Category Archives: Insects and ecosystem services

Do people dislike insects? Why?

Most insect scientists (and I’d guess, most people in general) express a general sense that there are lots of people that don’t like insects. We probably could all come up with anecdotal evidence of this. For instance, my mother-in-law talks about trouble eating in our apartment because I have a poster of grasshopper in our kitchen, and this makes her queasy. I’d guess, however, that most people just ignore them. Angela talks gave me some anecdotal evidence of this: She always helps out with an exercise at the Konza prairie to get kids collecting insects, i.e. the insect grab at the Konza Visitor’s Day. After collecting insects, the kids have a booklet to fill out that asks them to give the scientific name of an animal. Even though they are looking right at a terrarium full of insects they all try to think of a mammal to list. Also as qualitative evidence, I can find lots of blogs / blog posts (like this or this or this) and newspaper articles (like this or this or this) that express the perception that insects are often disliked. But, I had only read one or two studies that actually tried to quantify this.

For this post, I wanted to delve deeper into these questions: has it been shown lots of people generally dislike insects? And, if so, why do people dislike insects? Does this differ among social groups, ages, or genders? Does this differ culturally? 

Avoidance, ignorance, and dislike of insects

The reason that I hadn’t read a lot of studies about how people perceive insects is that there aren’t all that many out there (although, admittedly, my search has been rather limited thus far). The studies that I have found that actually take some measurement of how people feel about insects (especially relative to other groups of animals) do tend to generally find what we all expected: both adults and children generally negative attitudes towards or ignorance / avoidance of insects. I was a little dismayed that all studies that measured a gender difference reported that negative attitudes towards insects (or more generally invertebrates) seem to be stronger in females than males. There have been conflicting findings about age, however, some report people dislike insects less as they get older, and others the opposite trend. I could not find any studies outside of the US and Europe, so this discussion is unfortunately represents Western attitudes, only. (Also, if anyone is aware of studies from non-US or European places, we’d love to know about them. I suspect Asian attitudes towards insects could be different, as insects can be culturally important in some Asian cultures, as we discuss here.)

Here are some examples:

  •  US adult aversion to insects: A survey by Kellert (1993) showed that of 214 residents of a small town in Connecticut, members of the public and farmers generally viewed invertebrates (insects and spiders in particular) “with aversion, anxiety, fear, avoidance, and ignorance”, while scientists and conservation organization members were more positive and knowledgeable of them In accordance, most of the general public disapproved of major expenditures to protect threatened invertebrate species. Most people seemed to better understand the roles of lepidopterans in relation to agriculture and gardening, but didn’t know the taxonomy or general importance of other groups. Positive attitudes towards invertebrates were greater in males than females, those with above a high school education, and in younger respondents compared to older.
  • Norwegian adult aversion to insects: Bjerke and Østdahl (2004) showed that in one Norwegian city, the majority of people dislike most invertebrate species, as compared to mammals and birds, which were generally liked by most people.  Butterfly species were liked, and grasshoppers were considered neutral species. Men were the ones that were most likely to prefer the disliked species, like insects, and, for some invertebrate species, there was a tendency for invertebrates in general to be more well-liked by older people.
  • Children’s general ignorance of insects: Children tended to underappreciate the importance of insects and their diversity to different ecosystems, and ultimately, humans. Drawing on children from Nebraska and New Jersey, Strommen (1995) found that children had very little awareness of insects as members of forest ecosystems (only 13 % of them included them in drawings to depict forest systems) As an aside, boys had more knowledge about forest life than girls. Barrow (2002) found that most students (K-6) interviewed had more knowledge about the harmful effects of insects than their helpful effects.  Snaddon, Turner and Foster (2008) showed that children visiting the University Museum of Zoology in Cambridge vastly underrepresented insects as a component of rainforest biodiversity in drawings to depict the biodiversity in a rainforest, and then analyzing these drawings.  Previous work by Snaddon and Turner(2007) in the UK has shown that children know more about groups of insects represented in popular culture, and that their knowledge was not necessarily about insect groups that were most common or threatened in the UK.

Why do we dislike and  / or ignore insects?

I found very little evidence of this, largely just speculation in discussions of the papers above (and other). As such, I’ll put forth what I’ve always the two things that I’ve always thought contribute most, which is partially in line with what the above authors have said, and in line a couple of points from Hillman’s “Why we hate bugs”.

First, because we are more closely related to mammals, we can understand them better and appreciate the “beauty” they possess more easily. I think that many people are just very confused by insects. They look very different than us. They have different life cycles, reproduce differently, and behave in very different ways than us. Confusion and misunderstanding of insects often leads to aversion and fear.

