Masters Theses

Date of Award

3-1988

Degree Type

Thesis

Degree Name

Master of Science

Major

Entomology and Plant Pathology

Major Professor

Paris L. Lambdin

Committee Members

Reid R. Gerhardt, Charles D. Pless

Abstract

Basic biological research on systematics and life histories of predators and parasitoids is essential for successful implementation of an integrated pest control program. Coccophagus lycimnia (Walker) may prove to be a useful biocontrol agent of the brown soft scale Coccus hesperidum (L.); however, little of its biology is known. The objective of this study was to describe the immature stages of female C. lycimnia and determine the longevity, fecundity, and optimal host length for oviposition by adults. Additionally, adult C. lycimnia were redescribed to aid in species identification.

Brown soft scales were used as hosts for C. lycimnia. The scales were reared on watermelon, Citrullus vulgaris Schrader, to obtain large populations for subsequent testing. Bird's nest ferns, Asplenium nidus L., were used as hosts for the brown soft scale when conducting tests with C. lycimnia.

Previous descriptions of C. lycimnia and its synonyms were based primarily on differences in color. Since color variability of this species may have led to its many synonyms, a redescription of C. lycimnia was conducted. Measurements and descriptions of 160 characters were analyzed using correlation coefficients and coefficients of variation. Characters with low coefficients of variation and high correlation coefficients were used as possible characters for species separation, since other species of Coccophagus were unavailable for comparison.

The optimum size of C. hesperidum for parasitism by C. lycimnia ranged between 1100 to 1500μm long. Parasitized scales continued to develop.

Mated females of C. lycimnia oviposited an average of six eggs per day, and lived an average of thirteen days. Superparasitism occurred in 9.3% of the scales dissected.

Virgin day-old females and males of C. lycimnia were tested at three temperatures (17, 22, 27°C) and two dietary supplements (water, honey and water). Females lived longer than males at all temperature and dietary regimes. Longevity increased as temperature decreased regardless of dietary supplements. Longevity increased when parasitoids were given honey and water as a dietary supplement instead of water alone.

Immature females of C. lycimnia were described and illustrated. There were three instars which were distinguished by mandible length and width, head capsule width, and absence or presence of spiracles. The unusually long duration of 1st instars, and the occurrence of a pupal sheath were discussed. Development from egg to adult was completed in an average of 21 days.

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