SCIENCE 



pungent Eucalyptus and the highly tannic acacias, the black locust, 

 and all kinds of fruit-trees and shrubs, including the Citrus tribe : 

 when hard-pushed, it will even be content with grass and weeds 

 for a while. Being enormously prolific, and thus far apparently 

 free from any effective enemy but man, its spread is very rapid, and 

 its attack most formidable and quickly fatal, even to large trees. 

 It is very tenacious of life in all its stages of development. Its eggs, 

 stowed away in thick masses of white wool, are very difficult to kill, 

 as most insecticide-washes will rebound harmlessly by capillary 

 repulsion. 



The most fatal work of the Icerya has been done in the orange- 

 groves of Southern California, where even the most persistent fight 

 against it, with every variety of insecticide-washes, has only par- 

 tially checked its ravages, and has nowhere succeeded in extirpating 

 it entirely from an orchard, in consequence of the difficulty of reach- 

 ing effectively both surfaces of every leaf in the dense-topped ever- 

 green-trees. Even when the foliage, and therefore at least one 

 crop of fruit, has been sacrificed by the use of caustic alkaline 

 washes, success has not been complete. 



The use of gaseous insecticides within a gas-tight tent lowered 

 over the trees, has long been suggested against this, as well as 

 other insects infesting evergreen-trees ; but experiments made, e.g., 

 with vaporized carbon bisulphide, have not given satisfactory re- 

 sults in practice. Either the insects were not completely destroyed, 

 or the foliage was seriously harmed when the treatment was long 

 continued. 



The repression of the Icerya having at last become a life-and- 

 death question for some of the older citrus-orchards, it was deter- 

 mined by some orchardists in the neighborhood of San Gabriel to 

 have the feasibility of gaseous insecticides thoroughly tested. At 

 their request, Mr. F. W. Morse, assistant in charge of the agricul- 

 tural laboratoiy at the University of California, was detailed for 

 this purpose ; and the experiments made by him during nearly two 

 months have furnished some scientifically interesting results, while 

 demonstrating that cyanhydric gas can be made fully effective with- 

 out harm to the foliage, and that seven other gases tried were either 

 too slow in their action on the insect, or caused severe injury to the 

 foliage. These other gases were chlorine, sulphuretted hydrogen, 

 ammonia, carbon monoxide, o.xalic and formic acids, and carbohc 

 acid. A summary statement of these experiments is given in Bulle- 

 tin No. 71 of the California E.xperiment-Station, just published. 



Several interesting facts are thus brought out. One is, that ap- 

 parently no practically adequate insecticide effects are produced 

 when these effects depend upon the respiration of the gas by the 

 insect ; the respiratory action being so very slow, as compared with 

 that of the higher animals, that anesthetic rather than toxic effects 

 are produced within the practically admissible limits of time : 

 while within these limits the foliage also suffers, as a rule. 



Cyanhydric gas, acting directly upon the nervous system through 

 the nerve-ends, is quickly fatal, independently of respiration, and 

 even in very small amounts. It is slow in affecting the insects' 

 eggs inside of their woolly casings ; but an effective insecticide dose 

 also acts very injuriously on the leaves of the trees. 



To prevent the latter effect, intermixture with some other gas be- 

 side air suggested itself. Experiments with sulphuretted hydrogen 

 gave unfavorable results. This gas seemed to mitigate only the 

 action on the insects (by anaesthesia). Complete success was, how- 

 ever, attained by the use of carbonic gas, evolved from sodic bicar- 

 bonate at the same time that the cyanhydric gas was evolved from 

 potassic cyanide. The insects were killed as promptly as when air 

 alone was present, but even a lengthy application did not affect the 

 foliage in the least. The minimum proportion of the bicarbonate 

 required for full protection was, for the case of a tree having a top 

 twelve feet in diameter covered by an air-tight tent, a pound and a 

 half, ten ounces of the cj-anide being used at the same time. 



It is not easy to conceive the exact cause of the protective action 

 of the carbonic-dioxide gas upon the leaves ; but there can be no 

 question as to the fact, and it is hoped that further investigation will 

 throw light upon the problem. The board of supervisors of Los 

 Angeles County ha-.'ing requested a further elaboration of the de- 

 tails of the process by Mr. Morse, the latter will have full oppor- 

 tunity for testing the conditions and limits of the action of both 

 gases, and upon deciduous as well as citrus trees. The high value 



i 



[Vol. X. No. 230 



of the latter renders the process perfectly available for them, even 

 if, on accountjOf the later hatching of unscathed eggs, the operation 

 should have to be repeated. Whether the same will hold good of 

 other orchard-trees, and whether their leaves will experience the 

 same adequate protection from the presence of carbonic gas, remain 

 to be seen. E. W. Hilgard. 



University of California, June 13. 



University of New Zealand. 



I HAVE just received your issue for June 3, with the ' New Zealand 

 Letter ' therein, dated Dunedin, April 20. As the agent in London 

 of the University of New Zealand, permit me to supplement the 

 exceedingly inadequate account of that body given by your cor- 

 respondent. He states correctly that the university, like its proto- 

 type in London, does not teach ; but he only hints at powers to 

 confer degrees, and says not a word about any examinations. As 

 a matter of fact, so anxious is its senate to make its degrees worth 

 having, that the whole of its degree-examinations are conducted by 

 English examiners, who are instructed that their standard of ex- 

 amination is to be at least as high as that of the University of 

 London, for corresponding degrees. At the present moment I am 

 seeing through the press no fewer than eighty-six degree-examina- 

 tion papers, set by fourteen examiners, all men of the highest 

 standing, and present or past examiners in either Oxford, Cam- 

 bridge, or London Universities. These papers will be worked in 

 New Zealand in November, and the answers transmitted to me. 

 After their revision by the examiners, a meeting of these gen- 

 tlemen will be held in London, and the results will be trans- 

 mitted to Wellington by cable. This has been going regularly 

 on for more than seven years, and there are now nearly one hun- 

 dred candidates for degrees every year of both sexes. This, from 

 a total population of not exceeding half a million, speaks well for 

 the colony. The degrees conferred as yet are in arts, laws, and 

 science, but provision is made for degrees in medicine and in 

 music. 



The examinations are, I believe, held in different towns in the 

 colony simultaneously. The ' peripatetic annual session ' of which 

 your correspondent speaks, is simply the annual meeting of the 

 university senate. Its members are scattered over a very large 

 area (travelling-facilities are not great), and hence the senate 

 usually does all its work for the year at one sitting, which lasts for 

 several days. Wm. Lant Carpenter. 



London, June 13. 



The Maxillo-Palatines of Tachycineta. 



If Dr. Shufeldt will consult my note in Science for May 13, he 

 will find that neither the accuracy of his figure, nor the entirety of 

 the specimen from which it was drawn, is there called in question. 

 It is evident, to one acquainted with the palatal region as it is found 

 in the swallows, that Dr. Shufeldt's figure represents a skull with 

 mutilated or abnormal maxillo-palatines, in either case not perfect. 



mxp 



Since Dr. Shufeldt says his specimen is not broken, it must be ab- 

 normal. The extent and importance of the alterations Dr. Shufeldt 

 charges me with having made in hastily tracing this figure, can best 

 be understood by comparing the tracing (Fig. i) with a reproduc- 

 tion of the original (Fig. 2). Fig. 3 shows the maxillo-palatines 

 approximately correct. Frederic A. Lucas. 



Washington, D.C., June 15. 



