ORTHOPTERA OF NOVA SCOTIA. — PIERS. 249 



destroyetl. As it is also poisonous to higher animals, the 

 building should be vacated during the fumigation, and after- 

 wards verj'^ thoroughly aired before re-occupation. It 

 must be borne in mind that bisulphide of carbon is violently 

 explosive in presence of j&re, and the very greatest precaution 

 should be taken that no fires or lights whatever are about 

 the premises until after they are thoroughly freed of every 

 trace of gas. The fumigation had better be done, in any 

 case, only b}'^ experienced persons. When possible, super- 

 heating is a comparatively simple and very effective means 

 of destroying cockroaches a? well as other household insects. 

 Cockroaches cannot withstand a temperature of 120° F. 

 for more than a few minutes, and the maintenance of a tem- 

 perature of from 150° to 160^ F. for several hours should 

 result in killing every insect in a building. Sodium fluoride, 

 pure or mixed with equal parts of plaster-of-paris, strewn 

 about the haunts, is a simple and very effective means of 

 control. Temporary relief from the roaches may be gained 

 by the liberal use of fresh pyrethrum powder (Persian insect 

 powder), which is quite safe. The dead and paralyzed roaches 

 may afterwards be swept up. Flowers-of-sulphur is also a 

 good repellant. (For other information on this subject, see 

 L. O. Howard's circular No. 46, 2nd series, U. S. Dept. of 

 Entomology, Wash.; also E. P. Felt's "Household and Camp 

 Insects", bulletin Xo. 194, X. Y. State Museum, Albany, 

 1917.) 



Subfamily Blattinae (Cockroaches, in part). 

 (PeriplanetincB of former writers.) 

 Wing-covers and wings variable in different species; 

 last ventral segment of female compressed so as to form a 

 ridge on its under side, and divided so as to be bivalved; 

 fore femora armed beneath on inner margin with many 

 spines; subgenital styles of equal length. — This subfamily 

 contains our larger cockroach, an introduced species like 

 the one last mentioned. 



Proc. & Tkass. X. S. Inst. Sci., Vol., XIV " Trkns. 17 



