THE PINE-BARK CHERMES; ITS HISTORY. 183 



are white, transparent, and folded roof-like over the body.* The sex 

 of this form, or whether both sexes are embraced under it, seems not 

 yet to have been determined. They have not been observed in copu- 

 lation or in the deposit of eggs. There is abundant room for careful 

 study in the life-history of this species, such as has been given to closely 

 allied forms, in the admirable paper of Messrs. Riley and Monell, giv- 

 ing biological notes on the Pemphiginae.f 



The above natural history of the species is mainly from observations 

 made upon it during the years 1878 and 1879, by Prof. Herbert Osborn, 

 of the Iowa State Agricultural College, to whom also we are indebted 

 for the figure used in illustration. 



History. 



An unfortunate mistake was made by Dr. Fitch in describing this 

 insect, in his First and Fourth Reports [loc. cit.), as two distinct species. 

 The single-jointed tarsus, the simple organization, and the waxy cov- 

 ering, led him to regard it as a Coecufi, his first published observations 

 upon it not having been continued long enough to show him its sub- 

 sequent development into the winged stage. When in after years 

 the winged individuals were met with, their Aphidian character was 

 at once recognized and they were correctly referred to the genus 

 Chermes, but without associating them with the wingless forms pre- 

 viously observed. And again in this stage, his usual careful habit of 

 observation is not apparent, for although the life-history of " the first 

 true Chermes that has been observed in this country," should have 

 entitled it to careful study at his hands, the following statement is quite 

 at variance with the later observations of others: 



The females [winged] do not extrude their eggs, but clinging closely 

 to the leaf with their heads toward its base, they die, their distended 

 abdomens appearing like a little bag filled with eggs. The outer skin 

 of the abdomen soon perishes and disappears, leaving the mass of eggs 

 adhering to the side of the leaf, but completely covered over and pro- 

 tected by the closed wings of the dead fly.J 



* Prof. Osborn, who has apparently made a careful study of the venation of this insect, 

 states that "the posterior wings have a subcostal vein with no branch veins." A different 

 statement was made by Dr. Fitch in that the longitudinal rib-vein of the hind wings 

 " sends off, forward of its middle, a branch almost transversely inward, its tip curved 

 backward." Dr. Shimer corroborates Dr. Fitch, in stating from his examination of living 

 specimens that " the posterior wing has only a rib vein which forks opposite the quite con- 

 spicuous hook." 



\ Bulletin of the U. S. Geological and Geographical Survey of the Territories, v, 1879, 

 pp. 1-17. 



\ See above, from the observations of Prof. Osborn, the occurrence of w't«^Z«ss females 

 with their extruded eggs [and pyriform body during egg-laying], within little downy balls 

 fastened to the bark. Of Chermes laricis, of Europe, it is stated that as the apterous female 

 slowly deposits her eggs, she partly covers them with the down that she strips from her 

 body, and that they are piled around and upon her until she is nearly half buried in the 

 mass. 



