[Stinging Insects] The Curious Fantasy of Scarecrow Hornet Nests

The modern environmental movement has spawned a thriving economy devoted to producing goods and services that flaunt their “green” credentials, and one of the most entertaining subcategories is the galaxy of consumer-oriented pest control products that are described as “natural” or “non-toxic.” Some of these are indeed positive steps toward rationality, but all too often they are gimmicks created in cynicism or ignorance that precision-target the biologically unsophisticated. The premier examples of this genre are the innumerable types of gadgets claiming to repel pests by means of some type of invisible energy, many of which are peddled by high-profile and highly trusted brands simply because the business is far too lucrative to ignore merely on the basis of honesty, ethics and all the other inconvenient moral principles.

A less (pseudo) high-tech variation of non-chemical repellents is the scarecrow concept, which assumes a pest species is smart enough to recognize something dangerous, but dumb enough to be fooled by a crude imitation of the real thing. Mannequins placed in fields to unsettle pest birds are probably as old as agriculture itself. Nevertheless, pictorial representations of classic scarecrows often incorporate a few of the feathered vermin perched on the head or limbs, acknowledging that birds quickly learn that the human-like forms are nothing more than static imposters. Scarecrows thus persist mainly as colorful or menacing folk art rather than as a serious attempt to prevent crop damage. Modern incarnations (fake owls, big eye balloons, brightly flashing objects, etc.) similarly lose their effectiveness within hours or days after they are deployed. Such products typify the lion’s share of the green pest control devices marketed in home and garden catalogues, stores and websites. Unlike electronic pest repellers, they are not pure snake oil. The key to promoting them with a straight face is that they are based on at least some biological facts outside of the laboratory and produce some positive results, regardless of how minor or how fleeting.

On the far end of the spectrum, however, is a collection of merchandise that joins “black-box” repellers in representing an exuberant form of pure, unadulterated, quackery. As a practitioner and spokesman for a scientifically based IPM ethos I try to ignore them as best I can, but as an academically trained hymenopterist who has spent a lifetime devoted to the study of yellowjackets and hornets, I can’t resist examining one of the most outlandish of the bunch: simulated wasp nests that purport to serve as protection against real ones.

Fraudulent fakes.

I’m familiar with two examples of these curious articles, both manufactured in China (Figure 1, above). The older product is essentially a collapsible paper Asian lantern with an open bottom and an ovoid shape that indeed looks superficially like some Dolichovespula nests — at least in cartoons. It is pleasingly proportioned, quite appealing, and for years I’ve had one hanging from the suspended ceiling grid over my office cubicle, clearly marking from across the room where the entomologist sits. Dozens are strung from overhead lines in my fantasies of an elegant, entomologically themed garden party.

The second is a sturdy polypropylene bag that has no esthetically redeeming features whatsoever and looks vaguely like a big, misshapen chrysalis outfitted in urban camo. They are joined in the photographic lineup by two examples of the real thing, both mature nests of D. maculata, an atypically large black and white yellowjacket that shares several behavioral similarities with Vespa spp. and has long been granted the official common name (by the Entomological Society of America) of “baldfaced hornet.” The specimens were selected to illustrate how different in appearance the nests of this species can be, which is influenced by a wide range of local environmental factors.

The claims of both products are similar. The first advises the purchaser to hang the fake nest “in an area that is frequented by wasps, yellowjackets or hornets and the territorial insects will detect an existing nest and flee to another area. Wasps are very territorial and will not usually build their nests within 200 feet of another nest.” The second states that the bag “acts like a scarecrow for wasps — other wasps see it as an enemy nest and avoid the area. No harmful chemicals, no dead wasps to clean up, no maintenance and no more wasps!”

Neither of these items costs very much money, but I refuse to believe that even the most naive citizen would purchase them without harboring some doubts that the natural world could be so easily kept at bay. Nevertheless, although they may be inconsequential in the greater scheme of things, another part of me sees the sale of such nonsensical junk as a sad reminder of our society’s seemingly bottomless ignorance about the natural world, not to mention the inevitable aspersions they cast on the legitimate field of biorational pest control. So for what it’s worth, these are the reasons why scarecrow wasp nests do not even have a shred of validity:

1.) The central premise of these products is that social wasp colonies are “territorial.” A territory simply means any defended area, but the concept takes several different forms. With animals, the most common use of the term is when a male defends a space against other males of his species (or, as amply demonstrated by carpenter bees, what he thinks are other males of his species) to maximize reproductive success. However, in the context of scarecrow nests, the word refers to a space defended by one or a group of animals against others of the same or closely related species, to maximize access to multiple resources (e.g., food, nesting sites, etc.). This definition can be expanded to include defense against any species that is deemed to pose a threat.

