for all the raisins were standard fold-top 15-ounce cartons with cellophane overwraps. 

 Twenty- four packages of each type of raisins were exposed to large numbers of stored- 

 product insects at the Stored- Product Insects Research Branch Laboratory, Fresno, 

 Calif., beginning April 6, 1967. 



Raisin packages were placed on the floor of a 12- by 12- foot exposure room con- 

 taining large populations of stored- product insects. At least 15,000 insects were 

 added each month, and it was estimated that the room contained between 60, 000 and 

 100,000 insects at all times. A constant temperature of 80 ± 2° F. and relative 

 humidity of 40-45 percent was maintained. 



Because it is extremely difficult to separate related species, the species in the 

 exposure room were divided into the following four groups at time of examination: 



1. Grain beetles: saw- toothed grain beetle, Oryzaephilus surinamensis 

 (Linnaeus); and merchant grain beetle, _0. mercator (Fauvel). 



2. Moth: Indian- meal moth, Plodia interpunctella (Hiibner) . 



3 Flour beetles: confused flour beetle, Tribolium confusum Jacquelin duVal; 

 and red flour beetle, T_. castaneum (Herbst). 



4. Dermestids: Trogoderma variabile Ballion ( =T. parabile Beal); 

 T. glabrum (Herbst); and T_. sternale (Jayne). 



Because the flour beetle and moth groups never exceeded 3 percent of the total, they 

 were grouped together in table 2. 



Six cartons of each type of raisin were examined at monthly intervals for 4 months. 

 Each carton was brushed free of insects in the exposure room and taken to the examina- 

 tion room. There the cellophane overwrap was removed and each carton was brushed 

 again to remove insects between the overwrap and the carton The contents of the 

 carton were poured into a white enamel pan. All insects found inside the carton were 

 counted as they were collected in an aspirator. 



RESULTS / 



Insects infested all of the raisins tested, and the total number of insects in the 18 

 cartons examined increased from month to month (table 1). However, the untreated 

 raisins always had the most insects and the double- oiled raisins had the fewest. For 

 the first 3 months, the nectar raisins had only one-half to one- third as many insects 

 as the untreated raisins, and the double- oiled raisins had about one- tenth as many. 

 After 4 months, the ratio began to level off. In the final examination, the untreated 

 raisins averaged 1,036 insects per carton. The nectar raisins had 586, about three- 

 fifths as many insects per carton as the untreated raisins, and the double- oiled raisins 

 had 383, a little more than one-third as many. 



