Pollens of Fabaceae and Poaceae Alone or Combined with Honey Solution? Suitable Diet for Adults of Chrysoperla externa (Hagen) (Neuroptera: Chrysopidae).

Abstract

The main source of proteins for adult Chrysoperla externa (Hagen) is pollen, the content of which varies among species and may have different effects on the adult biology. In the laboratory, we evaluated the suitability of pollens from Canavalia ensiformis (JB), Crotalaria juncea (SH) (both Fabaceae), Pennisetum glaucum (MI), Sorghum bicolor (SO), and Zea mays (CO) (all Poaceae), alone or as mixtures of pollen from one species of each family, for the performance of adult C. externa; these diets were compared to brewer's yeast + honey (standard diet), 50% honey solution and water alone. Excluding water, the diets were supplemented with an extra honey solution (EHS). The protein content was used as a measure of diet quality, although the carbon and mineral contents were also evaluated. The diets combined with EHS significantly improved adult longevity. All the pollen diets promoted egg production. The CO-alone, SO-alone, JB-alone, SH-alone, SO + JB, CO + SH, MI + SH and SO + SH mixtures resulted in reproduction rates similar to those observed with the standard diet, indicating their suitability for C. externa. In contrast, the effects of MI-alone, MI + JB and CO + JB on reproduction were significantly worse than those of the standard diet. In terms of nutritional value, SH was the pollen enriched in protein, CO, MI and SO were protein-poor pollens, and the JB and dipollen mixtures presented intermediate levels. In conclusion, in contrast to our expectations, a mixture of Fabaceae and Poaceae pollens generally is not nutritionally superior to each pollen alone for improving the performance of adult C. externa.