30 The Ottawa Naturalist. [May 



Thalictrum zibellinum. Usually a foot high, sometimes 

 larger, slender but firm, with striate siem leafy to the summit, 

 glabrous below the summit; leaves of a dull bluish green above, 

 glaucous beneath, all except the floral glabrous on both faces, 

 the floral with traces of some minute pubescence; terminal leaf- 

 lets about f-inch wide above the middle, the length a trifle less, 

 rather deeplv and not very unequally 3-lobed, the lobes broader 

 than long and verv obtuse, laterals smaller, oval, mostly entire; 

 panicles small, rather compact; sepals of staminate plant round- 

 obovate, very obtuse; filaments gradually clavellate from the 

 base, at summit not approaching the width of the anthers, also 

 not very long; anthers oblong, obtuse; sepals of pistillate plant 

 oval, obtuse or abruptly acute, glabrous, deciduous; immature 

 carpels short pubescent. 



The type specimens of this small member of the white- 

 stamened group are in Herb. Geol. Surv., No. 21,134, and were 

 obtained on Sable Island, off Nova Scotia, July 26 to Aug. 8, 

 1899, by Mr. Macoun. These appear to represent a plant strictly 

 dioecious. 



HOUSE-FLIES AND THE PUBLIC HEALTH.* 



By C. Gordon Hewitt, D.Sc, F.E.S., 

 I^ominion Entomologist, Ottawa. 



In a city like Ottawa and in many other Canadian cities the 

 house-fly problem and the dangers resulting therefrom are of far 

 greater and more vital importance than one is accustomed to 

 find in other cities of less rapid growth and longer establishment. 

 Certain facts, to which reference will be made later, are present 

 which increase the potential danger, already very great, of these 

 ubiquitous pests. Whether you penetrate the huts of the Lapps 

 or swelter in the burning heat of an equatorial clime ycu will not 

 be permitted to forget the existence of the "domestic" house-fly ; 

 there are no means of escape; by street-car, by Pullman or by 

 liner it has a free pass. A fearless, dashing and careless mass of 

 heat-infused vitalit}-. Let the day be cool or dull Musca 

 domestica, as the great name giver Linnaeus described it, is 

 obsessed with inertia, but an hour's sunshine or a warm room 

 and it is as attentive as ever. The activities of most living 

 beings, not excluding man, are dependent on the great source of 

 energy, the sun, but the question of temperature is a matter of 



* An abstract of a lecture delivered before The Ottawa Field- 

 Nat jrali ts' CI lb on Feb. 1st, 1910. 



