Optimizing Fecundity in Zophobas atratus (Coleoptera: Tenebrionidae): Effects of Temperature, Photoperiod, Humidity, and Oviposition Substrate

The giant mealworm, Zophobas atratus (Coleoptera: Tenebrionidae), is a promising insect for food and feed production, but environmental and substrate requirements for adult oviposition remain insufficiently defined. To establish foundational data for mass rearing of Z. atratus , this study evaluated fecundity and adult survival across temperature, photoperiod, and relative humidity (RH) treatments and assessed oviposition‐site use. Newly emerged or 7‐day‐old adults were evaluated at four temperatures (25°C, 27°C, 30°C, and 33°C), under three photoperiods (9L:15D, 12L:12D, and 15L:9D), or at three RH levels (50%, 65%, and 80%); filter paper and wheat bran were compared as oviposition substrates. Fecundity, adult mortality, and substrate‐specific oviposition proportions were quantified over the observation periods. Temperature significantly affected fecundity: mean daily fecundity over 120 days was highest at 30°C (27.3 ± 27.1 eggs/female/day) and lowest at 33°C (5.2 ± 9.7; p < 0.0001), while cumulative fecundity reached 700.9 ± 441.4 and 91.7 ± 76.6 eggs/female, respectively. For the photoperiod treatments, cumulative fecundity at Day 100 was highest under 15L:9D (674.0 ± 173.4 eggs/female) and lowest under 12L:12D (226.7 ± 135.0). For RH, cumulative fecundity at Week 16 was highest at 65% RH (536.8 eggs/female) and final cumulative mortality was lowest (38.3%). Oviposition‐site use shifted: Eggs were deposited predominantly on filter paper early, whereas deposition in wheat bran increased later. Within the tested ranges, 30°C, 15L:9D, and 65% RH independently supported the greatest oviposition performance. These findings provide stage‐specific benchmarks for adult breeder management and oviposition‐system design in large‐scale Z. atratus rearing.