INJURIOUS AND BENEFICIAL INSECTS OP CALIFORNIA. 307 



Food.— Nearly all forms of stored grains, including barley, chick 

 pea, corn, kaffir corn, oat and wheat, are attacked. 



Control.— The successful control of this weevil depends upon care- 

 fully carrying out certain details, among which are the following : 



1. Prompt cutting and threshing of the grain as soon as ripe to prevent infesta- 

 tion in the fields and subsequent introduction of the weevil to the granary. 



2. The use of only dry, well ventilated, tight bins and granary. 



3. Clean methods in handling the grain both in field and granary, 



4. The treatment by fumigation of infested material before storage. 



5. Frequent inspection of the granary and prompt treatment as soon as pest 

 appears. 



TREATMENT 



There are three important methods used in the treatment of stored 

 grain and manufactured grain products for mill insects. They arc. 

 (1) fumigation with carbon bisulfid, which is specially good for grain 

 or products stored in tight, shallow bins; (2) fumigation with hydro- 

 cyanic acid gas in cases where the bins are large and deep, and (3) 

 the heating method which is specially recommended for large mills. 

 Of the three carbon bisulfid is most dangerous, because of its inflam- 

 mable and explosive character, and it is quite expensive. Hydrocyanic 

 acid gas is dangerous to humans and quite expensive. Either of these 

 processes, however, if carefully executed is quite practical for treat- 

 ment on a small scale. The heating process is very expensive to install. 

 but after the installation it is the cheapest, safest and most successful 

 way to handle any insects infesting stored cereals or products made 

 from them. 



(1) Carbon Bisulfid. — Before fumigating, care should be taken to 

 make the container as tight as possible. The temperature should 

 be seventy degrees Fahrenheit or above, as poor and unsatisfactory 

 results are sure to follow even excessive doses at a lower temperature. 

 In a tight compartment 5 pounds of carbon bisulfid to every 1,000 

 cubic feet of air space gives excellent results in killing the weevils. 

 If the compartment can not be made tight the amount of carbon 

 bisulfid should be increased. 



(2) Hydrocyanic Acid Gas.- — -This is specially recomemnded for 

 large, deep bins or roomy storehouses and should be used at the rate 

 of from 1 to 4 ounces of potassium or sodium cyanide to 100 cubic feet 

 of air space, the amount depending upon the relative tightness of the 

 room. 



(3) Heating. — A steam heating system is necessary to carry out this 

 process and must be sufficient to maintain for several hours, in all 

 parts of the room or mill, a temperature of from 118 to 125 degrees 

 Fahrenheit. 



THE RICE WEEVIL 221 

 Calandra oryzm Linnaeus (Family Calandridse) 



Description.— The weevils are very dark-brown or nearly black. 

 with two reddish spots at the base and two spots of the same color 

 near the tips of the wing covers. The dorsum of tin 1 prothorax is 

 densely pitted with minute round holes. The adults are about ,'-, inch 



-'This species may be distinguished from the granary weevil by the darker color 

 and the spots on the elytra, the round instead >>( oblong punctures on the dorsum of 

 tlie prothorax and by the presence of wings. 



