The Minor Horrors of War

by Sir A. E. Shipley

Ornithodorus moubata, sometimes known as the ‘tampan,’ occurs pretty often in South Africa, and was a cause of considerable trouble to our troops during the South African War. It lives normally in the shade of vegetation, but frequently invades the native huts. It is catholic in its taste and attacks most mammals, and it has a decided preference for men. In Uganda the natives frequently die from its bites—dying of so-called ‘tick-fever.’

Fig. 45.—Ornithodorus moubata. Female, gorged, seen in profile. (After Brumpt.)

I myself once assisted in identifying two ticks, in the nymph stage, taken in Cambridge from the ear of an American visitor to this country, who had been camping out in Arizona shortly before his arrival. This tick turned out to be a species of Ornithodorus megnini, which, as a rule, attacks the horse, the ass, and the ox about the ears. But it frequently attacks man, and is well known in the United States, infesting the ears of children. An allied species, O. turicata, proves fatal to fowls in the Southern States and in Mexico, and is very harmful to human beings. The chief harm that these ticks do is to transmit protozoal diseases to man and other animals.

A very few ticks are said to be parthenogenetic, but by far the greater part lay fertilised eggs, and lay them in considerable numbers; and the eggs are agglutinated together in solid little masses, by the sticky secretion of a cephalic gland, which opens below the rostrum. The eggs are small and elliptical, and are laid to the number of many thousands. The young tick, which is usually born with but three pairs of legs, hatches out in a few days if the weather be warm, or a few weeks should it prove cold. A certain amount of moisture must be present, or the eggs are apt to dry up. These masses of eggs are laid on the ground under herbs or grass, or on leaves.

Fig. 46.—Ixodes ricinus. The male is inserting its rostrum in the female genital duct before depositing its spermatophore. × 6. (From Brumpt.)

The issuing six-legged larvae, like the young of other animals, are very agile, climbing on to leaves and herbage. They passionately wait with their front legs eagerly stretching out for the passage of the host upon which they desire to settle. Of course, but one in ten thousand succeeds, and it is terrible to think of the amount of unsatisfied desire which must be going on in the tick world! The rest perish miserably. Those that do succeed attach themselves to the skin of the host, and thrust their rostrum and sucking-tube into the hole already prepared by the cutting chelicerae. They suck the blood, and when gorged fall to the earth, or in some cases remain on the host in a state of inertia or apparent syncope.

Soon, however, the gorged larva moults, and gives rise to the first nymph—an eight-legged creature. This affixes itself anew upon a host—either upon the same or another one—again gorges itself, and in all points resembles the adult, except from the fact that the sexual orifice has not yet appeared. After some days the first nymph moults, and then again remains either on the host or it falls to the ground. In some cases there are two successive nymph forms; but as a rule the first nymph gives rise by a second moult to the adult form, which again for the third time regains a host. The adults are now ripe for pairing, and the male having enlarged the orifice of the oviduct by inserting its rostrum, deposits therein a spermatophore or capsule full of spermatozoa. The female is often successively fertilised by several males.

In many cases the male dies after fertilisation. The female swells enormously when gorged, sometimes becoming as large as a filbert, or even a small walnut. These ticks are seldom parasites of one particular host, but attack many mammals indifferently. They have many natural enemies: amongst the most important of which are certain hemipterous insects whose female attacks the nymph of the Ixodes, and lays within the body of the tick a number of eggs which develop inside the nymph until they reach the adult stage, when they make their escape through an orifice, generally at the hind end, leaving behind them the dead body of their host. Three species of such Hemipterous insects are known to be parasitic on ticks: of these Ixodiphagus caucurtei is ubiquitous. It attacks all kinds of ticks, but especially Dermacentor venustus.