Cut cantaloupes in half. Remove and discard seeds and any soft melon at surface of center cavity. With melon-ball cutter, scoop out as many cantaloupe balls as possible (or peel cantaloupe and cut into 1-inch pieces). In large heat resistant, non-aluminum bowl, combine cantaloupe and onions.

In a 3-quart saucepan, combine sugar, vinegar, allspice, cloves, and salt. Heat to boiling over high heat; pour over cantaloupe and onions. Place a salad plate or saucer directly on cantaloupe and onions to keep them below the syrup. Set aside at room temperature until cool - about 1 hour. Cover and refrigerate overnight.

The next day, transfer cantaloupe, onions, and syrup to heavy, 5-quart, non-aluminum saucepot; heat to boiling over high heat, stirring frequently. Reduce heat to medium and simmer, stirring occasionally, 20 minutes.

For short term storage, heat three 1-pint jars with clamp type lids in canner with enough water to cover to boiling; remove from water and drain well. With a slotted spoon, pack pearl onions and cantaloupe into hot sterilized jars, leaving 1/4-inch space at top of jars. Ladle hot pickling liquid into jars to cover onions and cantaloupe; wipe jar rims clean. Close jars tightly; cool to room temperature on wire rack, then store in refrigerator and use within 2 weeks.

For longer storage at room temperature, sterilize three 1-pint canning jars and their lids and bands for processing following manufacturer's directions; drain well. Pack onions and cantaloupe into hot sterilized jars and ladle hot pickling liquid into jars to cover pickles as directed above. Wipe jar rims clean. Seal jars; process in boiling water bath 10 minutes. Cool jars on wire rack to room temperature. Label jars; store in cool, dry place. Use within 1 year. Once opened, store in refrigerator and use within 1 week.