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NATURE 



[August 28, igi. 



The work is a striking example of what ran be done 

 when scientific zeal and business capacity have behind 

 them resources such as those of the Carnegie Institu- 

 tion. Dr. Bauer and the staff of the department of 

 terrestrial magnetism — both those who took the ob- 

 servations and those who did the necessary office work 

 — are to be congratulated on the progress made 

 towards the achievement of one of their principal 

 objects of ambition, a general magnetic survey of the 

 globe. C. Chree. 



ADVANCE IN ECONOMIC ENTOMOLOGY. 

 \ NOTABLE feature of recent biological research 

 -**■ is the attention paid by medical experts to the 

 study of insects. Capt. F. W. Cragg, of the Indian 

 Servii e, has lately published two Scientific Memoirs 

 (Nos. 54 and 55) of the Medical and Sanitary Depart- 

 ments of the Government of India, which are of 

 importance to students of the anatomy of Diptera. 

 Both memoirs deal with blood-sucking species, No. 54 

 with Philaematomyia insignis, and No. 55 with 

 Haetnatopota pluvialis. The excessively small number 

 of males of the latter fly is believed by Capt. Cragg, 

 after examination of the genitalia of the female insect, 

 to be explained by heavy mortality as the result of 

 pairing. We notice that the bibliography of this 

 paper contains some remarkable misprints, of which 

 "Verb., yool-bat. Gas. W'ein " is worthy of record as 

 a piece of unconscious humour ! The last published 

 part of the Bulletin of Entomological Research 

 (vol. iii., part 4, December, 1912) contains valuable 

 systematic papers on blood-sucking Diptera, by Mr. 

 E. E. Austen and Prof. R. Newstead, and some very 

 useful diagnoses of the larval stages of African mos- 

 quitoes, by Messrs. F. W. Edwards and A. T. Stanton. 



The same number of the bulletin is noteworthy for 

 a suggestive paper by Dr. J. Dewitz on the bearing 

 of physiology on economic entomology. The author 

 points out, for example, the importance of a precise 

 knowledge of the effect of stimuli due to light of vary- 

 ing intensity and wave-length if luminous traps for 

 destructive moths are to be used to the best advan- 

 tage. Temperature is also found to be a factor in 

 the working of this reaction; "the colder the night 

 the fewer the females (and in particular females 

 with eggs) that are caught by acetylene trap-lamps." 



In a lately issued bulletin (Entomology, No. 113) 

 of the U.S. Department of Agriculture, Messrs. 

 W. D. Hunter, F. C. Pratt, and J. D. Mitchell 

 describe the principal cactus insects of the United 

 States. The "prickly pears" (Opuntia) are well 

 known as furnishing food and habitation for the 

 cochineal insect; since the decline of the cochineal 

 industry, however, these plants were regarded rather 

 as noxious weeds until the recent recognition of the 

 fact that they furnish valuable fodder for cattle. In- 

 sects which injure them are therefore regarded as 

 economically important, and in this short memoir a 

 number of species of various orders are described and 

 figured. 



Some very important observations are contained in 

 a small bulletin (No. :o;,') issued by the Maine Agri- 

 cultural Experiment Station in 1912. Miss Edith M. 

 Patch has apparently shown that the aphid causing 

 "leaf-curl" on the elm (Schizoneura americana) 

 migrates in spring to the apple and other Rosacea;, 

 and becomes the parent of the aerial colonies of the 

 notorious woolly aphid, 5. lanigera. The elm is thus the 

 normal host of the sexual forms in autumn, and the 

 apple is to be regarded as an "intermediate" host. 

 The extreme rarity of sexual forms of S. lanigera on 

 apnle in these countries may perhaps be explained bv 

 a similar unsuspected migration here, though our 



xo. 2287. VOL. gil 



native elm " leaf-curl " aphid (Schizoneura ulmi) is 

 generally regarded as distinct from S. americana. and 

 identical with the polyphagous root-feeding form, S. 

 fodiens. 



The gipsy moth (Porthetria dispar) and the brown- 

 tail moth (Euproctis chryssorhoea) are well-known 

 examples of European insects which, having been 

 introduced into America, have become there Very 

 serious pests. From among the voluminous writings 

 of forest entomologists on these species, one or two 

 recent papers are worthy of especial notice. A. F. 

 Burgess gives an account (U.S. Dept. Agric, Entom. 

 Bull. 119, 1913) of the means by which the gipsy 

 moth extends its range. On account of the excessive 

 weight of the female's body, she is unable to fly, 

 though provided with wings, and the spread of the 

 insect from place to place is carried on mostly during 

 the larval stage. The caterpillars are often artificially 

 though unwittingly transported by farm carts, and it 

 appears that one generally unrecognised evil result 

 of automobile traffic is that these destructive insects 

 are carried far more widely and rapidly than formi rly 

 by the passage of motors along main roads which are 

 bordered by infested woods. The young larvae, how- 

 ever, are provided with a natural means of dispersal 

 in form of long hairs, which enable them to be 

 carried by wind for considerable distances. Some 

 ingenious experiments on this subject have been made 

 bv erecting tall platforms provided with traps in which 

 the little caterpillars are caught on their aerial 

 I journeys. 



As these destructive insects were introduced from 

 Europe, the American entomologists have naturally 

 tried the experiment of importing some of their 

 J natural enemies, and an exhaustive report on this 

 subject has been published bv Dr. L. O. Howard and 

 W. F. Fiske (U.S. Dept. Agric, Entom. Bull. 91, 

 1912). To summarise the mass of material in this 

 j bulletin is impossible, but the magnitude of the work 

 I undertaken may be judged from such a fact as that 

 1 11,000 egg-clusters of the brown-tail moth were im- 

 ported from Europe in the autumn of 1906, and 40,000 

 specimens of a single species of hymenopterous egg- 

 parasite, Pteromalus egregius, reared from these wi re 

 turned out in New England woodlands during the 

 succeeding spring. Many valuable bionomic details 

 with regard to the parasites are recorded, and refer- 

 ence is made to attempts — successful or otherwise — 

 i to introduce predaceous enemies of other harmful in- 

 sei ts into countries where the latter have themselves 

 obtained a foothold. A short special paper on a 

 cognate subject is R. S. Woglum's report on a trip 

 to India and the Orient in search of the natural 

 enemies of the Citrus white-fly (Aleyrodes cilri); 

 this forms Bull. 120 of the Entomological Bureau of 

 the U.S. Dept. Agric. 



A much-needed systematic monograph of the 

 "white-flies," or "snowy-flies" (Aleyrodidse) is com- 

 menced by A. L. Ouaintance and A. C. Baker in the 

 Technical Series, No. 27, of the same bureau. These 

 insects are allied to the Coccida; and Aphidida?, but 

 have received far less attention from entomologists 

 than those two families. In the work now begun 

 their structure, classification, and bionomics are dealt 

 with is fully as possible in the present state of know- 

 ledge; ultimately the authors think that the family 

 mav prove as rich in species as the Coccidae or Aphids. 

 Another valuable systematic paper of economic in- 

 terest is Prof. M. Bezzi's memoir on Indian Try- 

 paneids, or fruit-flies (Memoirs Indian Museum, 

 vol. iii., No. 3, 1913). These are small Diptera in- 

 cluded in what used to be known as the " acalypterate " 

 series of the Museidae. The careful, systematic study 

 of such insects is of importance, and Dr. Annandale, 

 the director of the Indian Museum, is to be con- 



