940 



SCIENCE 



[N. S. Vol. XLI. No. 1069 



metric standards, but this could happen slowly. 

 Now that so much is said of scientific man- 

 agement, have the owners of large plants ever 

 taken the trouble to estimate the time spent 

 by their computers on account of our adher- 

 ence to an archaic system? While abroad, I 

 bought me a carpenter's rule in the metric 

 system, and use this in my shop except when I 

 have to use machinery built on the British 

 system. I make fewer mistakes, and have far 

 less difficulty in reading a metric rule than 

 one graduated to sixteenths of an inch. 



The metric system has the advantage in 

 classes in physics that we can spend most of 

 our time on physics, and comparatively little 

 on arithmetic, and perhaps our pupils may help 

 to demand the metric system as the universal 

 standard. Paul F. Gaehr 



PSYLLID.E WINTERING ON CONIFERS ABOUT 

 WASHINGTON, D. C. 



The fact that certain PsyUidse spend the 

 winter upon conifers is well known,^ but little 

 has been put on record concerning this habit 

 in the United States. In the vicinity of 

 Washington five species of Psyllids abundantly 

 winter on Pinus virginiana. I have more than 

 once taken all five on the same day. On a 

 bright day they are very active, hopping quite 

 as vigorously as in summer. The list includes 

 Livia maculipennis Fitch, L. vernalis Fitch, 

 Aphalara calthce Linn., Trioza salicis Mally, 

 and T. tripunciata Fitch. The true food plant 

 or host on which these species breed in no 

 case is pine, the conifer being used only as an 

 alternate food plant and winter shelter. The 

 habit of resorting to conifers is not restricted 

 to the cold season, however, as the records 

 show. Livia vernalis has been taken on pine 

 in June, July and September, also, Aphalara 

 calthce in April, and Trioza iripunctata in 

 April, May and June. 



These Psyllids occur on Pinus tceda also, 

 and to some extent on Juniperus virginiana. 

 Another species of PsyUid — Pachypsylla c- 

 mamma Eiley — occurs from October to Feb- 

 ruary at least upon juniper and hemlock. 



Wintering specimens of two of these species 



1 See especially Eeuter, O. M., ' ' Hemipteren- 

 Pauna der Palaearktischen conif eren, " 1908. 



of Psyllidse differ in appearance from the 

 summer forms. In Aphalara calthce the colors 

 are more pronounced in winter specimens, 

 and in Trioza salicis many individuals taken 

 at this season are notably more pruinose than 

 the summer form. 



Besides psyllids, a variety of other insects 

 resort to pines in winter. They include leaf- 

 hoppers of the genera Empoasca, Erythroneura, 

 Balclutha, and Idiocerus, the cercopid, Clas- 

 toptera, and the Heteroptera, Lygus pratensis 

 Linn., and Piesma cinerea Say. Aradus cin- 

 namomeus Panz. occurs on these trees through- 

 out the year. The assemblage of winter guesta 

 on pine includes also small sawflies, and other 

 hymenoptera, numerous diptera, especially 

 Chironomidse, and a few beetles and spiders. 

 By beating conifers, scaling off bark, search- 

 ing through fallen leaves, and sifting, I have 

 made as numerous and varied a catch on many 

 a winter's day, as I have on some days during 

 the more favored season. I may mention that 

 I sought in vain for Psyllids on pines in Main© 

 in early March, getting only diptera and 

 spiders. 



W. L. MoAtee 



SCIENTIFIC BOOKS 

 Medicine in China. By the China Medical 



Commission of the Eockefeller Foundation. 



New York, 1914. 



This volume, containing 113 pages including 

 the appendices, is a summary of the investiga- 

 tions of Chinese medicine by a commission 

 appointed by the Rockefeller Foundation early 

 in 1914. The commission consisted of Presi- 

 dent Judson, of the University of Chicago; 

 Roger S. Greene, consul-general of the United 

 States at Hankow; Dr. F. W. Peabody, of the 

 Harvard Medical School, and George Baldwin 

 McKibbin. The purpose of the commission 

 was to study the medical schools, hospitals and 

 dispensaries of China with reference to the 

 needs of the country and the desirability of aid- 

 ing these institutions financially or otherwise. 

 The commission has produced a report which 

 is not only informing, but is full of interest 

 and written in non-technical language. 



The statement of the committee that China 



