77 



cent, of cyanogen, and commercial sulphuric acid. The cyanide was 

 used in solution by dissolving 4 lb. sodium cyanide in 1 U.S. gal. water. 

 The formula used was : — Sodium cyanide in solution 2-|oz., sulphuric 

 acid 1 oz., water 1 oz. 



Taken collectively the results show that the killing of 100 per cent, 

 cannot be depended on where the larvae are in balls of earth round 

 the roots of plants, if a dosage is used that will not injure the 

 stock, especially in the case of moist and soaked soil. Since the 

 effectiveness of hydrocyanic-acid gas under vacuum conditions i.~ 

 influenced by the water content of the soil, the death of 100 per cent, 

 in soaked soil could not be obtained with dosages ranging from | oz, 

 to 3 oz. per 100 cubic feet of space. By far the best results were 

 obtained where a prehminary 15-inch vacuum was followed by an 

 exposure of one or more hours under normal atmospheric conditions, 

 100 per cent, of the larvae oi Allorrhina ratida, Agriotes manciis, Popillia 

 japonica and Lachnosterna sp. being killed by this treatment. Of 

 the various larvae used Popillia japonica was the most difficult to 

 kill and A. nitida was the most susceptible. 



With our present knowledge of Vacuum fumigation with hydrocyanic- 

 acid gas, a dosage exceeding 1 oz. of sodium cyanide per 100 cubic feet 

 of space with an exposure of 1| hours is not recommended for plants 

 in fohage. Inasmuch as all larvae in soaked soil are not killed with 

 dosages varying from |- oz. to 3 oz. per 100 cubic feet of space, it follows 

 that fumigation at the port of entry with a dosage that will not injure 

 the plants cannot prevent the introduction and estabhshment of all 

 subterranean pests. 



OsBORN (H,). The Meadow Plant Bug, Miris dolahratus. — Jl. Agric. 

 Research, Washington, D.C., xv, no. 3, 21st October 1918, 

 pp. 175-200, 5 figs., 1 plate. [Received 11th December 1918.] 



Miris dolahrains, L. (meadow plant-bug), has been a conspicuous 

 insect in timothy grass meadows in portions of the eastern United 

 States during the past 40 years and now has a distribution as far 

 west as IlUnois and Mimiesota and south in the Mississippi Valley 

 into Kentucky, It is beheved to be an introduced species, coming 

 from England with timothy hay or other large-stemmed grass shipped 

 for forage or packing some time between 1800 and 1825. It feeds 

 upon cultivated grasses, especially timothy, orchard grass and meadow 

 fescue, and when abundant must seriously affect the value of the crop. 

 It is a dimorphic species, there being two forms of females, a long- 

 winged and a short-winged form, the latter being far more plentiful. 



It hibernates in the egg-stage ; hatching occurs about 25th May to 

 loth June in Maine ; the nymphs pass through five instars of about 6 

 or 7 days each, adults occm-ring from early July, mating and laying 

 eggs from 10th July to 1st August. In the case of the short-winged 

 forms this necessarily takes place in the fields where the females have 

 developed. The eggs are laid in stems of grass or clover, being thrust 

 through the wall of the stem and held by an expanded cap which is 

 firmly contained by the walls of the stem ; they are thus protected in the 

 hollow of the stem and remain in this position for at least 8 or 9 months 

 before hatching. Remedial measures should consist especially of 

 rotation, with probably some advantage from burning, early cutting, 



