90 THE EEPOET OF THE No. 36 



checking the spread of locusts, as ahuost every locust upon which one is found 

 appears to be feeble and sickly. Another species, Celaenopsis latus, attacks the 

 larva of Passalus cornutus, and still others, attacking garden pests are found on 

 the larva of Lachnosterna, Attacking fruit tree pests may be mentioned Hem- 

 isarcoptes malus on San Jose Scale and Oyster Shell Bark Louse; RJujnchoIophus 

 ^p. feeding on San Jose and New York Plum scale; Cheyhtes pijriformis on the 

 larva of the Codling Moth. On forest tree insects we have a species destroying 

 the Cottony Maple Scale and another species attacking the Maple Plant Louse. 

 On household pests we have Histiostuma muscarum parasitic on the house-fly and 

 other species on mosquitoes. The mites themselves are largely kept in check by 

 predaceous and parasitic species belonging to this group. Sejus macro phyhis, found 

 in the Aspen Eriopliyes gall, and Gamasid species attacking Pear Leaf Blister 

 mite. Here we might also mention that a large number of the aquatic insects 

 are parasitized by Hydrachnids (water mites). Besides the species found prey- 

 ing upon insects there are a large number which attach themselves to the body of 

 the insect without causing any apparent harm or annoyance. Examples of these 

 are the following: 



Uropoda sp. on Eough Osmoderma, Ceramibycids, Skin Beetles, Tumhle Bugs, 

 Darkling Beetles, etc. ; and Macroclieles sp. on Carrion beetles, Silpha, and Horned 

 Passalus. 



As Parasites of Water Insects. 



The water beetles and bugs are mostly parasitized by a species Hydrachna 

 helostomae which attaches itself to the ventral surface of the Electric Light bug. 



As Parasites and Guests of Mollusks. 



A number of species of water mites have been collected from the gills and 

 attached to the bodies of bivalves but the identification of these have not yet been 

 completed. 



As Scavengers. 



As a means of elimination of waste materials, there is probably no more 

 effective agent than the mites. There is no kind of filth or decaying matter which 

 is not relished by some species or other of the Acarids. In manure, sewerage, 

 decaying vegetable matter, decaying animal matter and all forms of dirt, mitea 

 are to be found actively engaged. 



Of Manure. Samples of nearly all kinds of manure were used in the mite 

 machine, and in almost every case mites were obtained. Histlostoma ralida is a 

 common example in horse manure. 



Of Decaying Vegetable Matter. Decaying potatoes, mangels, turnips, 

 parsnips, carrots, kohl rabi, corn stubble, cabbage, lettuce, decaying leaves, humus 

 in the soil, sawdust, rotten stumps, fleshy fungi were all found to be hastened 

 through the stages of decomposition by these busy creatures. 



Of Decaying Animal Matter. Almost every particle of thrown-off material 

 from the animal body such as epidermal scales of birds and mammals, moulted 

 skins of insects, are readily consumed by some species of these scavengers. Bone, 

 horn, flesh and hair are also their foods, and it is next to impossible to find a 

 single bit of any of these substances without finding along with it certain kinds 

 of mites. 



Of Mineral Matter. Mites were found upon rock ancT stone in all cases 

 of weathering, in every little crevice where the wearings from the rock had lodged. 



