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United States Department of Agriculture

Agricultural Research Service

James R. Hagler
Research Entomologist

1 - Biography
2 - Key Publications
3 - Learn More About My Research
Learn More About My Research

Mission Statement:

The WCRL's Predator Biology Unit is dedicated to the study of both fundamental and applied aspects of predator biology. We are using state-of-the-art molecular techniques to examine the natural enemies of the whitefly, pink bollworm and lygus. Our goals are to (1) identify indigenous predators of these key pests and (2) to evaluate the efficacy of augmentative biological control agents. Currently, we are examining differences in the feeding behavior between augmented (i.e., domestic) and indigenous predators of whitefly, pink bollworm and lygus.

Predator Mark-Release-Recapture Techniques

A key component in the evaluation of insect predation is the precise monitoring of the beneficials released. Generally, this has been done by marking insects. It is critical that the marker be environmentally safe, inexpensive, persistent, and without negative effect on insect behavior or health. Paint, dye, and tagging procedures are economical and easy to use, but are often ineffective on small insects because they can inhibit normal dispersal or require intensive labor. Elemental marking (i.e., rubidium) is environmentally safe and effective for some insects, but can adversely affect behavior and development of others. Furthermore, trace element marking is costly, generates chemical waste, requires specialized equipment, trained personnel, and extensive sample preparation. In summary, most of the current marking procedures proved to be too labor-intensive, impractical, or costly for my studies. I circumvented these obstacles by developing an insect immunomarking procedure that can be used to mark thousands of predators easily, rapidly, safely, and inexpensively for discrimination between commercially-reared predators and their native counterparts. The retention time of this marker is superior to many marking procedures. I have shown that it is feasible to mark predators with rabbit immunoglobulin G (IgG), a readily available mammalian blood serum protein, then run an ELISA using its complementary antibody (anti-rabbit IgG) while concurrently running ELISAs using the same samples against our pest MAbs to measure for the presence of multiple pest egg antigens (i.e., prey) in an individual predator's gut. In 1994 I field tested the immunomarker and found it to be superior to DayGlo dust marking. Individuals marked with DayGlo appeared "sluggish" while those marked with rabbit IgG showed no adverse effects. Another problem I encountered with DayGlo dust was that it was not visible to the naked eye 12 h after marking. Most of the individuals (>80%) I dusted had to be painstakingly examined under a dissecting microscope to determine if DayGlo was present. Therefore, examining individuals for the presence of DayGlo dust was more time consuming, expensive, and laborious than my marking immunoassay. However, the ultimate usefulness of any marker is that it is reliable. Again, my marking immunoassay proved to be more precise than the DayGlo dust marking procedure.

Given the success of our immunomarking ELISAs, I can now evaluate the feeding (using my gut content immunoassay) and dispersal behavior (using my marking immunoassay) of inundative releases of commercially-reared predators. Furthermore, the more recent discovery that protein marking works well for labeling minute arthropods has resulted in a significant paradigm shift in the way researchers now consider marking small parasitoids, predators, and herbivores for dispersal studies.

For more on our methods that we have developed for studying predation:
It's Gut-Check Time !!! Examining Insect Predators

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Last Modified: 4/28/2008
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