Second, a handful of insects that can potentially harm people or resources they depend upon have given the rest a bad wrap (I can think of other animal groups that this has happened to, such as snakes and sharks). This phenomenon may be more prominent for insects, however, because nearly everyone has firsthand knowledge of the potentially harmful (at the very least irritating) effects of insects via insect bites, and we all hear news of insect outbreaks harming agriculture or disease outbreaks spread by insects. We fear and avoid that which may do us harm, and since most people know very little about insects, they fear and / or avoid insects in general.

So…what can change these negative perceptions?

There are certainly many on social media that are aiming to change this general dislike. For instance, an insect natural history class at Berkeley actually reviewed bug blogs, and certainly a main goal of many of these is to get people to appreciate the insect world more. There are lots of admirable people and organizations that actively seek out opportunities to educate the public about insects and their roles in ecosystems. For instance,The Bug Chicks have a wonderful blog, do events and media all to teach the public about insects and arthropods. And, with regards to children’s perceptions of insects, Chris Buddle has posted about how well-received (and fun!) his outreach with kids about bugs has been.

With the growing awareness that insects are very important to humans, including the recent UN recognition of their potential as an important food source, human perceptions must change at some point. Other than those of us that actively seek out local opportunities to change human perceptions about insects, is there a way to do this at a larger scale? If I am right about why people dislike insects, this change in perception would mean: 1) fostering a better understanding of insects to dispel fear and avoidance, and 2) showing that most insects are beneficial, and educating people about those that are potential harmful. I’m guessing one cornerstone of this would be to start with kids, as many public awareness programs do.

We’d love to hear any ideas that are floating around out there about both why people dislike and fear insects, and what can be done to change this widespread perception.

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Unsung Heroes: The Humble Dung Beetle

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A dung beetle from Konza Prairie Biological Station in KS, USA

If I asked someone to make a list of beneficial insects, he or she would most likely think of pollinators like honeybees or maybe predators such as dragonflies.  I suspect that very few people would think to include dung beetles on their list, but these insects are actually very important, ecologically and economically.  Chelse and I were recently at a grassland ecology conference held at the Konza Prairie Biological Station.  We had a very lively and very entertaining discussion with an ecologist from South Africa about whether or not insects were important to ecosystems.  This ecologist maintained that insects could not have strong effects on ecosystems the way that large vertebrates do, however he did make a single exception: dung beetles.  So why are dung beetles so important?  What do they do and why should we care?

Let’s start with some natural history.  There are around 7,000 known species of dung beetles, which belong to the superfamily Scarabaeoidea.  Dung beetles are found on all continents except Antarctica, and occur in a variety of habitat types including grasslands and forests.  Dung beetles are coprophagic, which means they eat poop.  Dung beetles eat poop as adults and as larvae.  Many dung beetles roll the dung into a ball that is used for food or to create a “brooding ball”, in which the females lay eggs.  After the eggs hatch, the larvae feed on the dung.  Dung beetles can be grouped into three main categories.  “Tunnelers” bury their brooding balls in the ground, often near the original dung.  “Rollers” transport the dung balls farther away from the original dung, often in remarkably straight lines, before they bury it.  Dung beetles recently made news when it was discovered that they can use the stars to orient themselves!  Dung beetles are the only species apart from humans known to do this.  “Dwellers” brood their young inside the dung, rather than in separate brooding balls.

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Watching dung beetles is fun! I’m always impressed by how fast they move and how symmetrically round they get the dung balls. This beetle is from Konza Prairie, where there is a herd of ~ 300 bison.

Most areas support a diverse community of dung beetles made up of species from each of these groups.  The effects of dung beetles on ecosystem services depend on the composition of the dung beetle community.  Dung beetles with different behaviors (i.e. rollers vs. dwellers) will have different effects on ecosystem services.   The maintenance of ecosystem services by dung beetles depends on a diverse assemblage of dung beetle species.

So how do dung beetles affect ecosystems?  Dung beetles contribute to several ecosystem services.   A nice review paper by Nichols et al (2008) details the many ecosystem services provided by dung beetles.  I’ve summarized the highlights from their paper here.

Dung beetles are important to nutrient cycling.  Poop contains many nutrients.  By breaking poop into smaller pieces and moving it underground, dung beetles facilitate decomposition and make the nutrients available to other organisms.  Studies have found that many soil nutrients are increased when dung beetles are present.  Dung beetles also increase nitrogen mineralization.  Nitrogen mineralization is the process by which nitrogen is converted from an organic to an inorganic form, making it available for use by plants (and subsequently, the rest of the food web).  This is important because nitrogen is often a limiting nutrient in terrestrial systems, which means that adding nitrogen can increase productivity.  That’s why fertilizers contain nitrogen.

