Abstract: In order to investigate the malformation grade and morphological difference of honeybee worker, Apis mellifera, infected by ectoparasitic mite, Varroa destructor, the honeybee morphologic value by Ruttner (1988) were referred to measure the size of proboscis, wings, hindleg, targit, sternit and then the malformation for foragers, normal younger bees, climbing bees and malformed bees was graded. The results showed that economic performance disappeared for malformed bees whose hind leg length (8.188±0.122) mm, area of wax mirror (2.451 mm²) and cubital index (-0.501) was less than normal young bees, foragers, climbing bees. The area of wax mirror (3.072 mm²), 1/width sternit 6(93.686) of climbing bees was more than others but the body size/leg (56.759) was the smallest. In terms of morphology and structure, the imbalance between the back and the legs may cause the crawling of worker bees. Eight major components for malformed bees were established by high than 85% accumulated contribution rates of correlated matrix. The cluster analysis didn't distinguish the climbing bees with normal bees and discriminated analysis revealed three grades for malformation workers in which A type was close to normal bees, B type was medium and had an incomplete wings, C type had complete absent wings and shortened the leg and abdomen. The wings and abdomen previous variations showed vulnerability and malformation grade that may reflect an adaptive stress tolerance for bee resisted to mite.

Key words: malformation, Vorroa destructor, Apis mellifera, morphologic feature