338 



Of the genus Gonocephalum, two species have been studied, viz. : — 

 G. aequale, Er., and G. svnplex, F. With regard to the former, two 

 distinct types of larvae have been bred from adults apparently in- 

 indistinguishable from one another and are described ; whether they 

 represent distinct species is not known. The food of the larvae of 

 G. aequale consists mainly of decaying vegetable matter, but they 

 also eat into certain seeds, notably wheat. The adults do great 

 damage to maize seed in dry land and to newly planted tobacco. 

 They emerge chiefly at the beginning of the rains and lay eggs from 

 March, continuing to do so in increasing numbers throughout the 

 winter. The larvae feed during the winter and pupate just before 

 the next rains. Adults hve a considerable time, individuals having 

 been kept for more than 12 months in confinement. This species 

 abounds chiefly on the diorite, being relatively scarce on the sand 

 veld. Larv^ae of G. simplex are frequently found on the surface of the 

 soil under rubbish, and feed on decaying vegetable matter. The 

 life-history is similar to that of G. aequale. This species occurs on 

 all types of soil. Another species resembhng G. aequale in life-history 

 and habits is Emyon tristis, Fhs., which is commonly associated 

 with it, but is found more abundantly on the sand veld than 

 G. aequale. 



The purpose of the variations in the life-histories of the species 

 studied is difficult to understand. The emergence of the adult at 

 the beginning of summer and the postponement of egg-laying until 

 the first signs of autumn, as in the case of Gonocephalum, Emyon and 

 Zophosis, is most unusual among insects. All these occur on the 

 dioritic loam which forms a very tenacious mud in the wet season, 

 and it may be that this environment does not suit the young larvae 

 as well as dry conditions. Trachynotus spp. live over the wet season 

 in the larval stage, but the larvae have attained considerable growth 

 before the rains begin. The other species, which oviposit at the 

 beginning of the rains, occur mostly on the sand veld. This paper 

 concludes with a key to the larvae of the species discussed. 



Robinson (R. H.). The Calcium Arsenates. — Jl. Agric. Research, 

 Washington, D.C., xiii, no. 5, 29th April 1918, pp. 281-294. 



The author gives the following summary of this paper : — Pure 

 calcium hydrogen arsenate (Ca HAs O4) and tricalcium arsenate 

 [Cas (As 04)2] have been prepared and methods for their preparation 

 outhned. The specific gravity of calcium hydrogen arsenate was 

 found to be 3'48 ; that of tricalcium, 3"31. The solubihty of the 

 former in 100 gm. water at 25° C. was 0-310 gm. and that of the 

 latter was 0"013 gm. A chemical study of the relative stabihty showed 

 that (a) there was no apparent reaction between either calcium 

 hydrogen arsenate or tricalcium arsenate and lime-sulphur when 

 combined at a dilution used in field spraying ; (b) the addition of an 

 excess of calcium oxide to either of the calcium arsenates prevented 

 arsenic "from going into solution ; (c) some commercial substitutes 

 for lime-sulphur reacted with both of the calcium arsenates; 

 (d) the arsenates reacted -with, or became soluble in organic acids and 

 various salts, such as sodium chloride. The composition of various 

 commercial arsenates is given and commented upon. 



