The Nutritional Ecology of Dectes texanus (Coleoptera: Cerambycidae): Does Host Choice Affect the Macronutrient Levels in Overwintering Larvae?

Abstract

Dectes texanus LeConte (Coleoptera: Cerambycidae) is a stem-boring cerambycid that is an agricultural pest of soybean and cultivated sunflower. For D. texanus, cultivated sunflower is thought to be nutritionally superior to soybean and preferred over soybean. This study compared the macronutrient levels in overwintering larvae and the pith of the host plants to determine if soybean is an inferior host. The levels of total protein, total carbohydrates, and total lipids were measured in larvae from sunflower and soybean; larval head capsule width and larval mass also were compared. There were no differences between levels of total protein and total carbohydrates per unit mass between larvae from the 2 hosts; however, larvae from sunflower had significantly higher levels of lipids than larvae from soybean. A comparison of head capsule width indicated that larvae from soybean had significantly larger head capsule widths than those from sunflower, suggesting that soybean-fed larvae were larger or were in a later instar. Larvae from soybean and sunflower did not have significantly different masses, unlike what was found in pupae in previous studies. Soybean pith had significantly higher protein and carbohydrate levels whereas sunflower pith had a significantly higher level of lipids. The results suggest that the nutritional differences between the 2 host plants did affect the nutritional content and possibly growth or development rates in D. texanus before diapause.