August 9, 1889.] 



SCIENCE. 



tality from the forming kernels. They were rapidly blighting the 

 grain ; and, unless some friendly hand were raised against them, 

 the wheat-crop would be utterly ruined. Even then, when the lice 

 were countless in numbers, and when the winged forms were 

 rapidly spreading to the oat-fields, the hand of deliverance was 

 easily discerned in the comparatively few but wondrously prolific 

 enemies of the lice, which had already sounded a halt in the march 

 of destruction. A week later, and the enemies of the lice were in 

 the ascendency ; and to-day the lice are nearly exterminated, and 

 the wheat-crop is rescued and the oat-crop saved. Close observa- 

 tion easily demonstrates these truths. Even the careless eye can 

 see the savage insects dining on the lice, or the fatal egg laid which 

 dooms the louse which receives it. 



The fact that farmers are noticing these insects friends, and 

 have now an object-lesson which should be rightly understood and 

 carefully studied, leads Professor A. J. Cook, the Michigan State 

 entomologist, to send out a bulletin on the subject of the enemies 

 of the plant- lice. Some weeks ago he was receiving scores of letters 

 asking about the lice : to-day he is receiving as numerous inqui- 

 ries regarding these friends. That instruction is opportune is evi- 

 dent from such questions as this : " Are these insects going to 

 complete the destruction so actively begun by the lice ? " 



There are two groups of these insect friends, — predaceous and 

 parasitic insects, — both of which are well illustrated on the heads 

 of wheat of iVlichigan fields to-day. Predaceous insects are such 

 as devour their prey, much as the cat or weasel devours the mouse. 

 Parasitic insects are those that lay their eggs on or in their victims. 

 When these eggs hatch, the larval parasite proceeds to feast on its 

 host, which thus serves it for both home and food. In the case 

 before us, as soon as the parasite has devoured the viscera of the 

 louse, it uses the skin or crust as a sort of cocoon. These gray, 

 circular cocoons are now thick among the kernels of every head of 

 wheat, and must have been noticed by every observer who has 

 taken pains to examine. A tiny black fly is by far the most im- 

 portant of these little friends that have come to the farmers' rescue, 

 and saved the wheat, barley, and oat crops. 



The lice that are the victims of these eager parasities are easily 

 distinguished. They are short, rounded, and gray in color. After 

 the larva disembowels the lice, it uses the dry, thick skin as a 

 cocoon, in which it changes to a pupa. Very soon the mature in- 

 sect comes forth from a small round hole in the upper, hinder part 

 of the abdomen, and very soon mates, and commences to lay its 

 many eggs in new victims. Of course, these parasitic larvse fairly 

 swim in the rich nutritious blood of the lice, and so are rapidly de- 

 veloped. Thus we see how it is that the parasites are too much 

 for the lice. Prolific as are the lice, and rapid as they are in de- 

 velopment, yet the parasites are even more so, and thus it is that 

 in ten days the parasites have so outnumbered the lice that the 

 latter have been routed and driven from the field. The little flies 

 are just about one-tenth of an inch in length ; but, tiny as they are, 

 they will save millions of dollars to the farmers of Michigan and 

 adjacent States during this single year. 



The lady-bird beetles are also very active and most efficient aids 

 in the work of ridding the grain-fields of the Aphides. Both as 

 larvje and as mature insects, they feed on the plant-lice, and 

 rapidly deplete their ranks. The beautiful rounded beetles, usually 

 dressed in yellow or orange, and often adorned with black dots and 

 markings, are known and admired by all. Few insects do more 

 good than do these lady-bird beetles. The larvas of these are 

 elongated, dark-colored insects, usually dotted with gray, yellow, 

 or orange, according to the species. So the insect not only does 

 well, but looks well. There are also four rows of black dots which 

 extend longitudinally, which are easily seen without a glass. Other 

 species of lady-beetle larvae are duller in color, and so less con- 

 spicuous, yet equally active and voracious. If any doubt the good 

 work of these insects, especially the larvae, he has but to enclose 

 them in a box with louse-infested wheat-heads, or with plant-lice 

 from any plant. The rapid disappearance of the lice will quickly 

 convince the most sceptical of the valuable service of these pre- 

 daceous friends. These lady-bird beetles are hardly second to the 

 parasite first described, in the work of ridding our grain-fields of 

 the lice. Professor C. JM. Weed believes they take a first place in 

 Ohio in this important service. 



