Date of Award:

8-2022

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Biology

Committee Chair(s)

Ricardo A. Ramirez

Committee

Ricardo A. Ramirez

Committee

Theresa L. Pitts-Singer

Committee

J. Earl Creech

Abstract

Alfalfa is one of the most economically important crops in North America. To produce alfalfa seed, a pollinator must release plant reproductive organs by applying pressure to keel petals. The alfalfa leafcutting bee, Megachile rotundata, is the primary commercial pollinator of alfalfa. U.S. bee managers struggle to maintain populations due to many mortality factors. One cause is attack from parasitoid wasps such as Melittobia acasta. Females can lay hundreds of eggs and have multiple generations, which can decimate bee stocks. Chapter Two investigates the life cycle and base temperature that allows development of M. acasta on bee hosts. In each of 20 vials, I exposed four bee larvae (prepupae) to several wasps and kept them at 30°C. Wasp progenies were observed daily until death. I described 12 distinct life stages, and adult wasps emerged in 16 to 20 days. I also raised M. acasta from eggs to adults along a temperature gradient bar. Statistical analysis revealed the minimum temperature for development was 8.5°C and that development from egg to adult averaged 305.8-degree days. Chapter Three determined the M. rotundata life stages upon which wasps lay eggs and offspring survive. I also determined M. acasta female survival on resources found in bee nests (an empty cell, a provision mass with and without a bee egg, and a bee prepupa). Each nest resource was exposed to a wasp (replicated 40 times). Wasps survived an average of 5, 8, and 34 days on an empty cell, either mass provision, and the bee prepupa, respectively. I also exposed 40 replicates of bee larvae and each of the pupal stages to 10-20 wasps. Wasps laid eggs on bee prepupae and their offspring developed to adulthood, while offspring from eggs laid on pupae usually died. This showed that if a wasp emerged in the field, it could live long enough for newly developed bee prepupae to serve as hosts. This research helps in understanding leafcutting bees as hosts, alert M. acasta biology when using alfalfa s bee managers to the need for controlling these wasps during bee incubation and supports future development and application of management strategies.

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