i05b Mi'.Axs oi' i'K):\i;ntiox and coxtroi. 



The individuals of /). acrivora live as parasites in the cephalic region 

 of Leiu'otcymcs ; they are more nnnieroiis in the neighbonrhood of the 

 month parts. Their nnmber ranges from i to 75 per insect. 



Experiments undertaken in order to ascertain whether the nematodes 

 can be introduced into the body of the Leucotermes and produce the para- 

 sitic affection artificially gave positive results. White ants brought into 

 contact with cultures of nematodes in wet soil were infected and died in 

 12 days. 



827 - The Efficacy of Aphelinus silvestrii in Control of Chrysomphalus 



dictyospermi, in Sicily. — De (iRECORIO a. in Xunn Animli di Agricnltiirii sici- 

 liana, \'lh j'car, Vllh v'icrics, Part I, pp. 18-19. Palermo, January -March 1916. 



In confirmation of his previous observations (i) the writer reports 

 that in the neighbourhood of Palermo he observed so considerable an increase 

 of Aphelinus silvestrii that the latter almost completelv destroyed the fa- 

 mous citrus scale insect Chrysomphalus dictyospermi for which he proposed 

 the new name of Aspidiotus agrnmiiicola. This scale insect has not yet entire- 

 ly disappeared, but the hymenopteron, its natural enemy, has reduced 

 it so such an extent that it no longer causes injury to the plants or their 

 fruits. 



828 - Efficacy of Various Arsenical Preparations in Control of Insect Pests. - ]5.\ttail j 



in Le Progris ap'icole d viticolc, 33rd j'ear, No. 19; pp. 448-452. Montpellier, Maj' 7, 1916. 



The arsenic salts most in use as insecticides are : sodium arsenate, 

 calcium arsenate, lead arsenate, copper arsenite, iron arsenate and copper 

 arsenate. Their toxic action is in proportion to their content of arsenic. 

 We have therefore : 



Calcium arsenate 37.9 "„ of arsenic 



I^ead " 16.7 " " 



Anhydrous sodium arsenate 36.0 " " 



Copper arsenite 34.5 " " 



Iron arsenate 33.6 " " 



Copper " 32.0 " 



This scale of values, however, is slightly modified in practice for sev- 

 eral reasons, the chief of which are : the solubility of the arsenic salt, the 

 formation of salts which act as though they were impurities and lower the 

 percentage of arsenic in the compound, the presence of chlorides, and the 

 addition of Bordeaux mixture for the purpose of controlling mildew at the 

 same time. 



Sodium arsenate is the most soluble, but its action is transitory, and 

 it may seriously burn the green parts of the plants as soon as the dose of 

 I per 1000 is exceeded ; it is therefore only used in the preparationof the 

 other arsenical compounds. 



Calciitm arsenate is the richest in ar.senic and is also the most effec- 



(1) See B. April 1015, N'o. r s i . {Rd). 



