Developmental niche construction in necrophagous larval societies: Feeding facilitation can offset the costs of low ambient temperature

This study explored the trade-offs between thermal regulation and aggregation, two key factors impacting blow fly (Diptera: Calliphoridae) larvae development. Recent works have demonstrated that necrophagous maggots engage in developmental niche construction, which provides adaptive benefits. First, each species has a preferential temperature, at which larvae grow fast and efficiently. Second, larvae are attracted by each other and aggregate in large maggot masses. These groups modify the local environment and facilitate the exodigestion process (niche construction by perturbation). However, aggregation and relocation towards thermal preferendum are not always compatible under field conditions, forcing larvae to make choices. To test the developmental consequences of such trade-offs, 40 or 80 Lucilia sericata larvae were placed on a thermal gradient (from 22 to 48 degrees C) with or without a captive aggregate of 40 larvae located at 22 degrees C, and their development speed, size and survival were measured. A previous study showed that in such situation the free larvae alone relocated at 33 degrees C, while in the presence of captive larvae they gathered with the captive group at 22 degrees C. In the present developmental study, we observed that such 22 degrees C aggregated larvae actually grew as fast as if they were at 33 degrees C. This result shows that niche construction, here resulting from larval gregarism and feeding facilitation, can compensate for the physiological costs of low ambient temperature. This finding confirms that aggregation of necrophagous Diptera larvae is an efficient adaptation to the carrion environmental constraints and highlights the adaptive value of developmental niche construction.