Fig. 422.
1. Parasite of Eagle; 2. Parasite of Vulture; 3. Parasite of Pigeon, Sarcoptes palumbinus. (The circles enclose each about life size.)
Two small and obscure groups of the mites and ticks have been associated with the latter, but for no better reason than that their affinities are unknown. The first of these are the Tardigrada, or bear animalcules, which comprise microscopical animals living in damp, sandy, and mossy places; the body is long and oval in shape, and possesses four pairs of bud-like unjointed appendages, each tipped with claws: the last pair of legs project from the hinder part of the body. The mouth is much subdued, and only a trace of jaws is found as a pair of stylets; there appear to be no organs of respiration or circulation, and, unlike what obtains in all true Arachnida, the sexes are united in each individual. These curious infusorial creatures have been found by myself in an infusion of cow manure.
Injurious Insects.—In describing some of the more interesting points in connection with insect life, I have only quite incidentally referred to the destructive habits of the larger number of insects and the ravages annually inflicted, chiefly by the smaller parasitical tribes, upon our cultivated crops of all kinds.
Here we have a wide field of research open to the microscopist, whose investigations must be carried out systematically, day by day, and for which a moderate power will effectually serve his purpose.
There are some ten or twelve species of injurious insects that attack the hop plant. By way of example, I will select one of the least known among them, the hop-flea, or beetle (Haltica concinna). This is sufficiently minute to require the aid of the microscope, and very closely resembles the turnip-flea proper, H. nemorum. Under the microscope the former will be seen to differ considerably. Its colour is brassy, whereas the colour of its congener is dusky or black, and its wing-cases are striped. They both have wonderful powers of jumping. H. concinna has a curious toothed formation of the tibia, with a set of spines, while the tibia of the turnip-flea is without any curve. It presents other points of difference. The hop-flea is, in fact, a winged beetle, and passes the winter in the perfect state under clods, tufts of grass, or weeds outside the hop-plantation, and here it lays its eggs. In the early spring the larvæ are hatched out as a little white maggot, which immediately makes its way to the hop-plant and burrows into the young leaves and feeds upon its tissues. Here we have an insect taken at random from among thousands of others of the most destructive kinds which annually destroy crops of enormous value to the nation.
Tuffen West, del. Edmund Evans.
Plate VII.