Grain beetles were by far the largest percentage of insects found infesting the 

 raisins (table 2). They amounted to 87 to 97 percent of insects in untreated raisins, 

 70 to 86 percent in the nectars, and 39 to 71 percent in the double-oiled raisins. 

 Although the double-oiled raisins had many grain beetles, the nectars had more, and 

 the untreated raisins had the most, at every examination. 



Dermestids were numerous in all types of raisins at every examination and were 

 not adversely affected by the oil treatments. After the first and third months, the 

 nectar raisins actually contained more dermestids than the untreated raisins, and at 

 the second and fourth examinations, they contained only slightly fewer. The number 

 of dermestids in the double- oiled raisins was considerably less than in the untreated 

 raisins for the first 2 months, but at the third month it was only a little less. At the 

 fourth month, the double-oiled raisins had more than twice as many dermestids as the 

 untreated raisins. In this examination, dermestids even outnumbered the grain 

 beetles. 



Flour beetles were found in all types of raisins at all examinations, but very few 

 were found compared with the numbers of grain beetles and dermestids. A few moth 

 larvae were also found in the untreated raisins each month and in the nectars at the 

 third and fourth months' examination. Flour beetles and moth larvae comprised not 

 more than 3 percent of the total insect count in each examination. 



DISCUSSION 



Although the oil treatments did not prevent insect infestation of the raisins, they 

 did reduce the number of certain kinds of insects. Grain beetles were the most abun- 

 dant insects in the raisins in every instance except in the double- oiled raisins at the 

 fourth month, when they were outnumbered by dermestids. 



Although the oil treatment does make raisins less attractive to certain insects, 

 raisin processors probably would not want to increase the amount of oil added to nectar 

 raisins, because additional oil increases the cost and causes raisins to have an oily 

 appearance. 



The double- oiled raisins stained the cartons by the time the test was completed. 

 This staining could be avoided by using a new type of carton with a polyethylene coating 

 on its inside surface. 



The test work showed the need for packaging that will protect both oiled and natural 

 raisins from insect infestation. Further studies of the preference of insects for natural 

 or nectar raisins might also be of interest. 



