162 TEA^S ACTIONS OF THE ILLINOIS 



These confessions of former errors I can freely make, because I am not wedded to 

 any opinion or wish, except that grand axiom, the love of truth. Truth is mighty and- 

 will prevail, and I never hesitate to adopt it, however humiliating it may be to my 

 former eiTors. 



Having found a number of species with some general resemblance, for convenience 

 in study, we group them together and assign to this group a name; this is a genus. 



"When we find in the course of study that the characters of a species are such as to- 

 diflfer from all these groups, we create a new group — genus ; and in the same way out 

 of genera we make families. But we soon weary of the dry details of Comparative 

 Anatomy and the rigidity of SeientLtic Classification. But with the practical we find 

 an unending field of pleasant amusement. As we approach the study of '■^Special 

 Barh Lice'^ we promise only to glance at the unfathomed ocean that lies before us. 

 Here we have devoted much time and made many notes, manj' yet in an unfinished 

 state ; some have been made public and others are in process of publication. On the 

 bark of the " White pine^ ' [Finns strolus) Ave often find a downy substance inhabited by 

 a coccus-like insect. This heretofore has been considered a bark louse, but a little^ 

 patient observation will convince you that it develops into a true four-winged two- 

 clawed plant louse. See my forthcoming report in the Transactions of the American 

 Entomological Society. Another on the leaf of the same plant, supposed to be iden- 

 tical, is a true bark louse. The Lecanium, which we find on many trees — linden, 

 boxelder, ironwood, oak, hickory, prickly ash, etc. — is probably but one species, 

 as I have proven for the first three named trees. I have also observed it on the osage 

 orange. The editors of the American Entomologist, Vol. 1, p. 14, represent another 

 species on the osage orange, a down-producing species, and another quite similar one, 

 which we find abundant on the maple all over the country, has a different specific 

 name assigned, and Dr. Fitch in like manner names one on the grape (Z. fitis); 

 another on the pear {L. ijyri) ; for what good reason we can not conceive. Certainly 

 not because they are on difl:erent trees can this be sustained; for that, as we have just 

 shown, is no reason at all. These are all naked insects, crawling about on the limbs 

 of the trees, not being protected by a distinct scale, as is the apple bark louse; they 

 are greatly troubled by the parasitic chalcis flies , numbers of which I have bred while 

 studying the habits of these bark lice. "We often find on the tree the di-y shell of the 

 Lecanium with a small round hole in its back. This is the work of the parasite as it 

 escapes from its ruined victim. But for this fortunate phase in its natural history, this 

 species would become more. numerous and injurious than the apple bark louse; for I 

 have observed them to produce a much more numerous ofi"spriug. 



The gall-producing insect {Dactylo spharea -citifoUae) on the grape leaf has been con- 

 sidered a bark louse, as well as another of very similar habits on the hickory. These 

 have lately been the subjects of much useful controversy. I have studied them all 

 with the greatest care and desire for truth, and am entirely convinced that they can 

 never be arranged with the bark hce. See my report in the proceedings of the 

 Academy of Natural Sciences, Phila., Jan. 1867, where I show from bred specimens 

 that the grape leaf louse, in the perfect state, has fovu- just as ample wings as any 

 other plant louse, and for a more complete discus.sion I must refer you to a forth- 

 coming report on the hickory leaf gall lice, where I show that many species of hickory 

 gall insects develop their young from eggs in June, and still are plant lice. 



