AuouiT I, iSSs-l 



THE TROPICAL AGRICULTUKIST, 



151 



IJ^ SECTS AND AGE.ICULTUKE. 



lu the primitive couclition of the couutry, as the white 

 mau found it, insects, doubtless, took their proper 

 place iu Nature's economy, and rarely preponderated in 

 any direction to the injui-y of the wild plants, scattered, 

 for the most part, sparsely throughout their range. 

 Harmony between organisms, in the sense of the widest 

 inter-relation and iuter-dependeiice, had resulted iu the 

 long course of ages. But civilised man violated .this 

 primitive harmony. His agriculture, which is essentially 

 the encouragement and cultivation, in large tracts of 

 one species of plant to the exclusion of otliers which he 

 denominates weeds, gave exceptional facilities for tho 

 multiplication of such insects as naturally fed on such 

 plants. In addition to this inevitable increase of species 

 thus encouraged, many others have been unwittingly 

 imported form other countries, chiefly through the in- 

 strumentality of commerce with those countries ; for it is 

 a most significant fact that the worst weeds and the 

 worst insect pests of American agriculture are importations 

 from Europe. Thus, iu addition to the undue increase in 

 our native species, as above noted, we have to contend 

 with these introduced foreigners, and it is no wonder 

 that Dr. Fitch declared America to be the land of 

 insects, for, as compared to Europe, we are truly bug- 

 ridden. As I have stated {Encydopcedia Americana, 

 " Agricultural Entomology") : — "The losses occasioned by 

 insects injurious to agricidtiu'e in the United States, 

 are, in the aggregate, enormous, and have been variously 

 estimated at from 300,000,000 dels, to 400,000,000 dels, 

 annually. It will never be possible to fully protect our 

 crops from the ravages of the many species that 

 injuriously affect them: but it is the aim of the 

 economic entomologist to prevent as much of the loss 

 as possible, and at the very least expense. To do so 

 eflectually the chief knowledge required is of an entomol- 

 ogical nature, i.e., the fuU life-history and habits of 

 the different species; and this implies a great deal of 

 close and accurate work in field and laboratory. By 

 means of it we leam which species are beneficial, and 

 which injurious; and the ability to distinguish between 

 friend and foe is of the first importance in coping with 

 the latter, for it is a nocorious fact that the farmer 

 often does more harm than good by destroymg 

 the former in his blind efforts to save his crops. 

 . . , The economic entomologist, to do effectual work, 

 must possess, not merely a knowledge of the particular 

 injurious species and its habits with which he wishes to 

 deal, but must study its relations to wild plants as well 

 as to the particular cultivated crops it affects. He 

 must also study it iu its relations to other animals. In- 

 deed, its whole en%'ironment must be considered, especi- 

 ally in connection with the farmer's wants, the natural 

 checks which surround it, and the methods of culture 

 that most affect it. The habits of buds, the nature 

 and development of minute parasitic organisms, such as 

 fungi, the bearing of meteorology, must all be considered, 

 and yet, with the knowledge that a study of all these 

 bearings implies, he will frequently fail of pratical 

 results without experiment and mechanical ingenuity." 

 , . . Mere study of [insects], however, while essential, 

 is not often productive of those important practical 

 results which follow when it is combined with field 

 work and experiment by competent persons and upon 

 scientific principles. Many of tho remedies proposed 

 and recommended in the agricultural Press are either 

 ridiculous or else based on misleading empiricism ; and 

 economic entomology, as a science, is of comparatively 

 recent date. 



Insects probably outnumber in species all other animals 

 combined, some 350,000 having already been described, 

 and fully as many more remaining yet to be character- 

 ised. The proper and consientious characterisation of a 

 genus or species of some microscopic creature involves 

 as much labour as that of one of the higher animals. 

 Of the above number a goodly proportion are injurious 

 to cultivated crops. Lintner recently records no less 

 than 17G affecting the Apple. 



