Honeybees cannot synthesize arachidonic acid (ARA) themselves, only obtain it from food. Most pollen is deficient or contains a small amount of ARA. The necessity of supplementary ARA in bees’ diet has not been studied. The objective of this study was to investigate the effects of dietary ARA levels on the growth and immunity of Apis mellifera ligustica. A total of 25 honeybee colonies were randomly assigned to five dietary groups which were fed basic diets supplemented with 0, 2, 4, 6, and 8% of ARA. The diet with 4% ARA improved the body weight of newly emerged worker bees compared with the control group. Supplement of ARA in honeybee diets changed the fatty acid composition of honeybee body. SFA and MUFA contents of bees’ body declined, and PUFA content rised in the ARA group. Compared with the control group, the supplement of ARA in honeybee diets increased the contents of ARA, C22:6n-3 (DHA) and C18:3n-6 in bees’ body significantly, but decreased the contents of C16:1 and C18:3n-3. The diet supplied with 4% ARA reduced the mortality rate of honeybee infected with Escherichia coli. The activity of immune enzymes (phenoloxidase, antitrypsin, and lysozyme) and the mRNA expression levels of immune genes (defensin-2, toll, myd88, and dorsal) were improved by ARA diets to varying degrees depending on the ARA levels, especially 4% ARA. These results suggested that dietary ARA could improve the growth, survival, and immune functions of honeybees. Supplement of ARA in bees’ diet would be valuable for the fitness of honeybees.

蜜蜂自身不能合成花生四烯酸（ARA），只能从食物中获取。大多数花粉缺乏或含有少量ARA。蜜蜂饮食中补充 ARA 的必要性尚未研究。本研究的目的是调查膳食 ARA 水平对意大利蜜蜂生长和免疫的影响。总共 25 个蜂群被随机分配到 5 个饮食组，分别饲喂添加 0、2、4、6 和 8% ARA 的基本饮食。与对照组相比，添加4% ARA 的日粮使新出现的工蜂体重有所改善。蜜蜂日粮中添加ARA改变了蜜蜂体内的脂肪酸组成。 ARA组蜜蜂体内SFA和MUFA含量下降，PUFA含量上升。与对照组相比，蜜蜂日粮中添加ARA显着增加了蜜蜂体内ARA、C22:6n-3（DHA）和C18:3n-6的含量，但降低了C16:1和C18的含量： 3n-3。添加4%ARA的饲料降低了感染大肠杆菌的蜜蜂的死亡率。根据ARA水平的不同，ARA饮食可以不同程度地提高免疫酶（酚氧化酶、抗胰蛋白酶和溶菌酶）的活性以及免疫基因（ defensin-2 、 toll 、 myd88和dorsal ）的mRNA表达水平，尤其是4%阿拉。这些结果表明，膳食 ARA 可以改善蜜蜂的生长、生存和免疫功能。在蜜蜂饮食中补充ARA对于蜜蜂的健康很有价值。