206 FOREST ENTOMOLOGY. 



DIASPIKE. 



The sub-family or group Diaspinse may be defined, from a purely 

 entomological point of view, as insects covering themselves by a shield 

 or scale composed partly of discarded skins and partly of secreted 

 matter. Two very common scales viz., the species on ash, &c, 

 and the species on fruit-trees known as mussel scale are very good 

 examples of this sub-family. As there are, however, other forms of 

 scale belonging to this group, it is often somewhat difficult to deter- 

 mine to what genus the scale really belongs. The first point to note 

 is the form of the scale whether it is linear or circular. But this 

 in some cases is not always quite sufficient, as the male scale, or 

 pupartum, must be looked for to determine the genus. Hence the 

 following characters may be given viz. : 



Female scale circular (fig. 196) ; male scale circular (fig. 197) 



Aspidiotus. 



Female scale circular (fig. 198) ; male scale linear (fig. 199) 



Diaspis. 



Female scale linear (fig. 200): male scale linear (fig. 201) 



Chionaspis and Mytilaspis. 



These are most important points to remember, inasmuch as it is 

 sometimes impossible to determine the genera until a male scale is 

 found. 



In fig. 196, which represents a female scale of the genus -4s- 

 pidiotus, a represents the first larval moult, b the second larval 



Fig. 196. Female scale of Aspidiotus. Fig. 197. Male scale of 



a, first larval moult ; b, second larval moult ; Aspidiotus. 



c, portion representing sub-lying body of a, larval moult ; b, secre- 



female ; d, outer secretionary portion of tionary portion, 

 scale. 



moult, c the underlying female, and cl the outer "scale" which is 

 spun by the insect, and thus attached to, but extending beyond, the 