Insecticides. — Of insecticides any number of substances 

 have been recommended, and many of them tried with 

 more or less satisfactiuu, pf tUeso may be mentioned 



lime, sulphur, soot, salt, wood-ashes, corrosive sublimate, 

 naphtha, naphthaline, turpentine, alum, carbolic acid, 

 phenyle, cyanide of potassium, blue vitriol, ammonia, 

 alkalies, benzine, vinegar, sulphuric acid, quassia, vitriol 

 (the suJphate of copper), hot water, &c. Most of these 

 may be safely used for specific purposes, either dry, iu 

 liquid, or in vapour ; but the three most useful insecti- 

 cides of general application in use during the early 

 days of economic entomology iu this country and up 

 to within a few years, were undoubtedly tobacco, white 

 Hellebore, and soap. Tobacco-water and tobacco-smoke have 

 long been employed against aphides and other delicate 

 insects, and are most useful. A quite recent advance 

 in its use is by vapourising. The vapour of nicotine is 

 most effectual in destroying insects wherever it can be 

 confined, as in greenhouses. Thus the boiling of tobacco 

 in such a greenhouse is as effectual as, and less iujurioua 

 to the plants than, the older methods of syringing with 

 a decoction, or of fumigating by burning; whilo ex. 

 perience by Mr. AVilliam Saunders at the Department 

 of Agriculture dm-iug the past two summers shows 

 that the vapoui: gradually arising from tobacco-stems 

 strewn on the ground and regularly moistened is Uke- 

 wise effectual. "White Hellebore, either dry or in liquid, 

 has long been one of tho most satisfactory insecticides 

 against Tenthredinid larv», otherwise known as false- 

 caterpillars, of which the imported Currant-worm (Ne- 

 matus ventricosus) is a familiar type ; whilo soap, 

 syringed in strong suds, will kill some soft-bodied 

 plant-destroyers, and when used as a paint on the 

 trunks of trees is an excellent repellant against the 

 parents of different borers. Transcending in importance, 

 however, any of the.se older insecticides are the three 

 now most commonly used because most satisfactory. 

 They are: — (1) arsenical compounds, (2) petroleum, and 

 (3) Pyrethrum. The first act through the stomach, and 

 are effectual chiefly against mandibular insects ; the 

 second and third act by contact, and are, therefore, of 

 more general application, affecting both mandibular and 

 hausteUate species. — Gardeners' Chronicle- 



Oaloteopis gigantea. — Two out of the three known 

 species of this genus are flowering for the first time 

 at Kew. — Gardeners' Clironicle. 



Pkickly Peak in America. — In some recently publish- 

 ed Consular reports of the United States, the following- 

 interesting paragraph on the Nopal, or Prickly Pear 

 (Opuntia cochiuillifera) occurs : — " The plant abounds 

 iu the whole territory of Mexico, Texas, New Mexico, 

 Arizona, and California, and extends much farther north. It 

 has flat oval leaves, about inches long and nearly 

 half an inch thick, covered by long sharp thorns, and 

 bears a fruit of purple colour resembUug a Pear, filled 

 with numerous small seeds. Tho plant grows from 3 to 

 6 feet high. Its fruit is eaten freely by cattle, and tb-j 

 leaves, after having been burnt in a fire to get rid of 

 the thorns, are thrown by the cartnien in place of fod- 

 der to their oxen by means of a long sharp-pointed stick, 

 especially when on the road where there is no grass. 

 It also makes an excellent hedge, and once planted will 

 last for ever. There is another species of Nopal called 

 Nopal do Oastilla, which has no thorns, and which is 

 cultivated for the sake of its fruit. This Nopal has. 

 much larger leaves than tho wild species, and grows 

 to the height of 10 and 20 feet, and the fruit is muck 

 larger. Of this species there are a great many dift'erent 

 kinds, each having its distinct name. They are of 

 different colours — green, red, yellow, white, and purple. 

 The fruit is delicious, and in the interior of Mexico 

 forms one of tho principal means of sustenance for 

 the inhabitants. Prom the purple Tuna a liquor is made, 

 called Colonche, and a sort of sweet cheese (qiteso de 

 Tuna). There is a small red Tuna growing wiUl in the 

 mountains near to Zacatecas, called Cardona, which is 

 highly prized on account of its fine flavoiu' and degesti- 

 ble qualities, and several cartloads of which arc sold daily 

 in Zacatecas. They are soUl iit G cents for four dozen. 

 Besides serving as food for men and beasts, its leaves 

 form tho food oi thu cochineal m>ice\.,"—Co.rdeiX(,iS' 

 Chrenkk, 



