Larval Feeding on Bt Hybrid and Non-Bt Corn Seedlings by Harmonia axyridis (Coleoptera: Coccinellidae) and Coleomegilla maculata (Coleoptera: Coccinellidae)

• Published in: Environmental entomology 2008-04, Vol.37 (2), p.525-533
• Main Authors: Moser, Susan E, Harwood, James D, Obrycki, John J
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Animal, plant and microbial ecology; Animals; Applied ecology; Bacillus thuringiensis; Bacterial Proteins - genetics; Bacterial Proteins - pharmacology; Behavior; Biological and medical sciences; body size; Coleomegilla maculata; Coleoptera - drug effects; Coleoptera - physiology; corn; Cry1Ab endotoxin; dietary mixing; Ecotoxicology, biological effects of pollution; Effects of pollution and side effects of pesticides on protozoa and invertebrates; Endotoxins - genetics; Endotoxins - pharmacology; feeding behavior; Feeding Behavior - drug effects; Feeding Behavior - physiology; Fundamental and applied biological sciences. Psychology; Genetic engineering applications; Genetics and breeding of economic plants; Harmonia axyridis; Hemolysin Proteins - genetics; Hemolysin Proteins - pharmacology; hybrids; Insect Control; insect development; Larva - drug effects; Larva - physiology; larvae; mortality; nontarget organisms; Plant breeding: fundamental aspects and methodology; Plant Leaves; seedlings; transgenic plants; Zea mays; Zea mays - genetics; zoophytophagy
• ISSN: 0046-225X; 1938-2936
• DOI: 10.1603/0046-225X%282008%2937%5B525%3ALFOBHA%5D2.0.CO%3B2

Zoophytophagy is an omnivorous activity that occurs when a primarily carnivorous species feeds on plant material. Plant feeding by beneficial predators may have negative consequences if the plant material has been chemically treated, contains toxins, or was transgenically altered. Although common in predaceous Hemiptera, zoophytophagy has been rarely studied in aphidophagous coccinellids. This study examined the likelihood of feeding on Bt and non-Bt corn seedlings by third- and fourth-instar coccinellid larvae, the regularity of feeding events by fourth instars, and the effect of leaf feeding on development time and adult size. Both third- and fourth-instar Harmonia axyridis Pallas and Coleomegilla maculata DeGeer consume leaf tissue, with fourth instars being significantly more likely to feed on corn seedlings. C. maculata larvae ingested leaf tissue more frequently than H. axyridis. Furthermore, when given access to corn seedlings daily, development time of fourth-instar C. maculata increased after Bt hybrid corn treatments compared with non-Bt corn treatments. Zoophytophagous feeding behavior is thought to sustain predators during times of low prey availability, and leaf tissue feeding by coccinellids has typically been attributed to their need for water. However, in this study, tissue feeding regularly occurred even though coccinellid larvae had constant access to water and a daily ad libitum supply of aphids. We suggest that, in addition to environmental conditions, the physiological state of the zoophytophagous species will influence the probability of plant feeding.