Page:The New International Encyclopædia 1st ed. v. 10.djvu/751

* INSECTICIDE. 663 INSECT POWDER. soap). Since kerosene can rarely be applied with safety to growing plants, it is emulsilied by mixing and churning violently two gallons of kerosene with a solution of eight ounces of hard soap in one gallon of hot water, and diluted when needed for use with from five to ten times as much water. E.periments have been made with pumps that mi.K kerosene and water in •definite proportions as they are drawn from two respective tanks by the one piston-stroke. If successful, such jjumps will save mucli dis- agreeable labor. Whale-oil soap is applied as a solution of one pound in one to ten gallons of water. Certain insects, notably the San Jose scale, a serious pest of woody plants, and the ■thineh-bug, an equally troublesome pest of <'ereals. have been experimented upon in a unique way; diseases were spread among them, in the first case by means of infected water sprayed npon them; in t)ie latter by infected insects. Kesults were not particularly satisfactory in either case. Not so in the case of the cottony cushion scale, a pest on citrus trees in California. A ladybird beetle, imported from Australia, in a few years extirpated the pest. This is perhaps the most notable instance of hian's utilizing a natural control and making it an insecticide in the narrow sense. See Ladybird. Certain species of insects (clothes-moths and ^ranaiy insects) may be best destro3'ed by sufTo- •cation in the fumes of carbon disulphide evaporated in shallow dishes placed at the top •of the air-tiglit receptacle containing the ma- terial to be fumigated. An ounce to 50 or 75 <aibic feet is the usual proportion, the box being kept closed for twenty-four hours or more. Since the fumes of carbon disulphide are very explosive, lights must be kept away. Hydrocyanic-acid gas is also largely used to suffocate insects, espe- cially certain greenhouse and nursery stock pests, 3ind the groups known as scale-insects, notablj- the San Josu scale. The gas is generated from potassium cyanide (08-0'J per cent, pure) in a mixture of sulphuric acid and water, the propor- tions being 1 oz. cyanide of potassium. 2% oz. ■water. 1% oz. sulphuric acid for each 100 cubic feet for nurserv stock operated upon; 125 cubic ieet for trees, granaries, flour-mills, and rooms; and 250 cubic feet for greenhouses. The usvial exposures are from half an hour to an hour for plants and trees, according to whether they are j;rowing or dormant, and 12 to 24 hours for rooms, etc. Since both the gas and the salt from which it is made are virulent poisons, no person who is not both careful and competent should •employ them. The insects that attack domestic animals and man. though individually serious pests, form a numerically insignificant group when compared to the great group of plant-feeding species. Hogs and sheep may lie freed from lice by greasy mixtures and tobacco or carbolic washes; in- fested horses and cattle should be thoroughly curried once a week until the animals are free, the brush l>eing dipped frequently in kerosene emulsion diluied with five or six parts of water. Similar remedies apply to the related parasites of the human subject, vaseline or lard being sub- stituted for the kerosene emulsion. For the body-louse and the crab-louse hard boiling of infested clothes for half an hour or longer is <'ssential. siuce the eggs are very resistant. Poul- try may be kept free from lice by a liberal supply of fine dust, and their houses by fumigation with carbon disulphide or hydroeyanic-acid gas once a week and the frequent application of kerosene and whitewash. Carbolic soap is a standard insecti- cide against fleas in pet animals. With animals of all I'Cinds, however, cleanliness is a great safe- guard, since the insects which arrive first are de- stroyed before they have a chance to breed. IN'SECTIV'ORA (Xeo-Lat. noni. pi., from Lat. iiiSLCliim, insect + vorare, to devour). An order of placental mammals, containing about 250 species, arranged in two suborders — ( 1 ) true Insectivora; (2) Dermoptera. The former includes the hedgehogs, tenrecs, moles, and mole- like animals, elephant shrews, true shrews, and the like, and the latter the 'Hying lemur' (Ga- leopithecus). None of the Insectivora are of large size; most of them are small timid crea- tures, generally nocturnal in their habits, and useful in the economy of nature chielly in pre- venting the undue increase of worm and insect pests. Although many of them are not exclu- sively insectivorous, all of them have the sum- mits of the molar teeth beset with small conical tubercles, well adapted for breaking up the hard coverings of insect prey. Their dentition is characterized by a' distinct tendency toward suppression of the milk dentition, but otherwise is variable. The legs are short, and the feet of most of them are plantigrade. The cerebrum is small and smooth, and does not cover the cere- bellum. The order is regarded as one of the inferior, and among the most ancient, of the mammalian groups; and, with the exception of a single genus (Solenodon, of Cuba), they are now confined to the Northern Hemisphere, and to South Africa and INIadagascar, i.e. to Artogfca. The most recent and advanced review of the order is Dobson, A Monograph of the Inscctifora (Lon- don. 188G-00). IN'SECTIV'OROtrS PLANTS. Plants that catch and assimilate insects as part of their food. See Carnivorous Plants. INSECT POWDEB, Pyrethrum. Buhach, Dalmatian or Persian Lnsect Powder. A brownish-yellow powder obtained by grinding the dried flower-heads of two species of Chrysanthe- mum (Pyrethrum), a genus of plants of the natural order Composita;. The species employed are Vhrijsanthemum coccineum. popularly known as Pyrethrum roseum. and often grown as an ornaiiiental summer-bedding plant, and Chry- siinlhemum eineraricefolium, also called Piirc- Ihriim cinernriwfolium. From the flowers of the former, a Persian species, is made Dalmatian or Persian insect powder — better known in Eu- rope than in America; from those of the latter, a Caucasian species, extensively cultivated in California, is manufactured the insect powder buhach and pyrethrum, common in the I'nited States. When fresh the powder made from each species seems to be equally effective: but since the volatile oil, upon which their effectiveness depends, is lost with age and also by exposure to air and heat, the California product is con- sidered with more favor in America than the imported powder. Chri/nanthemum cineraria:- folium is preferred in California, because its flowers may be gathered at approximately one time, whereas Chrjixniithciniim coceiiwiim has an extended period of bloom. The volatile oil acts upon insects by asphyxiation; upon man and