655 



earlier. In normal seasons, the emergence of the spring brood of 

 adults probably begins about the end of April or beginning of May. 

 In the laboratory, mating and oviposition took place in from 1 to 3 

 days after emergence. The eggs hatched in 8 to 10 days. In northern 

 Virginia, eggs of the second generation hatch about 1st July. Whether 

 all the first-brood larvae transform to moths in the same season is 

 unknown. It seems fairly certain, however, that there is at least a 

 partial second generation, though there is evidently considerable 

 overlapping of the two generations. In the late autumn the larva 

 constructs under the bark scales at the entrance to its feeding galleries, 

 a loose, light, but very tough cocoon of white silk. Observations in 

 1912 and 1913 indicate that many of the larvae hibernate in an 

 immature state, but in the spring of 1913, no evidences of feeding were 

 found among about 100 larvae collected in the field, and all undersized 

 specimens proved to be parasitised. In favourable years immature 

 larvae may succeed in passing the winter successfully in northern 

 Virginia, but the mortality among such larvae due to winter 

 conditions must be very high in this latitude. The larvae usually 

 pupate in the cocoon in which they pass the winter. Of the natural 

 enemies of E. semifuner:dis, two parasites, reared in 1913, proved to 

 be a species of Idechthis and Mesostenus thoracicus, Cress. The former 

 was the commoner and parasitised 13'47 per cent, of a batch of 104 

 overwintering larvae. Itoplectis marginatus, Prov., Mesostenus gracilis. 

 Cress., and Pimpla sp. have also been reared from this species. Among 

 the predaceous enemies, the larva of Tenebroides coiiicalis, Melsh., 

 has been taken feeding upon the borer. Ants and woodpeckers are 

 also important factors in reducing the numbers. The only advisable 

 control measure is the cutting away of the dead bark and painting the 

 wounded areas on the already injured trees which oft'er an opening 

 to this pest. A bibliography of 12 works concludes this paper. 



Robinson (R. H.) & Tartar (H. V.). The Arsenates of Lesid.— Oregon 

 Agric. Coll. Expt. Station, Corvallis, Oregon, Bulletin 128, May 

 1915, 32 pp., 3 figs. [Received 10th August 1915.] 



There are two common lead arsenates, lead hydrogen arsenate and 

 lead orthoarsenate, and these are the main components of ordinary 

 commercial lead arsenate. As there is very little accurate knowledge 

 of the preparation or the chemical and physical properties of the 

 pure compounds, the authors have made a series of investigatioiis on 

 the subject, and details are given of methods used for the preparation 

 of the pure salts. Pure lead hydrogen arsenate, PbHAsO.,,is a %yhite, 

 amorphous, finely divided, fluffy powder containing theoretically 

 33-15 per cent. AsoOa and 64-46 per cent. PbO. Attempts to prepare 

 pure lead orthoarsenate, Pbo(As04),,, which theoretically should 

 contain 25-57 per cent. AsoO-, and 74-43 per cent. PbO, resulted in 

 the production of a new basic lead arsenate, and the authors conclude 

 that lead orthoarsenate is not formed under the ordinary aqueous 

 solutions employed in the manufacture of commercial lead arsenate, 

 and that it is not a component of the commercial materials, as has 

 been formerly supposed. Lead pyroarsenate, from its very constitution, 

 cannot be a constituent of the commercial lead arsenate. The phvsical 

 differences between basic and hydrogen lead arsenate are described. 