Dung beetles are also important for soil bioturbation.  Bioturbation is the mixing and redistribution of sediments.  This is an important process that affects soil moisture and soil aeration.  For comparison, earthworms are also important for bioturbation, which is why gardeners like to see them in their flowerbeds.  Tunnelers are especially important for bioturbation.

By increasing nitrogen availability and by facilitating decomposition, nutrient cycling, and bioturbation, dung beetles can increase plant productivity.   Many studies have found that dung beetles can increase plant biomass, nitrogen content, and grain production.  Some studies have even shown that the positive effects of beetles on plant production are equal to or higher than the effects of chemical fertilizers!   Dung beetles may also contribute to plant productivity by dispersal of seeds found in dung, which can lead to increased plant recruitment.   And some species of dung beetles are important pollinators of decay-scented flowers. 

Dung beetles can reduce the abundance of parasites and flies that breed in dung.  For example, fly abundances and parasite loads in livestock decrease when dung beetle abundance is experimentally increased.

The importance of dung beetles to livestock production has been demonstrated in Austraila, where cattle were introduced by Europeans.  Because the local dung beetles were not acclimated to feeding on cattle dung, rangelands became fouled with slowly decomposing cattle dung.  Cattle will not forage near dung, so as the amount cow poop increased, rangeland available for cattle foraging declined.  Pests like flies also increased in abundance, but declined sharply after dung beetles were introduced.

Economic importance.  Losey and Vaughan (2006) published a really cool paper that estimates the economic value of four ecosystem services (dung burial, pollination, pest control, and wildlife nutrition) provided by insects.  They estimated the economic benefit of dung beetles to cattle production in the United States is worth at least $380 million a year!  This is based on the many ecosystem services that dung beetles provide that increase forage production and decrease livestock pests.  It’s important to note that this figure doesn’t include the effects of dung beetle on production of other types of livestock, or on ecosystem services not related to livestock production.  This means that the economic value of the ecosystem services provided by dung beetles in the United States is actually much higher.

Bison at Konza Prairie.  A health dung beetle community contributes to sustainable management of bison and other large herbivore populations.

Bison at Konza Prairie.  A healthy dung beetle community contributes to sustainable management of  ecosystems like grasslands and the animals that live there.

Importance of a diverse dung beetle community.  Dung beetles are important to ecosystems and provide a variety of important ecosystem services. There is still a lot to learn about how dung beetles affect ecosystem processes, especially in forests.  But protecting dung beetle diversity and abundance may be critical to the sustainable management of many ecosystems, including rangelands used for livestock production.  For example, a recent study by Beynon et al (2012) finds that high dung beetle species richness increases dung decomposition rates, and may be especially critical for maintaining ecosystem services when the system is disturbed.  They measured decomposition rates of cattle dung exposed to one, two, or three species of dung beetles.   After 36 weeks, more dung was decomposed when three species of dung beetles were present, than when only one or two species of dung beetles were present.  They also conducted the experiment on dung collected from cattle treated with ivermectin, which is used to reduce parasites.  Dung decomposition in these treatments was lower than dung decomposition of control treatments (no ivermectin), but not when three dung beetle species were used.

So what do these data tell us?  They tell us that ivermectin treatment of cattle can have negative effects on decomposition by dung beetles.  However, when a more diverse assemblage of dung beetles (3 species) was present, this negative effect of ivermectin disappeared.  This is because each of the dung beetle species used responded differently to the ivermectin treatment.   So, having several species available means it is more likely that there is at least one species that can tolerate new or different conditions.  Maintaining high species diversity of dung beetles may be critical to maintaining the ecosystem services they provide.

So give some love to the humble dung beetles!  Not only are they really cool animals, they provide many important ecosystem services that are economically and ecologically valuable.

References:

Beynon, S. A., D. J. Mann, E. M. Slade, and O. T. Lewis. (2012). Species-rich dung beetle communities buffer ecosystem services in perturbed agro-ecosystems. Journal of Applied Ecology 49:1365-1372.

Losey, J. E. and M. Vaughan. (2006). The economic value of ecological services provided by insects. BioScience 56:311-323.

Nichols, E., S. Spector, J. Louzada, T. Larsen, S. Amequita, M. E. Favila, and The Scarabaeinae Research Network. (2008). Ecological functions and ecosystem services provided by Scarabaeinae dung beetles. Biological Conservation 141:1461-1474.