Yellowjacket and hornet colonies are famous for the latter, particularly if the intruder is large, darkly colored and produces strong vibrations that affect the nest. But other than defense of the immediate nest area against potential predators (mostly vertebrates, although some true hornets may raid the nests of smaller wasp species), the only territoriality that has been documented in these wasps involves competition for nest sites by foundress queens in the spring, and pertains to either the cavity in which a subterranean or structural nest is located, or the tiny embryo nest itself (Figure 2, right). Once workers have emerged and foundresses stop foraging, individuals from different colonies appear to totally ignore each other, as well as each other’s nests. In other words, workers do not, to any degree, exhibit the type of territoriality claimed by the marketers of both brands of scarecrow nests. (In fact, the phenomenon of “colony drift,” normally associated with honey bees, has also been reported in yellowjackets, in which workers from one colony will be allowed by guard wasps to enter another nest of the same species.)

2.) A second issue is the assertion by one of the products that foundress queens in the spring are constrained by what amounts to a 400-foot wide territory for nest establishment. It is difficult to fathom how a queen could possibly even know about the existence of most other embryo nests within that relatively enormous and complex space, let alone their precise location. Be that as it may, it is not at all uncommon to find multiple, healthy colonies located quite close to one another in favorable nesting habitat (Figure 3, right), perhaps due to the mechanism of “social facilitation” among searching foundresses. I have combed the yellowjacket and hornet literature in vain for some biological origin of that 200-foot radius figure on the fake nest’s packaging and other advertising. Could it be that it was chosen by a clever marketer because it is so often the key parameter in various types of human legal exclusion zones? Across a multitude of jurisdictions, 200 feet is the magic number for civil protective orders, alcoholic beverage license control (in proximity to schools, churches, etc.), following behind a fire truck, mandatory brush clearing around structures in potential wildfire areas, slow-no-wake zones for boats near shorelines and so forth. Why wouldn’t wasps adopt the same standard?

3.) A third inconsistency is that the scarecrows are intended to be hung from a branch or a structure in order to mimic a typical Dolichovespula nest. But foragers in this genus prey almost exclusively on live arthropods and thus are not at all the type of yellowjackets that earn their pest status by extensively scavenging on human food (Figure 4, right). If the object of these products is to decrease the number of annoying freeloaders that take all the fun out of eating outdoors, they’re targeting the wrong species of wasps. In fact, out of 20 yellowjacket/hornet species in North America, only six (all in the genus Vespula, and all of which nest in protected cavities, normally underground) typically feed on dead meat or processed human food.

4.) Finally, a scarecrow hornet nest would seem to suffer from the same intrinsic drawback as any other type of scarecrow. Is it reasonable to expect an animal equipped with such a sophisticated array of visual and, especially, chemical sensors as a social wasp to mistake these coarse approximations for the genuine article?
 

The Truth is in the Details.

I’ve devoted considerable space to debunking such an obvious travesty to point out the type of arcane biological details that may be trivial in some circumstances but are essential to consider when developing any valid pest management device. It’s a perfect demonstration of how applied research programs by legitimate firms must exhaustively mine the basic scientific literature for obscure facts that may make or break the practical utility of a promising new concept. One wonders whether the inventors of the sham nests actually believed they had created a technically solid contrivance that could deliver real consumer value, or whether they were primarily fixated on potential profits from the gullible. Not surprisingly, the patent (as a “wasp repellent device”) of one of the products — the other is apparently unpatented — is almost exclusively devoted to its design and offers no supporting evidence for its premise. It does make note of a few of the Internet discussions over the years that have advocated the practice of hanging stuffed paper bags outside as a home remedy to deter social wasps. One thing is certain — no hymenopterist was ever consulted (or at least heeded) in the making of these fakes.

This article has been excerpted from a forthcoming book by the author on the theory, history and practice of IPM in buildings. The opinions expressed herein are the views of the author and do not necessarily reflect the official policy or position of the U. S. General Services Administration (GSA). Dr. Greene is entomologist and National IPM Coordinator for the GSA’s Public Building Service in Washington, D.C. He can be reached via email at agreene@giemedia.com.