Art. XXV.—On some Mites parasitic on Beetles and Woodlice. By W. M. Maskell [Read before the Wellington Philosophical Society, 26th October, 1892.] Parasites, as Thackeray says, exist always; and there is perhaps no portion of the great animal kingdom (excepting man) which exhibits the truth of this saying more fully than the various tribes and families of insects, and of the Crustacea. These organisms, which are themselves commonly engaged in preying upon their fellow-creatures, are subject to an infinite variety of hostile attacks from beings smaller than they are, and their lives (perhaps fortunately for the rest of creation) must be by no means happy ones. It would be a very useful thing if the study of the different insect parasites in New Zealand were seriously undertaken, and it is to be hoped that some day, when a proper Agricultural Department exists here, this will be done. Meanwhile every contribution to knowledge is valuable, and the following note is offered as a small instalment. Parasites upon the smaller forms of animal life, such as insects or Crustacea, may be of many kinds. Some are themselves insects, such as the minute Hymenoptera which prey upon the so-called “blights”; others are Entozoa, internal parasites preying upon the very intestines of their hosts; others, again, belong to the great order Arachnoidea, which includes not only the spiders but also the different mites. Mites feed on both animal and vegetable matter. Some are harmless, some injurious, some useful, some even murderously noxious. In the sheep-scab and human itch we have examples of abominable nuisances; in the almost invisible little animal which swarms often in cabinets and boxes we have an annoying and destructive enemy; in the tree- or beetle-mites we have frequently very useful scavengers; in sugar or in biscuit, mites are both injurious and offensive; while we consider that the presence of mites is not only harmless but even necessary to the proper ripeness and flavour of certain kinds of cheese which are inferior without them. Amongst all these varieties of mites there is one family which has for its special object the preying upon some species of animals which are themselves enemies to man; and two of these I am introducing to you this evening. If anybody here present has occupied himself with farming he will be only too well acquainted with what are known as “wireworms”; while anybody who grows flowers in pots has had troubles with the little animals called “woodlice.” The mites which I now exhibit, none of which

are larger than a very small pin's head, devour and annoy these two animals, and are therefore friends of man. The great order Acarina, or mites generally, includes many subdivisions, ofwhich one is that of the Gamasinœ, or miteparasites; and this, again, contains several genera, of which one has received the name of Uropoda. It is the habit of Uropoda to attach itself (not singly, but in clusters of as many as can climb on) to the back of some insect or animal, preferably a more or less subterranean one, and there to live, move, and have its being. A glance at the specimen which I exhibit will show an unfortunate little beetle so completely covered with numbers of mites that it is not easy to make out its body. The specimen and its parasites are now dead, but when they were alive it seemed not easy to understand how so many mites could hang on to so small an object; and it is only by close observation and by trying to pull some of the mites off that one discovers a very tine silky hair fastened by one end to the beetle and by the other to the mite, which effectually prevents the latter from falling off, and, indeed, fastens it on rather firmly. Naturalists, I believe, are not yet fully acquainted with the nature of this hair, or cord, though Mr. Andrew Murray says that the mite can detach itself if it pleases. Whether this is so or not it seems clear that the victim has no such power; and the condition of an insect or of a woodlouse under these circumstances cannot be at all enviable. Uropoda may sometimes, in wet weather, be found adhering to stones instead of to animals; but it would seem that the congenial home of these mites is the skin of some other small animal. On the stages of the two microscopes on the table are shown specimens of mites taken in the one case from a woodlouse (Oniscus sp.), in the other from a small click-beetle (Elater), the full-grown form of the “wireworm.” It will be at once seen that both are yellowish-brown, oval, flattish, and hard; and that they have the eight feet and the mouth-organs characteristic of the true mites. Possibly very close observation might discover minute differences in the arrangement of the bristly hairs visible on the surface of the body, and these differences might suggest the separation of the specimens into two species. I do not, however, see any necessity for this, nor shall I attempt to distinguish these animals from the European mites which are known to have precisely similar habits. The present note has therefore been put forward only to record the existence in New Zealand of these minute parasites, which, although apparently not very common, are doing something to help man in his warfare against the enemies to cultivation.

Assuming, then, that these mites are identical with, or very slight variations from, the European form, they must be recorded as follows:— Order Arachnoidea. Fam. Gamasinæ. Sub-fam. Gamasid æ. Gen. Uropoda, Latreille. Species Uropoda vegetans, De Geer. Minute mites, parasitic upon Coleoptera (Elater and Crustacea (Oniscus) in New Zealand. Form flattish, subcircular; colour yellowish-brown; attached in clusters by fine threads to the host. Characters generally of Gamasinœ: Eyes none, mandibles chelate, feet eight, each with a double claw and a minute caruncle or pad. Localities, up to the present: Christchurch (on Oniscus); Wellington (on Elater). The Wellington specimens were sent to the Museum lately by Colonel Humfrey, of the Hutt.