517 



been found between the forms occurring on the apple and those 

 developing on Hlac. In appearance, those on apple are always of a 

 uniform brown, while those on lilac are pale grey with distinct bands 

 traversing them. The apple form was found to develop from two to 

 four weeks ahead of the lilac form. Attempts to interchange the 

 food-plants of the apple and lilac forms showed that,, while transfers 

 were successful from apple to other trees, in no case could the lilac 

 form of scales be made to live for any length of time on apple or 

 pear, and the scales produced by the apple form on other food-plants 

 were always of the uniform brown colour. 



As several authors have drawn attention to the variation in the 

 number of circumgenital pores of this scale from different food-plants, 

 an extensive count was made, and this showed that the commonest 

 number of these pores for an individual of the apple form is from 

 70-74, while those of the lilac form most commonly have from 

 100-104. A study is now being made of the pygidium of the second 

 instar. 



An examination of the scales and counts of the circumgenital pores 

 show that Coccids of the apple form are found also on the dogwoods, 

 Cornus alba, C. alternifolia and C. nigosa, and on mountain maple 

 {Acer spicatum). The biological development of the insects on C. alba 

 has been studied and is parallel to that of the apple form. The lilac 

 form was found on American ash {Fraxinus americana), European ash 

 {F. excelsior), fringe tree {Chionanihus virginica), laurel-leaved willow 

 {Salix pentandra), large-toothed aspen {Populus grandidentata) , Lom- 

 bardy poplar (P. nigra var. italica), Carolina poplar (P. eugenii), 

 trembling aspen (P. tremuloides), witch-hazel [Hamamelis virginiana), 

 New Jersey tea {Ceanothus americanus) , golden currant {Ribes aureum) 

 and heart-leaved willow {Salix cordata). The biological development 

 of the individuals occurring on the first six named food-plants has been 

 found to agree closely throughout the life-cycle with that of the lilac 

 form. 



It is thought that this evidence clearly indicates that there are two 

 species of the oyster-shell scale. 



Savastaxo (L.). I Controparassiti e gli Insetticidi della Biancarossa 

 degli Agrumi. [Parasitic Enemies and Insecticides in connection 

 with Chyysomphalns dictyospermi.] — Riv. Agric, Parma, xxvii, 

 nos. 29 & 31, 21st July & 4th August 1922, pp. 443-444 & 

 470-471. 



In this brief review the following insect enemies of Chrysomplialus 

 dictyospermi, Morg., are recorded as common in Italiaa citrus planta- 

 tions : Chilocorus bipnstulaUts, L., Exocliomus quadripusMatdis, L., 

 Rhizobius lophantae, Blaisd., Aphelinus chrysomphali, Merc, and Aspi- 

 diotiphagus citrinus, How. These are moderately useful. The value 

 of Prospaltella loiinsburyi, Berl., recently imported from the Azores, 

 remains to be ascertained. Insecticides cannot be dispensed with. 

 Lime-.sulphur has proved advantageous because both lime and sulphur 

 are easily obtainable in Italy, while it can be used by any citrus 

 grower and the firewood required is ready to hand. Fumigation with 

 hydrocyanic acid gas has practical disadvantages. It must be re- 

 membered that C. dictyospermi, which was so threatening a pest on 

 its first invasion of Italian citrus plantations, has gradually become 

 less dangerous, and during the past five years, in spite of the neglect 

 of measures during the war, damage by it has decreased to such a 



