RADIATION-INDUCED CHANGES IN MELANIZATION AND PHENOLOXIDASE IN CARIBBEAN FRUIT-FLY LARVAE (DIPTERA, TEPHRITIDAE) AS THE BASIS FOR A SIMPLE TEST OF IRRADIATION

First instars of the Caribbean fruit fly, Anastrepha suspensa (Loew), were irradiated with 0, 5, 10, 20, 50, 75, 100, and 150 Gy doses from a Cs-137 source, and observed for whole body melanization as late thir d instars. Control larvae rapidly melanized, whereas larvae irradiated at greater-than-or-equal-to20 Gy failed to show typical melanization after freezing and thawing. Assays of phenoloxidase in control and irr adiated larvae showed greatly decreased enzyme activity at greater-tha n-or-equal-to20 Gy and substantial reduction at lower doses. Larvae we re also irradiated on the 1st d of each instar, and phenoloxidase acti vity was determined when they became late third instars. Larvae irradi ated on the 1st d of the first instar and on 1st d of the second insta r had almost-equal-to90% or greater reduction in phenoloxidase activit y as late third instars. Larvae irradiated on the 1st d of the third i nstar had almost-equal-to50% reduction in phenoloxidase activity at th e time they became late third instars leaving the food to pupate. A si mple spot test for phenoloxidase was developed that produced a red col or with a crushed control larva and no color with a larva irradiated a t greater-than-or-equal-to25 Gy. The radiation induced changes in mela nization and phenoloxidase activity, and a simple spot test may serve as tests for irradiation treatment of Caribbean fruit fly larvae.