477 



the tree. It is the function of the migrants to seek the winter host 

 and there give birth to the true sexes. Both sexes are wingless, and 

 with the deposition of single eggs by the females the life-cycle is 

 complete. The hibernating nymphs, which remain protected about 

 the crown of the apple during winter and ascend the bark in spring, 

 apparently form a closed cycle of apterous viviparous females 

 persisting on the apple. How long such a colony could maintain itself 

 on apple alone is not known. A parallel is found in Pemphigus tessel- 

 laius, the life-cycle of which includes a spring migration from maple 

 leaf to alder and a return migration to maple in the autumn, as well 

 as a generation of hibernating nymphs remaining at the base of the 

 alder and ascending the stem before feeding in the spring. 



The woolly aphis in Maine would probably be exterminated by 

 natural enemies if it did not change its food-plant, Chalcid parasites, 

 Syrphid larvae and Coccinellid beetles being active enemies. On the 

 elm the Aphid is preyed upon by Syrphid larvae, Capsid bugs and 

 Coccinellids. The study of this Aphid is further complicated by the 

 root colonies that remain underground all the year round, apparently 

 until the roots become too badly damaged for feeding purposes. 



The remedies advocated in this bulletin have been dealt with in 

 the earlier abstract referred to above. 



Separate keys are given based on the life-cycle, structure, and 

 habitat. 



LovETT (A. L.) & Robinson (R. H.). Toxic Values and Killing 

 EflBciency of the Arsenates. — Jl. Agrxc. Research. Washington. B.C., 

 X, no. 4. July 1917, pp. 199-207. 



A preliminary study of the relative toxicity of the arsenates of lead 

 has previously been reviewed [see this Review, Ser. A, iii, p. 759]. The 

 present paper records the continuation and enlargement of that 

 work. Lead h3^drogen arsenate is found to have a higher toxicity at 

 a given dilution than either calcium or basic lead arsenate, and requires 

 a longer period of time to kill nearly mature caterpillars than the 

 smaller ones. The arsenic devoured by insects feeding upon sprayed 

 foliage is not all assimilated, a portion passing through the intestinal 

 tract into the excrement. The percentage of arsenic assimilated 

 depends upon the form of arsenate used ; lead hydrogen arsenate 

 was assimilated readily in these experiments and most of the arsenic 

 was retained in the tissue, while much of the basic lead arsenate was 

 found in the excrement. It requires approximately 0'1595 mgm. of 

 arsenic pentoxide to kill 1,000 small tent caterpillars [^Malacosonui] 

 and approximately 1'84 mgm. of arsenic pentoxide to kill the same 

 number of nearly mature tent caterpillars, irrespective of the particular 

 arsenate used as a spray. Preliminary experiments on the scorching 

 effects of calcium arsenate indicate too severe injury to warrant the 

 practical use of this spray. 



Veitch (R.). The Hornet in Fiji. {Polistes hebraeus, F.).— Colonial 

 Sugar Refining Co., Agric Rept. no. 2, Sydney, April 1917, 16 pp., 

 1 plate. [Received 23rd August 1917.] 



Polistes hebraeus, F., has become one of the commonest insects in 

 Fiji, Its painful sting has given rise to an attitude of unqualified 



