In nature, competing species often achieve coexistence through niche differentiation. We examined this phenomenon for Pachycrepoideus vindemmiae and Spalangia endius (Hymenoptera: Pteromalidae), two species of pupal parasitoids that are considered biological control agents of house fly, Musca domestica (Diptera: Muscidae). We examined the ability of each species, alone and in combination, to locate host pupae buried at different depths (0, 1, 2, 4, and 6 cm) in three types of substrate (sand, dry wheat bran, and spent fly diet). We then evaluated the competitiveness of each species by allowing first one species, then the other species, to parasitise host individuals within time periods ranging from less than 2 hours to 96 hours of each other. Spalangia endius exhibited greater ability than did P. vindemmiae to locate host pupae buried at depths below one centimetre. Conversely, P. vindemmiae exhibited a greater competitive ability, being more likely to emerge from pupae co-parasitised by S. endius, regardless of oviposition interval or sequence. Our findings suggest that these two parasitoid species coexist through niche differentiation. Our findings also indicate that to increase the effectiveness of biological control, the environmental conditions and risk of interspecific competition should be considered when selecting parasitoid species for release.

在自然界中，竞争物种通常通过生态位分化来实现共存。我们研究了Pachycrepoideus vindemmiae和Spalangia endius（膜翅目：Pteromalidae）的这种现象，这两种蛹寄生物被认为是家蝇的生物控制剂，家蝇（双翅目：Muscidae）。我们检查了每个物种单独和组合在三种类型的基质（沙子、干麦麸和花蝇饮食）中定位埋在不同深度（0、1、2、4 和 6 厘米）的寄主蛹的能力）。然后，我们通过先让一个物种，然后让另一个物种在彼此相隔不到 2 小时到 96 小时的时间段内寄生宿主个体来评估每个物种的竞争力。Spalangia endius表现出比P. vindemmiae更大的定位埋在 1 厘米以下深度的寄主蛹的能力。相反，P. vindemmiae表现出更强的竞争能力，无论产卵间隔或顺序如何，都更有可能从与S. endius共寄生的蛹中出现。我们的研究结果表明，这两种寄生物种通过生态位分化共存。我们的研究结果还表明，为了提高生物控制的有效性，在选择释放的寄生蜂物种时应考虑环境条件和种间竞争的风险。