34 Psyche [April 
plants; I have reared it from mines in leaves of the common milk- 
weed, Asclepias syriaca, and have found apparently the same mag- 
got in leaves of horsemint, Monarda punctata. These two plants 
seem rather unfavorable for the purpose, on account in the one case 
of the abundant milk, and in the other the fiery taste. Yet on 
closer investigation neither of these qualities hinders the miner. 
In the case of milkweed, the miner feeds in the palisade tissue and 
does not touch the laticiferous system lying lower down in the leaf. 
If it should by accident cut into these vessels, it would no doubt be 
drowned in the outflow of milk, but apparently this does not hap- 
pen. It enters and departs by the upper surface. 
In the case of Monarda the explanation is not so easy to get at. 
The hot taste comes from the essential oil, of course, and it seemed 
that this must occur in some tissues not attacked by the maggot; 
but I asked several botanists in vain as to the location of the oil 
deposits. At length Dr. W. N. Steil, of the botanical department 
of the University of Wisconsin, told me that the identical point had 
been investigated in that department; he looked it up and kindly 
wrote me that the oil was found to occur only in the trichomes in 
Monarda. These being entirely superficial organs, of course the 
maggot does not eat them. 
No special instinct would seem to be necessary in either of these 
cases. 
(f) In Melander and Spuler’s paper on Sepside (Bull. 143, 
Wash. Agr. Exp. Station) they mention on page 44 my capture of 
Themira putris L. attending plant-lice on cottonwood, and the 
same record occurs in my Catalogue of Diptera, page 619. Asa 
slight contribution to the history of the spread of the species I will 
add that this occurred four miles north of Brookings, S. D., on Aug. 
9, 1891, ten years before the first record of the occurrence of the 
species in North America, which record was by G. Chagnon, in 
The Entomological Student, 11, 13, 1901; his locality was Montreal. 
My specimens attending plant-lice were on a tree a few feet from a 
privy, and this was probably the source of the flies. I still recall 
my exultation when I succeeded in tracing the species in Schiner’s 
Fauna Austriaca, and found it new to North America. 
(g) Chrysomyza demandata Fabr. was first reported from North 
America by C. W. Johnson in Ent. News, xi, 609, 1900; localities 
were Philadelphia and Riverton, N. J. The year of capture is 
