538 FIFTH EEPORT OF THE ENTOMOLOGICAL COMMISSION. 



apple, crab, aud the European mouutain ash {Sorhus aucuparia) in Illi- 

 nois; and I have found it common in apple and pear in New York, 

 Maryland, and southern California, and upon black cherry in western 

 New York. 



Although this insect has been well known for many years, compara- 

 tively little has been written respecting it. This is probably due to the 

 fact that there is another species ( Mytilaspis pomorum Bouche) which, 

 like this, infests the apple, and which is more common and much more 

 destructive. The scurfy bark-louse was first described, but not named, 

 by Harris in his " Insects Injurious to Vegetation" (Flint edition, p. 254). 

 In this description both the scale formed by the male and that formed 

 by the female are well characterized ; but the insects themselves were 

 not studied by Dr. Harris. The description of the scales is remarkable 

 as containing an explanation of their nature and probable mode of for- 

 mation as follows : The minute oval dark colored scales on one of the 

 ends of these white cases are the skins of the lice while they were in the 

 young or larva state, and the white shells are probably formed in the 

 same way as the down which exudes from the bodies of other bark lice, 

 but which in these assume a regular shape, varying according to the sex 

 and becoming membranous after it is formed." This statement must 

 have been overlooked by Dr. Fitch, who many years afterwards, in his 

 first report as State entomologist of New York, p. 739 (35), in writing 

 of the oyster-shell bark louse of the apple, states that " these scales are 

 the relics of the bodies of the gravid females, covering and protecting 

 their eggs." And in his second report, p. 489 (257), Dr. Fitch, in describ- 

 ing the pine-leaf scale {Mytilaspis pinifolice) states that the three parts 

 of the scale represent seemingly the head, thorax, and abdomen of the 

 living insect. 



Through the kindness of Mr. Lintner and the officers of the New 

 York State Agricultural Society I have had the opportunity of studying 

 the Ooccidse in the collection of that society. The specimens were all 

 labeled by Dr. Fitch, and by a very careful study of both the scale and 

 the last segment of the female, of the specimen labeled Aspidiotiis cerasi, 

 I have been unable to find any character which will separate it from the 

 specimens labeled Aspidiotiis furfurus, and all of these specimens belong 

 to the same species as the very common pest of the apple and pear, which 

 has been commonly known as Aspidiotus harrisii. 



The statement made by Sig noret* that this species is the same as that 

 described by Curtis under the name of Aspidiotus [Diaspis) ostreafor- 

 mis is evidently a mistake. M. Signoret has kindly sent me specimens 

 of D. ostreceformis, from which I have prepared the description of that 

 species in this report. 



Scale of female. — The scale of the female is flat, irregular in outline, many bending 

 abrnptly to the right or left immediately posterior to the second larval skin, others 

 straight ; in all the scale suddenly widens near the posterior end of the second larval 



*Annale8 de la Soci^t^ En torn, de France, 1876, p. 604. 



