Maskell. — On Coccididas. 5 



entirely as to shades of colour, and what to one may seem a 

 distinct brown may to another appear dark-grey. Writers on 

 Coecids have not, luckily, plunged as deeply as the lepidop- 

 terists into the mysteries of " fuscous-ochreous," "fuscous- 

 blackish," " piceous-fulvous," and so on. We are spared that 

 infliction so far ; and undoubtedly I would not argue that 

 most men cannot tell the difference between "brown" and 

 " white." But, if we begin to consider colour as an important 

 distinction, especially for generic differentiation, I fear the 

 result will beendless confusion. Moreover, as a fact, colour 

 in Coecids is not a constant character. Not only do the 

 insects themselves change with age, but very frequently 

 their shields vary with the food-plant or other conditions. 

 For example, in my species Mytilasjns ijyriformis, iu 

 many cases, the enclosed female, up to gestation, is light 

 " yellowish-brown or greyish " (Scale-Ins. of N.Z., p. 53) ; 

 but after gestation I find it frequently a very dark-browai, 

 almost black. Again, the same insect, on a soft and succulent 

 leaf of Dysoxylou, has a light-brown shield ; on Bhipogonum 

 it is often nearly black ; on the hard bark of a pine-tree it is 

 frequently a very pale yellow. Again, Mytilaspis i^omorum, 

 according to Signoret, has a shield " dai'k-brown ; " Professor 

 Comstock (Ag. Eep., 1880) calls it "ash-grey; " I have seen 

 often some quite white mixed with the brown ones. I believe 

 that hares in Scotland are sometimes brown and sometimes 

 white ; but we could not separate the tw^o generically. 



Professor Comstock's second character — " Scale of male 

 similar in form to that of the female " — is much more reliable ; 

 but it does not go quite far enough, and requires the addi- 

 tional words " not carinated," as I shall point out presently. 



In the Entomologist's Monthly Magazine iox^nly, 1888, Mr. 

 A. Morgan proposes a classification of the Diaspid group 

 based upon what he terms a " tendency " to certain shapes in 

 the puparia. I freely confess that I feel the greatest possible 

 horror of accepting as the basis of anything at all a 

 "tendency;" nor do I sympathize in the least with the 

 prevailing modern fashion of philosophy in this respect. 

 Moreover, in systematic observation it would seem to be 

 extraordinarily difficult, in examining some newly-found insect, 

 to affirm whether it is, or merely " tends to be," something or 

 other : it would be better to take it at once for what it 

 appears to be in fact. But I venture to think also that IMr. 

 Morgan's theory leads him into a want of definiteness and 

 clearness. For example, he separates Aspidiotus from Diaspis 

 as follows: ''Aspidiotus female and male circular, male tends 

 to linear form ; Diaspis female circular, male linear." It would 

 be puzzling to make out a " circular " object " tending to 

 linear form : " why not say " elliptical " at once? Again, his 



