Date of Award:
5-1-1997
Document Type:
Thesis
Degree Name:
Master of Science (MS)
Department:
Biology
Committee Chair(s)
Edward W. Evans
Committee
Edward W. Evans
Committee
Frank J. Messina
Committee
John M. Stark
Abstract
Ladybird beetles (Coccinella spp.) are important predators of pea aphids (Acyrthosiphon pisum) in alfalfa. Adult ladybird beetles also consume alternative foods such as alfalfa weevil larvae (Hypera postica) and nectar. I compared egg production and ovariole condition of Coccinella septempunctata (an Old World species introduced to North America) and Coccinella transversoguttata (an indigenous North American species) that were maintained on diets of pea aphids, alfalfa weevil larvae, sugar water ("artificial nectar"), or various combinations of these foods. In the first experiment, gravid females of both species continued to lay many eggs and had large ovarioles when maintained on a diet of pea aphids, but they stopped laying eggs and had small ovarioles when maintained on a diet of alfalfa weevil larvae. The second experiment included six pea aphids supplied daily + weevil larvae in addition to each prey alone. Females maintained on this diet produced more eggs than females fed weevil larvae only, but fewer eggs than females fed large numbers of aphids. In the third experiment, females of Coccinella septempunctata (but not Coccinella transversoguttata) produced more eggs when an aphid diet was supplemented with alfalfa weevil larvae. In the fourth, fifth, and sixth experiments, females maintained on sugar water stopped laying eggs and had small ovarioles. However, when sugar water was supplemented with weevil larvae, egg laying continued and ovarioles were large. In the seventh experiment, overwintered females of Coccinella septempunctata began laying eggs when provided both sugar water and weevil larvae, but did not lay eggs when provided only one of these foods. These results indicate that alfalfa weevil larvae should be considered as "alternative" prey with the additional benefit of enhanced reproduction with low aphid numbers and an interaction with nectar and/or sugar water to stimulate reproduction for Coccinella septempunctata and Coccinella transversoguttata. Consumption of this alternative prey by ladybird beetles may contribute to biological control of both pea aphids and the alfalfa weevil itself.
Recommended Citation
Richards, Douglas R., "The Role of Alfalfa Weevil Larvae as Prey in Adult Maintenance and Reproduction by Two Ladybird Beetle Species" (1997). Biology. 645.
https://digitalcommons.usu.edu/etd_biology/645
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