Insects: Our Most Under-Appreciated Neighbors

Why should I want bugs, insects, and creepy crawlies in my yard or green space?

Insects are an incredibly diverse group of organisms, with 91,000 described species in the United States and likely an equal number yet to be described by scientists. Only an exceedingly small fraction of these species ever have negative impacts on humans as “pests” (<1% of species). Often the overabundance of pest species is due to human agricultural and landscape practice choices. The vast majority of insects in shared spaces with humans like yards and parks are going about their own lives. In addition to being fascinating creatures deserving of habitat in their own right, they also often contribute to unnoticed but very important tasks that help humans, termed “ecosystem services.” The next time you see one of these critters in your yard, consider thanking them rather than smashing them.

What are ecosystem services?

Ecosystem services are benefits that humans gain from the environment. Examples of ecosystem services include water filtration, raw material production, erosion control, and pollination. Some ecosystem services, like the maintenance of atmospheric gasses (e.g. plants remove carbon dioxide and produce oxygen that humans breathe), are noticeable and directly impact our everyday lives. On the other hand, services like decomposition may go unnoticed because they indirectly affect us.  

Insects (and their arthropod relatives like spiders and earthworms) play vital roles in many ecosystem services. This is often due to insects interacting with plants in some way, though insects also provide food for many other animals. Below are some examples of the ecosystem services that insects contribute to.

Water filtration

Filter-feeding insects positively affect water quality because they remove particles of dead organic material. Insects retain many of the nutrients they filter out of the water, thus reducing the likelihood of algal blooms, their associated toxins, and dissolved oxygen “dead zones.” This is crucial because clean water provides habitat for other plants and animals like fish and amphibians. It also means less effort is required to purify water for human use. 

Types of insects that improve water quality:

  • Blackflies, mayflies, stoneflies, and caddisflies (Note: the underlined insect groups are not “true” flies in the taxonomic Order Diptera; they are part of other orders.) 

Other types of organisms that improve water quality:

  • Mussels, crayfish, snails

More information: Why Care About Aquatic Insects

Biocontrol

Biocontrol is when natural enemies are used to suppress pests and reduce the amount of damage they cause. Natural enemies are insects that are antagonistic to pest insects. There are three types of natural enemies: predators, parasitoids, and pathogens. Preserving natural enemy populations is crucial to reducing our reliance on pesticides because when natural enemies are active, pest outbreaks are less likely to occur in the first place. Predators need food all year, so they also need alternate prey available in order to prevent pest outbreaks. Pesticides eliminate beneficial insects in addition to pests, so they should be used only as a last resort.

Fun fact: Fireflies spend much of the year as larval predators belowground, feeding on pests like grubs in turfgrass yards. If no prey is available in yards, then there will be no display of adult fireflies in the summer.

Types of insects used for biocontrol:

Other types of organisms used for biocontrol:

  • Fungi, birds, amphibians, reptiles, and mammals

More information: Approaches to the Biological Control of Insect Pests.

Seed dispersal

Seed dispersal is when seeds are moved away from the parent plant. Seeds are moved when insects knock them off while feeding or when insects collect and then move seeds to a new location. Seed dispersal is important because it reduces resource competition between the parent plant and offspring plants. It also makes germination and seedling survival more likely, especially in arid climates. 

Types of insect seed dispersers:

  • Ants (most effective), beetles, wasps, thrips, and some moths

Other types of seed dispersers:

  • Fruit-eating animals (frugivores), such as some monkeys, lizards, and bats
  • Unwitting animal dispersers of sticky seeds like this

More information:

Seed Dispersal – The Australian Museum

The Conservation Physiology of Seed Dispersal

Decomposition & nutrient cycling

Nutrient cycling and decomposition are two important processes that rely on one another. Nutrient cycling is when soil nutrients are taken up by plants, insects eat plants, and then those nutrients are reintroduced into the soil when dead insects and droppings are broken back down into nutrients via decomposition. Decomposer insects help clear dead animals and plants off the ground which would otherwise accumulate everywhere. They also help create soil texture and circulate nutrients back into the soil, which plant populations and productivity depend on.

Types of insect decomposers:

  • Many beetles, springtails, termites, wood cockroaches, and some fly larvae (maggots)

Other types of decomposers:

More information: Decomposers

Supporting food webs

Insects are a main source of protein and nutrition for many animals (and even some plants). They play a crucial role in transferring energy from plants to larger animals that eat insects like spiders, birds, frogs, fish, bats, foxes, opossums, and bears. This wide food base that they provide allows for functioning, stable ecosystems that are resilient to disruptions.

Fun fact: By weight, there are roughly 300 times more insects than humans on Earth.
There are so many animals that eat insects, but here are just a few examples:

  • Terrestrial bird species, in particular, feed their babies almost exclusively with insects, and if there are fewer insects, baby birds are less successful at fledging from nests.
  • Popular fish like salmon, bass, and trout eat insects, especially when they’re young.
  • Grizzly bears will eat tens of thousands of moths a day to prepare for hibernation.

Pollination

Pollination is the transfer of pollen between flowers, resulting in flower fertilization and seed/fruit production. It is an unintentional consequence of pollinators going from flower to flower to feed themselves. Pollination is crucial for human survival, as 80% of plant-based foods and products rely on animal pollination. According to the USDA, pollinated crops are worth $18 billion in the US alone. Foods requiring pollination include apples, blueberries, chocolate, coffee, grapefruit, peaches, peppermint, sugarcane, tequila, and vanilla. 

