48 t Jul y> 1888 - 



(which represents a rather young form), shows a remarkable likeness 

 to a young Mytilaspis. I may here remark, that I have found very 

 crowded colonies both of the Mytilaspis pomorum and Aspidiotus 

 ostreceformis heaped together in a confused mass on the same plant, 

 viz., apple, plum, and cherry tree, received from Mr. Douglas, and I 

 notice that Prof. Comstock (op. cit., p. 313) significantly remarks that 

 the genus Chionaspis resembles Diaspis in the form of the scale of the 

 male, and Mytilaspis in that of the female. It must also be remem- 

 bered that the winged males of the different genera are remarkably 

 similar, although they present some difference in the size of their 

 relative parts, as will be seen on reference to Comstock's figures (pi. 

 xxi, Comst,, Eep. U. S. A., 1880). 



The possibility of cross breeding amongst some of the different 

 genera is perhaps suggested by these facts, viz. :— 



(i). Crowded colonies of different genera on the same food-plant, 

 (ii). Great similarity of winged males, which, if not conducive to, 



would not be preventive of cross breeding, 

 (iii). Some of the differential characters of the scales, as shown in the 

 table, appear to be such as might be produced by inheritance 

 from cross breeding. 



The figures given in Plate I are intended to represent some of the 

 typical scales of different genera, and are jfac similes of the drawings, 

 which, as regards shape and size, were made by means of Wright and 

 Newton's microscopic projecting apparatus. It will be understood 

 that the insects living under the scales are not visible in the figures. 



EXPLANATION OF PLATE I. 



Fig. 1. — Uhleria camellice, Comstock. ? , showing first and second exuviae, the latter 

 carinated, skirted by a white scale. 



Fig. 2. — Diaspis ostreceformis, Sign. $ , showing cast skin and scale, the latter 

 slightly carinated. 



Fig. 3. — Aspidiotus zonatus, Frauenf. $ , showing white scale, with a slight ten- 

 dency to carination, and the larval skin slightly cephalically placed. 



Fig. 4. — Mytilaspis pomorum, Bouche. $ , showing first cast skin and large mussel- 

 shaped scale. The second cast skin cannot be.distinctly seen, as in the 

 specimen drawn it was covered with secretion. 



Fig. 5. — Aspidiotus ostreceformis, Curt. $ , not yet adult, showing larval skin, to- 

 wards extremity of the scale, the latter being of an oval form. 



Fig. 6. — Aspidiotus nerii, Bouche. $ , showing the two exuviae and circular scale. 

 N.B. — The above figures are all magnified 1 %° diameters. 



Fig. 7. — Leaf of oleander, attacked by A. nerii (natural size). 



Villa Nova da Gaya, Portugal : 

 June, 1888. 



