. To this view, however, Van Diemen’s Land offers an exception (in the same manner as St. Helena does in a much lesser degree), for I found there four species of Onthophagus, two of Aphodius, and one of a third genus, very abundant under the dung of cows; yet these latter animals had then been introduced only thirty-three years. Previously to that time, the Kangaroo and some other small animals were the only quadrupeds; and their dung is of a very different quality from that of their successors introduced by man. In England the greater number of stercovorous beetles are confined in their appetites; that is, they do not depend indifferently on any quadruped for the means of subsistence. The change, therefore, in habits, which must have taken place in Van Diemen’s Land, is the more remarkable.—I am indebted to the Rev. F. W. Hope, who, I hope, will permit me to call him my master in Entomology, for information respecting the foregoing, and other insects.