Water, Feeding Efficiencies, and Development of Dermestes maculatus DeGeer (1774)

Although dermestids have varying ecological roles, most Dermestes are generally associated with decomposition of dry animal tissues. However, Dermestes maculatus DeGeer (1774) can eat soft, hydrated tissues, so it is unclear if the apparent preference of Dermestes maculatus for dry tissue reflects physiological adaptation or competitive exclusion by blowflies and other invertebrate scavengers that arrive at carrion earlier and may have faster immature development rates. To address this question, we examined development of D. maculatus larvae on hydrated and dry food, and we determined development rates at a constant temperature of 25°C. Specifically, we conducted multiple replicated experiments in incubators. Initial experiments used with a factorial treatment arrangement of food type (wet versus dry) and larval density (1, 5, 10, 15, and 25 per 5 g of food) with 4 replications. Additionally, for dry food we determined growth, consumption, and conversion rates for 3-6 stage larvae, and consumption and conversion rates for adults. Hydrated food significantly reduced survivorship of D. maculatus larvae and adults (ca. 20% survivorship) as compared to dried food with survivorship rates of ca. 80-90%. Adults feeding on hydrated food were observed to void water, likely to overcome problems with osmotic regulation. Given dry food with little water and high conversion rates (much greater than 10%) in larvae, evidence indicated D. maculatus obtains most water metabolically and not through diet. These adaptations indicate that D. maculatus (and likely related species) have evolved physiologically to exploit dry carrion thereby avoiding competition with other carrion-feeding species. However, D. maculatus is not adapted for low humidity environments or to avoid extreme water loss, these adaptations allow use of a unique resource but do not represent adaption to xeric conditions generally. Moreover, the very adaptations that allow D. maculatus to survive on dry food, are potentially lethal when only hydrated food is available.