297 



Clytus pictus, whicli I still preserve, out of a stick of hickory wood in 

 Rock Island, and in the course of the next two or three years I took 

 two specimens in the same neighborhood, which proves that the 

 species has been all the time in existence there, feeding in all proba- 

 bility on our hickories and walnuts. * Is this hickory-feeding insect a 

 distinct species, differing in the larva state, but apparently identical 

 in the imago, or was there a brood of Clytus pictus one hundred years 

 ago in the Eastern States, which acquired a taste for locust wood, and, 

 by the laws of hereditary descent, handed over the taste to their 

 descendants, which have gradually, in the course of a century, spread 

 westward to the Mississippi River ? We are bound, I think, to ac- 

 cept the latter hypothesis until the former one can be proved to be 

 true. Will this locust-feeding race of Clytus pictus, in the course of an 

 indefinitely long period of time ever acquire structural differences in 

 the" larva, similar to those which distinguish the larva of the oak and 

 basswood-feeding Halesidota Antiphola from that of the buttonwood- 

 feeding H. tessellaris ? and is it probable that in the course of a still 

 longer period of time the images may become distinct either in color- 

 ation, or in structure, or in both ? To believe in the present exist- 

 ence of distinct species is one thing — nobody doubts that ; to believe 

 that they have always been distinct, and will always remain distinct? 

 throughout all time from their supposed original creation, is another 

 and a very different thing. 



* After the above was placed in the hands of the Society (Sep. 2), a numerous 

 swarm of the imagos of Clytus pictus has burst forth from the locusts in Rock 

 Island. The locusts in our Court-House Square, which were planted twenty to 

 twenty-two years ago, are now (Sep. M, 1863) full of the borings of this insect, and 

 two or three imagos may be found on the trunk of almost every one of them. 

 Three years ago I carefully examined these same trees, and could not discover a 

 single hole. Yet there are plenty of hickory trees growing within a mile of the 

 Court House. I may add here that Prof. Sheldon, of Davenport, Iowa, has in- 

 formed me that he has repeatedly, for many years back, split Clytus pictus out of 

 hickory wood, and that, so far as he is aware, the locusts in Davenport are not yet 

 attacked by this insect. 



It is well known that the locust-feeding type of this insect occurs in the imago 

 state exclusively mi the autumn. The hickory-feeding type, on the contrary, is said 

 by Mr. Bland to be abundant on that tree in the spring, {Proc. Entom. Soc. Phila., 

 I. p. 95.) Again, Dr. Harris describes the young larvae of the locust-feeding type 

 as " boring in the spring through the sapwood more or less deeply into the trunk, 

 the general course of their winding and irregular passages being in an upward di- 

 rection." {Inj. Ins., p. 104.) Speaking of the hickory-feeding type. Dr. Horn de- 

 scribes the excavations of the larva as beins " immediately subcortical not in a 

 line, but in every direction," and says that it is not till " it is about to become pupa 

 that it bores for a slight deptli into the wood and for a distance of about tliree 

 inches." {Proc. Ent. Soc. Philad., i., p. 30, and compare p. 122.) Hence it would 

 appear that the habits of the two types of this insect differ, especially as to the 

 time of their assuming tlie imago state. Tlie larva of the hickory-teeding type is 

 fully described and figured by Baron Osten Sacken. ( Proc. Knt. Soc. Philad., I. 

 pp. 105 and 121.) I am not aware that there is any full description extant of the 

 larva of the locust-feeding type. 



