Flytraps and Their Operation [1930]

In Short

First published in 1916 and revised in 1930, this United States Department of Agriculture bulletin is an explicit technical manual detailing the design, construction, and deployment of large-scale mechanical flytraps. Entomologist F. C. Bishopp outlines the behavior of distinct fly species, providing exact specifications for building low-cost screen-and-hoop traps, window interceptors, and modified manure boxes. It has endured as an archetype of early twentieth-century applied entomology, demonstrating how plain materials, accurate geometric construction, and precise chemical baiting can solve widespread agricultural and public health threats without complex machinery.

The Story

The work functions as an authoritative guide to environmental sanitation and pest suppression, systematically building from basic biological principles to large-scale rural deployment. Bishopp opens by defining the proper role of mechanical trapping within a comprehensive sanitary program. Traps do not replace the primary task of eliminating breeding grounds like manure piles and decaying refuse, but they serve as essential interceptors. They catch flies traveling from unsanitary neighboring sites, capture survivors of chemical treatments, and provide an accurate measurement of how well local sanitation efforts are working.

The narrative shifts to the behavioral mechanics of the pests themselves. Bishopp divides annoying flies into species that breed strictly in decaying animal matter—such as blowflies and the destructive screw-worm fly—and those that breed in both animal and vegetable matter, dominated by the common house fly. Because flies naturally feed according to odor preferences and escape upward toward light, effective trapping relies on a universal mechanical design: a wide outer entrance leading into an inner screen cone with a narrow top aperture, drawing insects into a brightly lit cage from which they cannot figure out how to escape.

To make these tools accessible to any farmer or livestock owner, Bishopp provides step-by-step assembly instructions for the conical hoop trap, a two-foot-tall wire cylinder built from cheap wooden barrel hoops, laths, and screen wire. He supplies exact geometric instructions for drafting and cutting the internal screen cone using a carpenter's square and dividers. Variations follow, including simplified wire-top models, all-metal galvanized iron traps built for harsh range conditions in the Southwest, window-mounted traps designed to catch flies entering or leaving barns, and specialized screen covers integrated directly into concrete or wooden manure storage pits.

The final phase of the book details operational maintenance and chemical attractants. House flies require fermenting mixtures like blackstrap molasses, sour milk, or bran mash, while blowflies and screw-worm flies demand animal tissue, such as rabbit carcasses, slaughterhouse "gut slime," or reconstituted dried egg. To prevent meat baits from becoming breeding grounds themselves, Bishopp instructs readers to add nicotine sulphate to the bait pans. The treatise concludes with specific rules for trap placement in midday shade or sunlight, weekly emptying routines using sulfur smoke or hot water, and a short, low-cost recipe for homemade sticky paper.

How It Unfolds

Establishing the strategy Bishopp introduces trapping as an indispensable supplement to breeding-site sanitation, warning that trapping must start early in the spring to prevent massive midsummer population booms.

Understanding the target The text classifies target species by their feeding and breeding habits, noting that house flies seek fermenting vegetable matter while blowflies and screw-worm flies are drawn exclusively to animal decay.

Engineering the conical trap Detailed instructions outline how to construct an 18-inch-diameter screen cylinder using wooden barrel hoops, laths, and a central screen cone crafted via precise geometric formulas.

Adapting for specialized uses The guide presents alternative structural designs, including heavy-duty, all-metal traps for western livestock ranges, window-frame interceptors for dairy barns, and sealed manure-box traps that prevent emerging flies from escaping storage pits.

Formulating effective baits Bishopp lists tested attractant mixtures tailored to specific pests, ranging from cheap molasses solutions and fermented milk for house flies to slaughterhouse intestinal linings and nicotine-treated meats for range blowflies.

Maintaining field operations The final section governs daily maintenance, detailing optimal trap placement out of strong winds, weekly clearing methods using sulfur fumes or scalding water, and basic procedures for constructing sticky fly papers.

The People

F. C. Bishopp As the Principal Entomologist in Charge of the Division of Insects Affecting Man and Animals, Bishopp is the authoritative voice of the manual. He seeks to eradicate agricultural losses and public health risks through methodical, low-cost engineering. He stands against public over-reliance on single remedies and improper trap maintenance, insisting on rigorous adherence to geometric construction and sanitation standards.

C. F. Hodge An inventive entomological researcher featured in the text, Hodge designs specialized interceptive structures. He introduces the window-mounted fold trap and the garbage-can trap, aiming to capture flies at specific entry and exit points of structures before they can reach food or stock.

E. W. Laake and D. C. Parman Field researchers within the Bureau of Entomology who conduct extensive testing on trap durability and efficiency. Laake helps perfect the standardized conical hoop trap, while Parman simplifies the design by eliminating wooden tops in favor of crimped wire rims that farmers can build faster with fewer tools.

Arthur Swaim and R. H. Hutchison Innovative developers cited for their contributions to manure management. Swaim creates a removable screen-tent trap system for manure pits, while Hutchison devises a specialized maggot trap platform that captures larvae as they migrate out of manure piles.

In Its Own Voice

"There is a general tendency, however, for those engaged in combating flies to put too much dependence on the flytrap as a method of abating the nuisance."

Bishopp opens his instructions by framing mechanical traps as secondary tools that must always be combined with primary sanitation.

"Under no condition should the sides or top of the trap be of solid material, as the elimination of light from the top or sides has been found to decrease the catch from 50 to 75 per cent."

The manual emphasizes how fundamental insect light-seeking behaviors dictate every structural requirement of the cage.

"During the latter half of one season over 100 gallons of flies, the vast majority of which were screw-worm flies, were captured in about 25 traps operated on a ranch in west Texas."

Field evidence highlights the immense volume of pests that properly maintained range traps can remove from livestock pastures.

What It's Really About

Beneath its practical construction diagrams, Flytraps and Their Operation is a study in applied biological control and resourcefulness. It argues that effective pest management does not require expensive technology or commercial chemicals, but rather a clear understanding of insect behavior. By exploiting a fly's natural drive to fly toward light and seek out active fermentation odors, a farmer can turn scrap lumber, wire netting, and barrel hoops into an efficient sanitation system.

The text also addresses the broader agricultural issue of self-reliance. It emphasizes that rural communities can protect livestock health, safeguard dairy sanitation, and curb destructive pests like the screw-worm fly through localized, preventive measures rather than reactive, costly interventions.

Why Read It Today

This short agricultural bulletin will appeal to modern homesteaders, woodworkers, historians of science, and readers fascinated by early twentieth-century ingenuity. Reading Bishopp’s work offers a distinct satisfaction: it is clean, intensely practical prose stripped of any corporate fluff or academic posturing. Every paragraph exists to deliver usable knowledge, whether calculating the arc of a screen cone with a framing square or balancing bait recipes for maximum active fermentation.

While the bulletin reflects the plain, unadorned style of a 1930s government publication—complete with rigid imperial dimensions, chemical recommendations like nicotine sulphate, and references to slaughterhouse byproducts like "gut slime"—its fundamental physics and geometry remain completely sound. What stays with the reader is a sense of functional clarity. Bishopp shows how simple materials, guided by an understanding of animal behavior, can solve severe environmental problems.