Diets of ladybird beetles (Coleoptera: Coccinellidae) in Utah alfalfa fields

2008 2008

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Abstract (summary)

Aphidophagous lady beetles rely on multiple sources of food in their environment. Alfalfa fields provide both aphids and many alternate foods, such as other arthropod prey, pollen, and fungi. Alfalfa fields ( Medicago sativa L.) in Utah have low aphid densities, which may require lady beetles to consume alternative sources of food. Many methods can be used to determine these diets; frass analysis is used here to compare the diets of the introduced species Coccinella septempunctata L. with two native species, C. transversoguttata richardsoni Brown and Hippodamia convergens Guérin-Méneville, that occur in the Utah alfalfa habitat.

In initial laboratory experiments to examine the feasibility of frass analysis, 48 hours at 20°C was sufficient time for adult lady beetles to pass prey cuticle through their guts. When consumed by these adults, pea aphids (Acyrthosiphon pisum [Harris]), alfalfa weevil larvae (Hypera postica [Gyllenhall]), and C. septempunctata larvae produced distinctive fragments in the frass. Such fragments could also be distinguished in frass collected in a field experiment in which aphid densities in plots of alfalfa were manipulated. Furthermore, additional consumed foods could be distinguished in the field experiment, including pollen, fungi, and other types of arthropods.

Frass analysis demonstrated higher use of aphid prey by C. septempunctata adults collected from high versus low aphid density plots during the field experiment. Use of other types of prey, such as alfalfa weevil larvae, other arthropods, pollen and fungi, was similar between plots with high and low aphid densities. A field census was performed over two years to track the diets of the three species of lady beetles during the first crop of alfalfa, when two sources of prey in particular were present, aphids and alfalfa weevil larvae. Comparisons of diets revealed that the three species utilized different types of prey to similar degree during both years. In general, however, higher percentages of C. septempunctata adults were found to have consumed aphids and weevils during both years. Also, C. septempunctata was found to produce more frass and consume larger quantities of prey than either native species during the second year.

Indexing (details)

0353: Entomology
Identifier / keyword
Biological sciences; Aphidophagous; Coccinella septempunctata; Coccinella transversoguttata; Hippodamia convergens; Ladybird beetles; Polyphagous
Diets of ladybird beetles (Coleoptera: Coccinellidae) in Utah alfalfa fields
Davidson, L. Nicole
Number of pages
Publication year
Degree date
School code
MAI 47/01M, Masters Abstracts International
Place of publication
Ann Arbor
Country of publication
United States
Evans, Edward W.
Committee member
Alston, Diane G.; Whitesides, Ralph E.
Utah State University
University location
United States -- Utah
Source type
Dissertations & Theses
Document type
Dissertation/thesis number
ProQuest document ID
Database copyright ProQuest LLC; ProQuest does not claim copyright in the individual underlying works.
Document URL
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