5o6 THE POPULAR SCIENCE MONTHLY. 



tropics, and these exotic tick-mites are not infrequently imported on 

 plants, and in the moss and sphagnum which horticulturists use in 

 packing their wares. The habits of this group are somewhat anoma- 

 lous ; at first they are unquestionably herbivorous, but they greedily 

 avail themselves of every opportunity of sucking blood instead of sap. 

 No special adaptation is needed for this, as the sucking-apparatus is 

 suited to both the liquid blood and the juice of plants, and is similar 

 to that of all suctorial insects, which some use on plants, some on ani- 

 mals, and some on both. Of the immense swarms of ticks, gnats, mos- 

 quitoes, bed-bugs, etc., the majority pr^ably never taste animal food 

 at all, although so greedy for it when it comes in their way. 



The sub-family, Acaridce, is divided into two sections : the cheese- 

 mites and their allies, and the itch-mites with their relatives. The 

 first section produces a number of vegetable-feeders ; several species 

 are found on the scales of some species of Liliacece, principally hya- 

 cinths, and on dahlia-roots, cyclamen, potatoes, mushrooms, etc. ; these 

 occasionally cause itching and irritation to those handling them. The 

 smallest species of this group, T'yroglyx>hus entoinophagus, is a pest 

 too well known to entomologists, upon whose collections it preys. It 

 lives chiefly in the inside of the insects which it attacks, gnawing the 

 soft parts of their bodies, and destroying the ligaments which liold 

 the articulations together, allowing them to fall apart. 



Edible mushrooms, especially the cultivated sorts, are often at- 

 tacked by a moist black rot, which, until lately, has been regarded as 

 spontaneous. But it has been shown that it is caused, or at least 

 aided, by a species of mite remarkable for fecundity. The activity of 

 their agency in this decomposition is shown by the fact that mushrooms 

 on which they have been placed become, in forty-eight hours, a black, 

 putrescent mass, on which myriads of these creatures swarm ; while 

 other mushrooms subjected to the same conditions, except the inocu- 

 lation, dry up, and take from eight days to a fortnight to decompose. 

 The presence of mites in great numbers on some of the common arti- 

 cles of food is well known. These are chiefly the cheese-mites, which 

 are characterized by a soft, smooth, fleshy, whitish body, with gener- 

 ally a single claw, surrounded by a vesicle or fine sucker, like a sieve. 

 T. siro (Fig. 5) is the principal mite which commits ravages upon 

 cheese, living upon all kinds when a little decayed, and especially the 

 harder parts. They hibernate during winter, crowded in heaps in 

 chinks and hollows in the cheese ; but with warm weather their ac- 

 tivity begins, and they gnaw away, reducing the cheese to powder. 

 This powder is composed of excrement in little grayish balls, eggs, 

 egg-shells, larvae, cast skins, perfect mites, fragments of cheese, and 

 numerous spores of microscopic fungi. A mite-tainted cheese is not 

 objected to by epicures, and the creatures ai-e sometimes introduced 

 to give a premature ripeness ; but, if left to work unchecked, they 

 will spoil a cheese very soon. 



