Laboratory feeding studies were carried out to determine the effects of the Bacillus thuringiensis (Berliner) CrylAb toxin on developmental time and mortality of Chrysoperla cameo (Stephens) larvae. A bioassay technique was developed that allowed for incorporation of the Cry lAb toxin into a liquid diet that was then encapsulated within small paraffin spheres. Because only 2nd and 3rd instars can penetrate the surface of the paraffin spheres, 2 different methods were used to rear chrysopid

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... e through the 1st instar. The 1st method used small foam cubes soaked in non-encapsulated, liquid diet (with or without Cry lAb). The 2nd method used Ephestia kuehniella (Hiibner) eggs as prey during the first instar (no Cry lAb exposure). After reaching the 2nd ins tar, all larvae received encapsulated, artificial diet with or without Cry lAb, respectively. When reared only on artificial diet containing CrylAb toxin, total immature mortality was significantly higher (57%) than in the respective untreated control (30%). Also, significantly more chrysopid larvae died (29%) that received Cry lAb later during their larval development compared with the respective control (17%). Although mortality was consistently higher, no or only small differences in developmental times were observed between Cry lAb-treated and untreated C. cameo larvae. C. cornea larvae required significantly more time to complete larval development when reared on artificial diet only than when reared first on E. kuehniella eggs followed by encapsulated artifical diet or on only E. kuehniella eggs, regardless of exposure to Cry lAb. These results demonstrate that Cry lAb is toxic to C. cameo at 100 J.tmgl ml of diet by using encapsulated artificial diet.