254 



the action of the vapour of the chemical. In the last case, the eggs 

 were fumigated for 15 hours. The results of these various experi- 

 ments and the different materials used are given in a series of tables. 

 The results of the dipping and spraying experiments showed in general 

 that eggs treated with compounds having the lowest boiling point, 

 that is, the most volatile compounds permitted most, if not all, of 

 the eggs to hatch, except in the case of compounds extremely active 

 chemically, such as allyl alcohol, which contained ammonia, and 

 chlorpicrin. Spraying resulted in a higher percentage of hatching 

 than dipping. Some compounds, the vapour of which had proved 

 non-toxic to house-flies, were fomid to be toxic to the insect eggs ; 

 such were pinene, terpineol, and geranyl acetate. Others, that are 

 so shghtly volatile that they are ineffective against flies, were found 

 to be toxic to the insect eggs ; these included eugenol, alpha naphthol, 

 ethyl ether, and trimethylene cyanide. As fumigants, these are 

 ineffective. 



Compoimds with low boiling points kill freshly laid eggs more- 

 readily than those in which the embryo is partly or fully developed. 

 Compounds with higher boiling points are more toxic to eggs with 

 fully developed embryos than they are to eggs in which the embryo 

 is only sUghtly formed. Kerosene containing both high and low 

 boiling points is destructive to both young and old, but is only slightly^ 

 toxic to partly developed eggs. 



Fumigation in a saturated atmosphere with ether, ethyl mercaptan,, 

 carbon bisulphide, benzene, carbon tetrachloride and chloroform will 

 kill all the eggs in one hour. 



The toxicity of the vapour of organic compounds to insect eggs is, 

 related to the boiling point and the volatility. As the boiling point 

 increases and the volatility decreases, the toxicity increases. 



Pierce (W. D.). Weevils which affect Irish Potato, Sweet Potato and 

 Yam. — Jl.Agric. Research, Washington, B.C., xii, no. 9, 4th March 

 1918, pp. 601-611, 7 plates. 



The potato, which is a native of the west coast of South America, 

 has a series of characteristic weevil enemies, three of which have been 

 described in a previous paper [see this Review, Ser. A, ii, p. 241]. In 

 this paper a key to the various species is given, and Trypopremnon 

 sanfordi, sp. n., is described from a single specimen from Peru, inter- 

 cepted in quarantine on a potato tuber. 



Weevils that attack sweet potato tubers include Euscepes batatae, 

 Waterh., Cylas formicarius, ¥., C. lurcipennis. Boh., and C. femomlis, 

 Faust. A key to some of the species of the genus Cykis is 

 given. E. batatae is one of the most serious pests of the sweet 

 potato. It has hitherto been recorded from many parts of the West 

 Indian Islands and the known distribution now includes Brazil, 

 Jamaica, Hawaii, Guam, New Zealand and Porto Rico. It probably 

 occurs in many other countries, and strict quarantine should be 

 observed against its introduction. Drawings and descriptions are given 

 differentiating the immature stages from those of Cylas formicarius. 



Palaeop'us dioscoreae, sj). n., a weevil that attacks the tubers of 

 yams, is described from two individuals reared from tubers of Dioscorea 

 batatas from Jamaica. 



