BIOSYNTHESIS OF WAX IN THE HONEYBEE,

-The composition of the cuticular wax of the honeybee is quantitatively different from that of the comb wax. The major component of the cuticular lipids is hydrocarbon, which comprises 58% of this wax. In contrast, hydrocarbon comprises only 13-17~ of the comb wax, and monoester is the largest component (TULLOCH 1971). The major fractions of the cuticular wax were analyzed by gas--liquid chromatography, and were shown to be qualitatively similar to those of the comb wax. The incorporation of injected radio-labelled acetate into hexane extractable wax by worker honeybees not actively producing comb wax resulted in the recovery of much of the radioactivity in the hydrocarbon fraction. In insects actively producing comb wax, a higher percentage of radioactivity was recovered in the monoester fraction. A dramatic effect of age on the distribution of radioactivity from acetate into the various wax fractions from honeybees studied in the summer months was observed. In insects from eleven to eighteen days following emergence to adults, the major wax component synthesized was monoester, whereas in younger and older insects, hydrocarbon was the major wax component formed. Both in vivo and in vitro experiments using insects actively producing comb wax showed that the abdomen produced significant amounts of monoester, hydrocarbon, and other esters, whereas the thorax synthesized mostly hydrocarbon. These data show that the epidermal cells and wax glands each produce a wax with a distinct composition, and that the age and seasonal differences observed in wax synthesis are due to the presence or absence of active wax glands. Key Word Index: honeybee, Apis mellifera, beeswax, hydrocarbons, wax esters. I N T R O D U C T I O N BEESWAX consists of complex mixtures of hydrocarbons, esters, and other aliphatic compounds. It is one of the oldest commerical products in man's history, and its chemistry has been extensively studied (TULLOCH 1970, 1971; TULLOCH and HOFFMAN 1972; HOLLOWAY 1969). However, despite a great deal of interest in the chemistry of beeswax, there have been few studies on its biosynthesis. In vivo work by YOUNG (1963) and PIEr (1964) showed that radio-labelled acetate was incorporated into beeswax, and recently BLOMQUIST and Rms (1979) and LAMBREMONT and WYKLE (1979) have described a microsomal system which synthesizes the cuticular and comb wax esters. Considering the different functions of the comb wax and the cuticular wax in the honeybee, and the fact that comb wax is produced by abdominal glands while the cuticular wax is most probably produced by epidermal cells, it was thought that the cuticular wax might have a different chemical composit ion from that of the comb wax. To explore this possibility, the cuticular wax of the honeybee was analyzed and the results presented in this paper show that its composit ion is quantitatively different from that of comb wax. The development of wax glands in the honeybee has been shown to be an age-related phenomenon (GARy 1975). Since considerable differences were observed between the composit ion of the cuticular and comb waxes o f the honeybee, the effect of age on the incorporation of labelled acetate into the various wax fractions was compared. These data, along with studies demonstrating differences in wax production between wax gland enriched and epidermal cell enriched preparations suggest that the age-related and seasonal differences in the composit ion and production of wax by the honeybee are due to the presence or absence of active wax glands. M A T E R I A L S AND M E T H O D S