The variation in instar number and the pattern of sequential instar development time of Tenebrio molitor L. (Coleoptera: Tenebrionidae) was studied under 4 different diet regimes. Addition of dietary supplements consisting of dry potato or a mix of dry potato and dry egg whites significantly reduced the number of larval instars and total development time. The pattern of sequential stadia length showed regularity and low variability in instars 5 - 9. Stadia length continuously increased between instar 10 and the last instar before pupation (P−1). Instar number significantly impacted total development time and was also significantly correlated with stadia length. The length of the 1st, 2nd, 3rd, and 4th stadia was not significantly affected by diet indicating that they may represent a stable part of the life cycle of T. molitor. The length of the last stadium (P−1) was regular within food treatments regardless of sequential instar number, but P−1 was also significantly affected by nutrition in a similar way...

We studied the ability of Tenebrio molitor L. (Coleoptera: Tenebrionidae) to self-select optimal ratios of two dietary components to approach nutriti

Crowding conditions of larvae may have a significant impact on commercial production efficiency of some insects, such as Tenebrio molitor L. (Coleoptera: Tenebrionidae). Although larval densities are known to affect developmental time and growth in T. molitor, no reports were found on the effects of crowding on food utilization. The effect of larval density on food utilization efficiency of T. molitor larvae was studied by measuring efficiency of ingested food conversion (ECI), efficiency of digested food conversion (EDC), and mg of larval weight gain per gram of food consumed (LWGpFC) at increasing larval densities (12, 24, 36, 48, 50, 62, 74, and 96 larvae per dm²) over four consecutive 3-wk periods. Individual larval weight gain and food consumption were negatively impacted by larval density. Similarly, ECI, ECD, and LWGpFC were negatively impacted by larval density. Larval ageing, measured as four consecutive 3-wk periods, significantly and independently impacted ECI, ECD, and LWGpFC in a negative way. General linear model analysis showed that age had a higher impact than density on food utilization parameters of T. molitor larvae. Larval growth was determined to be responsible for the age effects, as measurements of larval mass density (in grams of larvae per dm²) had a significant impact on food utilization parameters across ages and density treatments (in number of larvae per dm²). The importance of mass versus numbers per unit of area as measurements of larval density and the implications of negative effects of density on food utilization for insect biomass production are discussed.

The house cricket, Acheta domesticus L. (Orthoptera: Gryllidae) is one of the most important species of industrialized insects in the United States. Within the past five years the market of cricket powder as a food ingredient has been growing with increasing consumer interest on more sustainable sources of food. However, high labor costs of cricket production and high prices of cricket feed formulations result in cricket powder market prices much higher than other protein-rich food ingredients, making cricket powder only competitive within the novelty food market. In this study new diets formulated using by-products were developed using dietary self-selection followed by regression analysis. Crickets selected among seven different combinations of ingredients. Consumption ratios of food ingredients and by-products were used to determine macro and micro-nutrient intake. Regression analysis was used to determine the individual nutrient intake effect on cricket biomass production. Intake of vitamin C, sterol, manganese, and vitamins B₁ and B₅ had the most significant impact on live biomass production. Four diets were formulated based on this information and compared with a reference (Patton’s 13) and a commercial diet. Although, crickets reared on Patton’s diet 13 produced the most dry-weight biomass and developed the fastest, diet 4 (consisting of 92% by-products) generated the most profit (with a cost of $0.39 USD per kg) after an economic analysis that did not include the commercial formulation. Dry-weight biomass production was not significantly different among the four new diets and the commercial diet. This study demonstrated the value of dietary self-selection studies in developing oligidic insect diets and in studies of insect nutrition. This is the first such study involving farmed edible crickets and agricultural by-products. Four new cricket diet formulations contain between 62 and 92% agricultural by-products are included.

The impact of adult weight, age, and density on reproduction of Tenebrio molitor L. (Coleoptera: Tenebrionidae) was studied. The impact of adult weight on reproduction was determined by: (1) counting the daily progeny of individual adult pairs of known weight and analyzing the data with linear regression and (2) creating 5 weight classes of 10-mg intervals starting at 60 mg (60 - 69.9mg) and ending at 100 mg (100 - 109.9 mg), then the progeny of 10 groups of 5 males and 5 females of each weight class were compared using ANOVA. To determine the impact of adult density on reproduction, adults were grouped at 8 different densities by increasing numbers per box (at 1:1 sex ratio). Weekly progeny production of 8 groups per density treatment was compared using ANOVA. There was no significant relationship between female weight and progeny production in the individual pair analysis. Fecundity was significantly different among weight classes, but the relationship was not linear. Adult density had a signif...

Nutrient self-selection was used to determine optimal intake ratios of macro-nutrients by Tenebrio molitor L. larvae. Self-selection experiments consisted of 9 combinations (treatments) of 8 ingredients, from a total of 20 choices, radially distributed in a multiple-choice arena presented to groups of 100 T. molitor larvae (12th–13th instar). Larvae freely selected and feed on the pelletized ingredients for a period of 21 days at 27 °C, 75% RH, and dark conditions. Consumption (g) of each ingredient, larval live weight gained (mg), and frass production were recorded and used to calculate food assimilation and efficiency of conversion of ingested food. The macro-nutrient intake ratios were 0.06 ± 0.03, 0.23 ± 0.01, and 0.71 ± 0.03 for lipid, protein, and carbohydrate, respectively on the best performing treatments. The intake of neutral detergent fiber negatively impacted food assimilation, food conversion and biomass gain. Food assimilation, food conversion, and biomass gain were significantly impacted by the intake of carbohydrate in a positive way. Cabbage, potato, wheat bran, rice bran (whole and defatted), corn dry distillers’ grain, spent brewery dry grain, canola meal and sunflower meal were considered suitable as T. molitor diets ingredients based on their relative consumption percentages (over 10%) within treatment.