Why do no specialized necrophagous species exist among aquatic insects?

Among terrestrial insects, there is a rich guild of specialized necrophagous taxa, i.e., that feed directly on carrion. These organisms constitute a significant functional component of terrestrial ecosystems, and have recently been extensively studied because of their importance in forensic entomology. Nothing similar exists in lotic environments, although paradoxically, insects are the most important group of invertebrates in streams and rivers, where they constitute up to 70 to 90% of benthic communities. We present some hypotheses as to why specialized necrophagous taxa have evolved among terrestrial, but not among aquatic insects. We suppose that the lack of specialized necrophagous aquatic insects was the result of many synergic evolutionary pressures, partly related to the distinctive physical features of lotic environments and partly to processes of competitive exclusion with other closely related arthropods.