LAND LEECHES.
One circumstance regarding these land leeches is remarkable and unexplained; they are helpless without moisture, and in the hills where they abound at all other times, they entirely disappear during long droughts;—yet re-appear instantaneously on the very first fall of rain; and in spots previously parched, where not one was visible an hour before; a single shower is sufficient to reproduce them in thousands, lurking beneath the decaying leaves, or striding with rapid movements across the gravel. Whence do they re-appear? Do they, too, take a "summer sleep," like the reptiles, molluscs, and tank fishes, or may they be, like the Rotifera, dried up and preserved for an indefinite period, resuming their vital activity on the mere recurrence of moisture?
Besides the medicinal leech, a species of which[1] is found in Ceylon, nearly double the size of the European one, and with a prodigious faculty of engorging blood, there is another pest in the low country, which is a source of considerable annoyance, and often of loss, to the husbandman. This is the cattle leech[2], which infests the stagnant pools, chiefly in the alluvial lands around the base of the mountain zone, to which the cattle resort by day, and the wild animals by night, to quench their thirst and to bathe. Lurking amongst the rank vegetation which fringes these deep pools, and hid by the broad leaves, or concealed among the stems and roots covered by the water, there are quantities of these pests in wait to attack the animals that approach them. Their natural food consists of the juices of lumbrici and other invertebrata; but they generally avail themselves of the opportunity afforded by the dipping of the muzzles of the animals into the water to fasten on their nostrils, and by degrees to make their way to the deeper recesses of the nasal passages, and the mucous membranes of the throat and gullet. As many as a dozen have been found attached to the epiglottis and pharynx of a bullock, producing such irritation and submucous effusion that death has eventually ensued; and so tenacious are the leeches that even after death they retain their hold for some hours.[3]
DORSAL and VENTRAL.
1: Hirudo sanguisorba. The paddifield leech of Ceylon, used for surgical purposes, has the dorsal surface of blackish olive, with several longitudinal striæ, more or less defined; the crenated margin yellow. The ventral surface is fulvous, bordered laterally with olive; the extreme margin yellow. The eyes are ranged as in the common medicinal leech of Europe; the four anterior ones rather larger than the others. The teeth are 140 in each series, appearing as a single row; in size diminishing gradually from one end, very close set, and about half the width of a tooth apart. When of full size, these leeches are about two inches long, but reaching to six inches when extended. Mr. Thwaites, to whom I am indebted for these particulars, adds that he saw in a tank at Colonna Corle leeches which appeared to him flatter and of a darker colour than those described above, but that he had not an opportunity of examining them particularly.
Mr. Thwaites states that there is a smaller tank leech of an olive-green colour, with some indistinct longitudinal striæ on the upper surface; the crenated margin of a pale yellowish-green; ocelli as in the paddi-field leech. Length, one inch at rest, three inches when extended.
Mr. E. LAYARD informs us, Mag. Nat. Hist. p. 225, 1853, that a bubbling spring at the village of Tonniotoo, three miles S.W. of Moeletivoe, supplies most of the leeches used in the island. Those in use at Colombo are obtained in the immediate vicinity.
2: Hæmopsis paludum. In size the cattle leech of Ceylon is somewhat larger than the medicinal leech of Europe; in colour it is of a uniform brown without bands, unless a rufous margin may be so considered. It has dark striæ. The body is somewhat rounded, flat when swimming, and composed of rather more than ninety rings. The greatest dimension is a little in advance of the anal sucker; the body thence tapers to the other extremity, which ends in an upper lip projecting considerably beyond the mouth. The eyes, ten in number, are disposed as in the common leech. The mouth is oval, the biting apparatus with difficulty seen, and the teeth not very numerous. The bite is so little acute that the moment of attachment and of division of the membrane is scarcely perceived by the sufferer from its attack.