6 BULLETIN 265, U. S. DEPARTMENT OF AGRICULTURE. 



occur anywhere on the surface, but are most numerous about the 

 calyx and stem ends, or at a point where the apple touches a leaf or 

 another apple, since it is easier for the larva to obtain a foothold here. 

 Within, the injury is usually more serious, since the larva often 

 burrows to the core and usually hollows out a pupal cell somewhat 

 larger than itself. The burrows vary in length from those just 

 started to holes an inch or two deep. It is quite evident that the 

 larvae are often not entirely satisfied . with the apple as a place of 

 hibernation and that they may begin more than one burrow. Apples 

 frequently have three or four, or sometimes even eight, holes in them 

 of varying depths, but contain only one or two, worms, or often none 

 at all. In making counts of apples in connection with control work 

 a record was kept on this point, and it was found that in 207 damaged 

 apples there were 364 holes, each apple having from one to eight 

 holes, and that of the 364 burrows only 66, or a little over 18 per 

 cent, had been completed and contained worms. 



The burrow is more or less irregular in outline and may be curved 

 or straight. At its end the larva hollows out the slightly larger 

 pupal cell, turns with its head toward the entrance, and forms a plug 

 across the end of the cell, leaving the outer part of the burrow open. 

 This open burrow affords an easy entrance for mold spores, such as 

 those of the blue mold (Penicillium) , and the injured fruit frequently 

 starts to rot shortly after being picked, especially if the weather is 

 moist. The larva seems to be well protected against this mold, 

 however, for the fruit tissue immediately surrounding the pupal 

 cell does not rot very readily, but rather becomes dry and pithy. As 

 long as the larva is not actually drowned in the fermenting juices of 

 the rotting fruit it remains alive and healthy. In March, 1915, a 

 number of healthy larvae were taken from rotten and even mummied 

 Jonathans which had been kept since the preceding September. 

 These larvae were placed on moist sand, and most of them subse- 

 quently pupated and produced adults. 



ECONOMIC IMPORTANCE. 



Since the dock false-worm does not feed upon any part of the 

 apple tree, but must live upon certain succulent plants, mostly of 

 the buckwheat family, it follows that it can become an apple pest 

 only where these plants are growing in or around the orchard. There 

 can be little or no danger from this insect in clean-cultivated orchards, 

 or in orchards where the food plants do not exist. The possibility of 

 the larvae coming into the orchard from neighboring meadows, ditch 

 banks, or roadsides is slight, for the larvae are incapable of finding 

 their way over any extent of bare, cultivated soil. The danger of 

 the larvae adapting themselves to the apple and feeding upon it is 