By close watching in the wheat or oat fields, one may observe a 

 large number of very rapid flying two-winged flies. Not only are 

 these very quick, but many are lined with yellow bands, and are 

 very beautiful. These flies, for food, only sip the sweets from 

 flowers, but they lay their eggs on the plants among the lice, and 

 the maggots that hatch from these are perfect tigers.* These syr- 

 phus-maggots seem to be veritable gourmands, as the number ol 

 plant-lice that one will suck bloodless is surprisingly great. These 

 maggots look some like leeches or blood-suckers. The posterior 

 end is large and truncated, while the mouth end is pointed. The 

 color of the young ones is olive green, while the older or more 

 mature maggots are gray, brown, or purple. There are light- 

 brown transverse bands on the back, and one longitudinal one on, 

 each side. These maggots creep along in a slug-like manner, ever 

 reaching into every crevice for the lice. The energetic zigzag mo- 

 tion of the head is very interesting. When it first finds a louse, it 

 stabs him with its sharp mouth-parts, and quickly sucks him blood- 

 less. As the louse shrinks, the maggot swells up. No sooner is 

 one louse victimized than another is seized, and thus these vora- 

 cious maggots will often destroy a half-score of lice in quick succes- 

 sion. Students have often suggested that these maggots must 

 have India-rubber stomachs. From their great numbers and 

 ravenous appetites, we must conclude that these syrphus-maggots 

 are little, if any, behind the Braconid fly and the lady-bird beetles 

 in their good services in helping to save the grain-crops. 



Then the chrysopa-flies, with their beautiful green lace wings- 

 and their brilliant golden eyes, are no mean factor in this warfare 

 against plant-lice. The handsome flies do not feed on the lice,, 

 but the larvae do ; and, as they have insatiable appetites, they do^ 

 excellent execution. These flies lay their minute white eggs oa 

 the ends of short hairs attached to wheat-stems, twigs of fruit- 

 trees, in short, to any plant that is harboring plant-lice. The 

 larvae have strong, sharp jaws, and have well earned the name- 

 " aphis-lion," which has been aptly applied to them. These and 

 the syrphus-fly maggots work in confinement, or while we are 

 holding the aphis-infected plant in our hand. The Braconid fly 

 and the lady-bird beetles, on the other hand, are more timid and 

 quite easily disturbed ; and so, to see them at work, we must ap- 

 proach them with care, and handle them without the least jar. 

 Thus in these beneficial insects Professor Cook describes the little 

 friends that have come to the aid of the farmers, and banished dis- 

 aster. 



BOOK-REVIEWS. 



A Practical Guide to the Climates and Weather of India, Cey- 

 lon and Burmah and the Storms of the Indian Seas. By 

 Henry F. Blanford, F.R.S. London, Macmillan. 8°. 



The leisure following Mr. Blanford's retirement from the me- 

 teorological department of the government of India, which was 

 developed in his charge, has been employed in preparing a general 

 account of the climates and weather of that vast empire ; and stu- 

 dents of meteorology the world over are to be congratulated on 

 having such a work from so competent a hand. 



The book is divided into several parts. Part I. treats of the ele- 

 ments of climate and weather, with particular reference to their 

 Indian features, under such headings as " Temperature," " Baro- 

 metric Pressure and Wind," " Dampness and Dryness," " Clouds. 

 Rain, and Storms." Here we recognize the same simple direct- 

 ness of statement and rational physical explanation of processes 

 that characterize the author's " Indian Meteorologists' Vade- 

 Mecum." The second part treats of the climatic divisions of the 

 peninsula, giving a brief description of the several areas, such as 

 the hills, — under which respectable mountain-ridges of 5.000 to 

 7.000 feet are included, — the plains, the plateaus, and the coasts. 

 This is followed by an account of the weather-maps issued daily 

 from Sinild on the basis of nearly one hundred telegraphic reports, 

 the storms of the Indian seas, and the relation of Indian ramfall to 

 water-supply and drainage. Several appendices contain tabular 

 climatic statistics for 92 stations, lists of storms in the Bay of Ben- 

 gal, and rainfall at 114 stations. 



It is difficult to select inaterial for extracts where all is so peril- 



