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 scemed 

 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 Sepsidae (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. As a 

 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, ii, 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 



