GEOGRAPHY OF CENTRAL FLORIDA 233

etc. Being only about the size of a pin-point, it is not easy to determine its natural habitats, but it evidently frequents places that are rarely burned, like hammocks, swamps, and roadside- shrubbery, and is scarce in pine lands. It is annoying but not dangerous, and its pernicious activities are chiefly confined to the warmer half of the year. The instinct that leads it to burrow into human skin is a suicidal. one, for there' is very little chance of such an individual having any descendants to inherit the same tastes.*
 There are several species of ticks, with habits similar to those of the red bug, but being larger they are less abundant and more easily dealt with. The cattle-tick which infests the ranges and pastures has been viewed with alarm by stock-raisers in recent years, and a campaign for its extermination is now under way, with good prospects of success.'
 Miscellaneous invertebrates. The scorpion, which looks just like one of the pictures among the signs of the zodiac in old-fashioned almanacs, is more or less common in South Florida, but the writer has never seen but one in central Florida, that in Lake County in 1909.
 Earthworms, which abound in clayey and loamy soils in most parts of the civilized world, and are an important factor in maintaining the fertility of such soils, are scarce in the sand of peninsular Florida, but there are said to be a few native species in the humus of our hammocks, and very likely some of the European species occur in gardens.
 Of the many mollusks, terrestrial and aquatic, univalves and bivalves, living and fossil, only the oyster need be mentioned here. It is common in salt water (see fig. 3), and is shipped from Cedar Keys and elsewhere. Its shells have been used extensively on roads near the coast, as stated in the chapter on roads, farther on, but they are now being gradually superseded by brick and asphalt.
 Sponges grow on the rocky bottom of the shallow waters along the Gulf hammock coast, and Tarpon Springs is a great center for the sponge industry, which is carried on by Greeks. A few are also brought in to Cedar Keys.

 *See Farmers' Bulletin 671 of the U. S. Department of Agriculture, 1915. Also N. Banks, Proc. U. S. Nat. Mus. 28:30-33. 1904.
 tFor notes on ticks see Banks, I. c.. pp. 42-49.