Date of Award:

5-1-1985

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Biology

Department name when degree awarded

Biology Ecology

Committee Chair(s)

B. Austin Haws

Committee

B. Austin Haws

Committee

D.W. Davis

Committee

K.H. Asay

Abstract

The growth and development of the black grass bug Labops hesperius Uhler was observed to be a definitive process highly correlated with the accumulation of thermal energy units; chill units and growing degree hours. Development of a laboratory model demonstrated that there were considerable variations due to abiotic and biotic factors in the field that resulted in the field to laboratory growing degree hour and chill unit ratios to average about 0.55, with a base temperature of 4.5 C. Chill requirements to break egg diapause in 90 percent of the grass bug eggs tested required 1100 chill units in the field and 600 in the laboratory. Calendar observations showed that chill requirements were usually complete by the end of December. Egg development in the laboratory correlated with growing degree hour accumulation in three discontinuous developmental cycles after 3692 growing degree hours. The laboratory to field growing degree hour ratio for eclosion was 0.568. Nymphal development was highly correlated with growing degree hour accumulation with r2= 0.982. Growth and development of body parts, stage and growing degree hours showed average correlations > 0.9. Sexual dimorphism was evident in nymphal head capsule widths at the fourth instar. Ninety percent of the nymphs in the laboratory became adults after 8991 growing degree hours after eclosion. The field to laboratory ratio of growing degree hours required for the maturation of adults was estimated at 0.541. Mating was observed one week after the final molt, with oviposition occurring one week later. The biological reproductive capacity was measured at 48 eggs per female. The composition at maturity of the wild population studied was calculated at 60 percent male and 40 percent female. As the season progressed, female numbers continuously increased until they comprised more than 95 percent of the population at the end of the cycle. Improved rearing techniques including controlled humidity levels improved grass bug survival when reared in the laboratory. Two new parasites of adult black grass bugs were discovered, a mermithid worm and a dipterous larva, both of which were found only in female grass bugs. Models and correlations developed during this study should be of great value to integrated interdisciplinary pest xvi management of black grass bugs.

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