The Pupa. The possession of eight legs distinguishes the pupa easily from the larva. The extra pair are placed behind the others. After the metamorphosis, the pupa takes up its position on the stalks of herbage, just as the larva had done, for another chance of attachment to a host. But whereas adult grass ticks seem to confine themselves mostly to sheep, cattle, and deer, the larvæ and pupæ attach themselves very readily to various hosts, such as horses, dogs, and even human beings. After about four days the pupa is again replete with blood, black and opaque, and again drops to the ground to undergo its second and final change.
Adults. On reaching the adult age, both males and females again wait on herbage for a passing host. At this time, as well as after distension of the female on the host, an action which appears to be sexual intercourse freely takes place, even in confinement. On the host the females gradually distend (Fig. 202), and in the course of so doing vary much in colour and appearance. When fully replete, the female Ixodes reduvius becomes globular and black. One taken in this condition on April 15th commenced to lay on May 12th, and a few others taken at the same time commenced shortly afterwards.
Grass ticks never remain on the host to undergo metamorphosis or to lay eggs. They must therefore during their cycle of existence contrive to find a fresh host no fewer than three times.
In an article published in the Transactions of the Highland and Ag. Soc. for 1902 Mr. Wheeler draws attention to the close points of resemblance between louping-ill, Texas fever, tsetse fly disease, surra, heart-water, yellow fever, and malaria.
In the article previously referred to he summarises his conclusions as follows:—
One species only of tick, Ixodes reduvius, commonly known as the grass tick, has been found to carry the louping-ill bacillus to the sheep. It is easily recognised by the red body of the young females, the legs, shield, etc., being dark brown.
It lays its eggs, and undergoes its metamorphoses, in coarse herbage, and after each change seeks a fresh “host” on which to distend itself to a large size by suction of blood.
Fig. 203.—Female, under size.
