OF WASHINGTON, VOLUME XII, ]<l|(l. 57 







For the present I conclude to regard this as being distinct from the 

 apple bark louse (--Z.. ulini L.). I therefore place it in my collection 

 under the name of Aspidiotus corni. Certainly there is the same ground 

 for deeming the species of this genus, which occur upon plants of dif- 

 ferent genera, to be distinct species, that there is in the genus Lecanium. 



There are instances where a single species has been described 

 under two or three names and each held to be distinct because 

 they were found upon different hosts, although these host- 

 plants might be growing side by side; e. g., notes on "Leca- 

 nium ulmi Fitch MS." ~Lec. corni Bouche contain the fol- 

 lowing: 



May ji, 1854. I met with this speciee on a young elm, beside Black 

 Creek, in Chester Martin's meadow, and near it the closely allied Leca- 

 nium juglandifex and L.corylifex( if these three be not, indeed, one and 

 the same species). 



Under Lecanium corylifex appears the following note: 



May 31, 1854, Found this, plenty, on the under side of hazelnut twigs 

 in Chester Martin's meadow L. juglandifex and L. ulmi Fitch MS. in the 

 same spot. 



Again, Lecanium quercifex and L. quercitron is were de- 

 scribed from specimens on adjacent trees, the former from a 

 white oak and the latter from a black or quercitron oak, found 

 on the same day, June 1, 1854. Fitch records seven varieties 

 of L. quercitronis. 



In this connection it must be understood that all of Fitch's 

 descriptions are based solely upon superficial examination with 

 a hand lens, of the insect in its natural state, mounted on a 

 pin or perhaps on cardboard or mica strips. Every little 

 variation in size, shape, or color was considered important, so 

 that in his notes Fitch frequently has recorded six or eight or 

 even as many as fourteen varieties of a supposed species. 



Remedies. In notes on the more important economic spe- 

 cies, Fitch has recommended various substances and com- 

 pounds for the control of scale insects, which are among the 

 most efficient in use at the present time, e. g., soap; strong 

 lye; potash in water or mixed with lime; whitewash; mix- 

 tures offish oil and soap. Many curious remedies which were 

 proposed by various correspondents for scale-insect control are 

 recorded in the notes, such as solution of aloes in water; 

 refuse brine of mackerel; decoctions of quassia, tansy, worm- 

 wood, or other bitter herbs. 



To Fitch a scale insect upon a new food plant was a new 

 species; and he so described it, almost invariably naming the 



