Almost no written information exists on adult cycling and flight timing of stiletto flies (Diptera: Brachycera: Asiloidea: Therevidae) or window flies (Scenopinidae). This fact is disturbing because of the important role stiletto flies, in particular, play in ecosystem dynamics and population regulation of soil-dwelling arthropods. On the one hand, adult stiletto flies are often abundant at certain times of the year and quite vulnerable to larger predaceous invertebrates and vertebrates. Adults can travel considerable distances in search of water in xeric environments; a few species also imbibe nectar and insect secretions. Stiletto fly larvae, on the other hand, are voracious predators of fossorial insects within sandy substrates and leaf litter. Because of their abundance and ravenous habits, these larvae are excellent regulators of most subterranean phytophagous and saprophytic arthropods and are an extremely important component of nearly all arid and semiarid ecosystems.