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

Managing Slugs in Crop Fields and Gardens

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Slugs are a common field crop and horticultural pest. Managing them is challenging because their damage is often confused with other pest damage, and pesticide options are few and expensive. Luckily, knowing what to look for and the growing practices that reduce slug damage helps reduce the problems with this pest.

What exactly are slugs?

Unlike most other plant-feeding pests found in fields or your garden, slugs are not insects. Instead, they are soft-bodied, legless mollusks that are covered in slimy mucus that they secrete and leave behind as a trail. Slugs dry out easily, so they prefer environments with lots of shade and moisture. Slugs feed on a wide variety of food sources, but when they eat plants they can cause a significant amount of damage making them the bane of many farmers and gardeners.

In our area, the most common slugs found in crop fields and gardens are:

  • Gray garden slugs – about 2 inches long when fully grown. Ranging from cream-colored with irregular gray spots to dark brown with dark spots.
  • Marsh slugs – Smaller, about 1 inch long. Tend to be dark.

Eggs of both species are small, clear, round, and gelatinous. They are usually laid in clusters under plant residues.

Images of two types of slugs: gray garden slug, marsh slug, slug eggs
A) A gray garden slug, B) two marsh slugs, and C) slug eggs under old soybean roots
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From moth to monster: Hornworms return

A few weeks ago you were sitting back admiring your freshly planted garden. Neat little rows of tomato, pepper, squash, and cucumber plants accompanied by flowers and herbs were all planted in view from your back deck. As you sat there basking in the evening sun, relishing in your hard work, a little moth fluttered from flower to flower sipping nectar.

hornworm moth
A hawkmoth, the Carolina Sphinx, is the adult form of a tobacco hornworm. Photo: Mike Raupp, University of Maryland, Department of Entomology

With her hummingbird like flutters, a Carolina Sphinx Moth floated through your garden, unassumingly laying her eggs on your newly planted tomato and pepper plants. Within a few days, from her little green eggs emerged a tiny but very hungry green caterpillar.

hornworms
Hornworm caterpillars. Photo: Rachel Rhodes, University of Maryland Extension

Since that day, the ravenous little green hornworm caterpillar has spent his days munching away, perfectly hidden by the copious green foliage of your tomato plants, growing bigger and bigger. You begin to notice stems of complete defoliation. Maybe you think it’s a bunny or deer having a nighttime nibble as the little green caterpillar stays camouflaged, until the moment you notice the red-tipped horn and the very large green body of a caterpillar measuring almost 4” in length hanging on your prize winning tomato plant. Continue reading

Are Stink Bugs Bugging You? Are Wasps the Solution?

project stink-be-gone logoSummary: Learn how University of Maryland researchers and University of Maryland Extension (UME) Master Gardeners collaborate on research to reduce brown marmorated stink bug populations in Maryland. Project Stink-be-Gone, by Rebeccah Waterworth

As temperatures cool, many of you probably have had to share your homes with bugs. One of the most notorious of these squatters is brown marmorated stink bug (BMSB) (Fig. 1). It is also a serious pest of many economically important crops. Paula Shrewsbury and I are interested in developing sustainable pest management practices for BMSB, particularly biological control using small wasps (Fig. 2). These critters are also known as parasitoids, and they lay their own eggs inside a stink bug egg. The baby wasp (larva) inside the stink bug egg eats the developing stink bug. After about 10 days, the wasp larvae have become adults, chew their way out of the bug eggs, and fly off to look for new bug eggs to parasitize! Stink bugs do not hatch from the eggs where wasps emerged (see the video at the end of this post).

brown marmorated stinkbug adult
Fig. 1  An adult brown marmorated stink bug, Halyomorpha halys. Photo by David R. Lance, USDA APHIS PPQ from bugwood.org.

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