Fun fact: beetles were likely the first insect pollinators– starting 200 million years ago!
Types of insect pollinators:

  • Bees, wasps, beetles, flies, ants, butterflies, and moths

Other types of pollinators:

  • Birds and bats

More information:

Pollination Basics

What is Pollination?

Why is Pollination Important?

Pollinated Foods

By Yasmine Helbling, Kelsey McGurrin, and Karin Twardosz Burghardt, from the University of Maryland Department of Entomology, Burghardt Lab

Biological pest control: parasitoids

¿Hablas español? Aquí esta una traducción: Control biológico de plagas: los parasitoides

Parasitoids are natural enemies of pests that, like predators (ladybugs and flower flies) can help us keep pest populations at bay or eliminate them from our gardens.

Parasitoid or parasite? Let’s learn the difference between these terms

Before saying more about this group of natural enemies, let me tell you that it is very common to confuse the term “parasitoid” with the term “parasite.” Parasites and parasitoids have in common the need for a host for their development. The difference between the two types of organisms is that parasitoids kill their host to complete their life cycle. That is, the parasite can live at the expense of the host without having to kill it, while the parasitoid ends up killing its host upon completion of its life cycle. Parasites are generally known to be annoying and even transmit diseases to animals, plants, and humans, while parasitoids are beneficial insects, as they help us control pests.

What is a parasitoid?

Parasitoids are insects that insert their eggs into the body or egg of another insect (host) in order to complete their life cycle. Parasitoids go through complete metamorphosis, four different stages of development: egg, larva, pupa, and adult. To finish their development, the parasitoids must feed on their host, and the females first deposit their eggs in their host. As soon as the parasitoid egg hatches, the larvae begin to devour the tissues of their host. Once the larvae reach a certain size, they become pupae, after which the adult emerges, killing the host.

Parasitoids can be classified according to their oviposition (egg-laying) behavior. Endoparasitoids are the parasitoids that lay their eggs inside the body or egg of their host. In contrast, ectoparasitoids oviposit on top of the body of their host, that is, on the surface of their body. To see these fascinating creatures in action you can, watch a video of endoparasitoids and one of ectoparasitoid activity.

Life cycle of an ectoparasitoid (adapted from Presa-Barra et al 2020)

life cycle steps of an ectoparasitoid

Life cycle of an endoparasitoid (adapted from Presa-Barra et al 2020)

life cycle steps of an endoparasitoid
Continue reading

Hidden Garden Party: Who’s Eating Whom?

aphids on cantelope leaf
Heavy aphid infestation on the underside of a cantaloupe leaf. Photo: Ashley Bodkins

Who loves a party? I know I do, especially a summer BBQ with all the family favorites! Insects are no exception and really know how to have some fun. Pictured above is a party of aphids, which are tiny little suckers — literally. They are soft bodied insects that suck plant sap with their piercing, sucking mouthparts.

aphid damage leaf curling
Twisted, deformed leaves are a symptom of aphid feeding damage. Photo: Ashley Bodkins

Aphids can come in many colors ranging from shades of green to black. They suck juice right from plant tissues, resulting in bent and twisted leaves as seen in the picture above. Aphids are generally only found on the underside of leaves and can be in very large numbers. Once a colony is established females can even reproduce without a male.

They secrete a sweet, sugary waste liquid that is called “honeydew”. Sometimes a fungus grows on the
honeydew, which is called sooty mold and looks like someone smeared coal soot on the plant.

Seeing ants on your plants can be your first sign that there is an aphid infestation. Ants love honeydew and often “farm” aphid colonies to reap the benefits.

ladybird beetle
The ladybird beetle is a natural enemy of aphids. Photo: Ashley Bodkins

Aphids can transmit plant virus diseases, but generally they aren’t found in large enough numbers to warrant a chemical control. Mother Nature actually Ahas some really interesting predators for aphids. In fact, the beautiful red with black spotted ladybird beetle (ladybug) is an avid aphid hunter and can eat more than 5,000 aphids throughout its four-part life cycle.

lady beetle larva eating an aphid
Ladybird beetle larva eating an aphid. Photo: Lenny Wells, University of Georgia, Bugwood.org

Other natural predators include lacewings, flower fly larvae, and parasitic wasps. Evidence of natural predators include “aphid mummies” which are light brown, hollow aphid bodies that were once inhabited by parasitic wasp larvae.

aphid mummies
Mummies of oleander aphids parasitized by Aphidius sp. wasp. Note the hole in the aphid at the top right of the photo indicating a wasp has emerged. Photo: David Cappaert, Bugwood.org

syrphid larva
Flower fly larva feeding on an oleander aphid. Photo: David Cappaert, Bugwood.org

Physical control of aphids can be accomplished by spraying the pests with a strong stream of water. This causes them to fall off the plant and hopefully disrupt their feeding. As a last resort, use chemical
controls such as insecticidal soap or Pyrethrum products.

By Ashley Bodkins, Senior Agent Associate and Master Gardener Coordinator, Garrett County, Maryland, edited by Christa Carignan, Coordinator, Home & Garden Information Center, University of Maryland Extension. See more posts by Ashley and Christa.