Trouvelot.] 118 [January 23, 



I am Indebted to Baron Osten Sacken and Mr. Uhler for valuable 

 assistance in determining many of these remains. 



The specimens from the two localities differ so completely as to 

 awaken the suspicion that the rocks of one locality may be older than 

 those of the other. In both places, Mycelophilklce and other Diptera 

 are found, but in Fossil Canon the variety and abundance are propor- 

 tionately greater. The ants, the moth, the thrips, and nearly all the 

 small Coleoptera, are restricted to Fossil Canon, while the larvaj again 

 come from Chagrin Valley. 



Perhaps no general conclusion can be drawn from this small collec- 

 tion, particularly as there is a total absence of means of comparing It 

 with fossil insects of a similar age in this country ; yet while it does 

 not agree In the aggregation of species with any of the Insect beds 

 of Europe, nor with those of the Amber fauna, there can be little 

 doubt that It belongs to the Tertiary Epoch. 



Mr. L. Trouvelot exhibited a specimen of Saturnia ce- 

 cropia, in one primary of which the third costa was only par- 

 tially developed, closing only one half the interspace which 

 it generally spans. He also exhibited a specimen of Bon%- 

 hyx Cynthia^ in which he had artificially caused one primary 

 to expand to only half the extent to which the other wings 

 reached, and in connection with it, presented the following 

 paper: — 



On Monstrosities Observed m Wings of Lepidopterous 

 Insects, and how they may be Produced. 



Very often Lepidopterous insects have been observed with one or 

 more wings considerably smaller than the others ; this imperfect devel- 

 opment of the Avings has been called a monstrosity. So far as my 

 knowledge goes, I am not aware that any one has given an explana- 

 tion of this phenomenon. I have observed how such monstrosities oc- 

 cur, noticed the cause, and have myself partially hindered tlie devel- 

 opment of a wing of an individual of Bomhyx cipitltia. 



Those who have observed Lepidoptera^ know that the wings of 

 these Insects when emerging from the pupa are very minute, and that 

 a fluid issues from the abdomen of the insect to help in the expansion 

 of the wings. This fluid seems to be separately provided on eacii 

 side of the body ; as I have observed in some cases, where one pair 

 of wings had grown faster than the other, that the side of the ab- 

 domen corresponding to the smaller wings was swollen very much 

 more than the other. 



