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This was strong evidence that some sort of substance (which we will 

 call a fruit marking pheromone) , secreted from the ovipositor of a 

 female during ovipositor dragging, was preventing; other females 

 from attempting to lay an egg. 



Of what advantage is it to the flies to deposit such a marking 

 pheromone? Examination of hundreds of fruits by myself and other 

 investigators has shown that usually only 1 maggot larva per fruit 

 can survive to maturity if the fruit is small, 5/8 inch or less in 

 diameter. Hawthorne fruit, the original native host of the apple 

 maggot, and sour cherries do not usually exceed this size. There 

 simply isn't enough food or space in such fruits for more than one 

 larva to develop. By depositing fruit marking pheromone following 

 egglaying, a female is in essence saying to other females arriving 

 afterwards, "Don't bother to lay an egg here. If you do, you'll 

 be wasting your energy and your egg. There's only room for 1 larva 

 here, and the larva from my egg already has a head start and would 

 outcompete the larva from any egg you might lay. You're better off 

 if you leave this fruit and look for a different one that isn't 

 marked with pheromone and therefore doesn't already contain an egg." 

 Apples, which the apple maggot began to infest about 110 years ago, 

 are of course much bigger than hawthorne fruit or cherries and can 

 support as many as 15-20 larvae to maturity. Therefore, 15-20 fe- 

 males can lay eggs in and deposit marking pheromone on apples be- 

 fore the pheromone begins to become a deterrent to further egglay- 

 ing. 



During the past 4 years, I (alone, or in conjunction with Drs. 

 Volker Moericke of Bonn, West Germany and Harvey Reissig of Geneva, 

 New York) have continued to explore various properties of this fruit 

 marking pheromone. We have found that if pheromone-marked fruit is 

 kept under dry conditions at normal summer temperatures, the phero- 

 mone is remarkably stable and is nearly as effective in preventing 

 egglaying 2 weeks after its deposition as hours after. Surpris- 

 ingly, the pheromone has proven to be water-soluble, and can be 

 partially washed away by rainfall. This is not necessarily a dis- 

 advantage to us, however. For example, we have been able to swish 

 marked fruit in a container of water, spray the pheromone-water 

 solution onto clean fruit in laboratory cages, and to a substantial 

 degree prevent maggot fly egglaying in this fruit. If combined 

 with an effective spreader-sticking agent, this pheromone should 

 be able to survive considerable rainfall and remain effective under 

 a variety of outdoor weather conditions. 



Recently, we have found this same sort of pheromone to exist 

 in all 6 of the close relatives of the apple maggot that we have 

 examined. These include the blueberry maggot, black cherry fruit 

 fly, eastern cherry fruit fly, and western cherry fruit fly. Drs. 

 Byron Katsoyannos and Ernest Boiler of Wadenswill, Switzerland have 

 also recently found it to occur in the European cherry fruit fly, 

 the worst pest of cherries in Switzerland. This past year, these 

 workers collected marking pheromone deposited after about 1 million 



