W. Louis Tedders

Superior efficacy observed in entomopathogenic nematodes applied in infected-host cadavers compared with application in aqueous suspension.

Two greenhouse experiments were conducted to compare the efficacy of entomopathogenic nematodes applied in aqueous suspensions with application in infected cadavers. One experiment targeted the diaprepes root weevil Diaprepes abbreviatus with Heterorhabditis indica and the other targeted the black vine weevil Otiorhynchus sulcatus with H. bacteriophora. Entomopathogenic nematode application in infected cadavers were more effective than nematode application in aqueous suspensions in all cases. The increased efficacy observed in the cadaver applications may have been due to the additional physiological stress in the aqueous application (during temporary storage in water or upon application). Superior efficacy in the cadaver application might also have been due to compounds in the infected host cadaver that can enhance nematode infectivity.

Impact of Adult Weight, Density, and Age on Reproduction of Tenebrio molitor (Coleoptera: Tenebrionidae)

Abstract 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 significant impact on progeny per female and progeny per unit area. Reproductive output per female decreased as adult density increased. Progeny per unit area increased to a maximum at a density of 14 adults/dm2 and then declined sharply. Adult age had a significant impact on reproduction. The highest reproductive output occurred at 2 and 3 wk of age and was significantly higher than at any other age. Adult density and age may be manipulated to maximize production of T. molitor larvae.

Use of Nutrient Self-Selection as a Diet Refining Tool in Tenebrio molitor (Coleoptera:Tenebrionidae)

Abstract A new method to refine existing dietary supplements for improving production of the yellow mealworm, Tenebrio molitor L. (Coleoptera: Tenebrionidae), was tested. Self-selected ratios of 6 dietary ingredients by T. molitor larvae were used to produce a dietary supplement. This supplement was compared with existing supplement formulations mixed with wheat bran at 1:4 ratio and a control consisting of wheat bran alone for food utilization efficiency, larval growth, development time, immature survival, and fecundity. Ingredients of dietary supplements included dry potato as a source of carbohydrate; dry egg white and soy protein as a source of protein and; peanut, canola, and salmon oil as a source of lipid. A supplement consisting of dry potato alone significantly improved food utilization, growth, development time, survival, and fecundity compared with the wheat bran-only control group. The addition of protein to the supplement significantly shortened development time and improved food conversion efficiency and fecundity compared with the supplement with potato alone. The addition of lipid did not provide any significant improvements. The supplement derived from self-selected ratios of the basic ingredients provided a significant increase in fecundity compared with previously developed supplements and the control. Self-selected ratios of the basic ingredients by T. molitor larvae had an effect on the adult stage that resulted in significantly higher progeny production.

Morphometric Analysis of Instar Variation in Tenebrio molitor (Coleoptera: Tenebrionidae)

ABSTRACT Measurements of head capsule, mandible, metanotum, and body weight were done on larvae of Tenebrio molitor L. (Coleoptera: Tenebrionide) from the second to the last instar. Instar number varied from 14 to 18, but 15 or 16 instars were the most common. The value of dimensional measurements was evaluated as a tool for instar determination and to improve understanding of instar variation in T. molitor. Three methods of analysis were used, including discriminant, cluster, and frequency distribution analyses. Stepwise regression analysis was used to determine the optimal combination of dimensional variables. Head capsule width, left mandible length, and body weight at the beginning of stadia were the most significant variables impacting instar. Discriminant analyses of instar using these three variables resulted in 47.74% misclassifications, indicating a high degree of dimensional overlapping among instars. Dimensional overlap and variability increased in older instars. Cluster 15-group analysis using measurements of head capsule width and mandible length resulted in the lowest level of group variability; however, there was low degree of correspondence between cluster groups and instars. Frequency distribution analysis of head capsule width revealed 11 peaks, but only the early 8 peaks corresponded with observed instars. All three methods of morphometric analysis failed to identify all instars of T. molitor correctly. Frequency distribution analysis provided the best match, but only among instars 2 to 10. It appears that instar variation in the larval development of T. molitor occurs after the 10th instar. A model of T. molitor developmental plasticity is proposed.