Native trees for insects: the beetles, wasps, cicadas and fireflies that everything else eats

Almost everything people plant a tree to attract eats insects first. The National Wildlife Federation puts it at 96 percent of terrestrial birds relying on insects, and a pair of chickadees needs more than 6,000 caterpillars to raise one brood. The insects are picky in turn: most leaf eaters can only eat the plant lineages they evolved with, so a yard of Asian and European ornamentals has a hole at the bottom of its food web. Caterpillars and bees each have an article of their own; the subject here is the rest of the crowd, from sawflies and gall wasps to fireflies and cicadas, and what it takes to keep them.

Insects feed everything else

Insects are the link between leaves and nearly everything with a backbone. In a four-year study of Carolina chickadees in yards around Washington, DC, caterpillars and spiders grew scarcer as yards filled with non-native plants; the birds switched to poorer prey and raised fewer young or skipped breeding, and the population held its own only where non-native plants were under 30 percent of the plant biomass. What birds do with all this is in the birds article.

The insects themselves are thinning. Malaise traps run in 63 German nature reserves from 1989 to 2016 recorded a 76 percent fall in flying insect biomass, and 82 percent in midsummer. A 2021 review of the studies that exist found reported declines commonly running 1 to 2 percent a year, from land turned to farms, lawns and pavement, insecticides, introduced species, a warming climate and light at night. A landowner controls more of those causes on an acre than any agency does.

Why a native tree and not just any tree

Plant-eating insects are specialists. A survey of more than 7,500 herbivorous insect species at 17 sites from Canada to Brazil and from Britain to New Guinea found that on average 69 percent of caterpillar species feed on a single plant family (about 60 percent outside the tropics), with the true generalists a thin tail. The limit is leaf chemistry, and a tree from another continent carries chemistry nothing here has met. Across the country, native oaks host more than 500 species of caterpillars; ginkgo hosts 5.

Across the counties Douglas Tallamy’s team sampled, about 14 percent of native plant genera support more than 90 percent of the butterfly and moth species, with oaks first, then willows, cherries, pines and poplars. The other guilds follow the pattern and most are narrower still. A gall wasp makes its gall on one group of oaks and nothing else. The cone gall aphid of witch hazel (Hamamelis virginiana) lives on witch hazel; the spiny witch hazel gall aphid needs witch hazel and a birch in alternate generations to complete a life cycle at all.

In a University of Delaware trial of native woody plants against their cultivars, most bred traits made no consistent difference to how much leaf-eating insects ate; leaves bred to come out red, blue or purple were avoided. A purple-leaved ninebark (Physocarpus opulifolius) is a ninebark the ninebark leaf beetle avoids. Seed-grown, green-leaved species are the safe choice, and every plant we sell is one.

Leaf chewers: sawflies, beetles, katydids and walkingsticks

The Forest Service’s account of white oak reads like a census: leaves eaten by orange-striped oakworms, variable oakleaf caterpillars, oak leaf tiers and walkingsticks; wood by the two-lined chestnut borer and the oak timberworm; sap by golden oak scale; acorns by two genera of weevils, the filbertworm and cynipid wasps that gall the acorn itself. And that is only the insects foresters worry about.

Caterpillars are the largest group of leaf chewers, not the only one. Sawflies are wasps whose larvae look like caterpillars and feed in groups; the dogwood sawfly feeds on silky dogwood (Cornus amomum) from July, then leaves to winter in soft, decaying wood. The common true katydid lives in the canopy, eats tree leaves, sings from July into November and leaves its eggs on bark for the winter. The northern walkingstick eats oak leaves and in a bad year strips scarlet oaks in the northern part of their range. None needs control on a healthy tree. They are what the tree is for.

Sap feeders, from aphids to periodical cicadas

Aphids, scale insects, leafhoppers and treehoppers drink sap and pass the surplus out as honeydew, the sugary waste that everything from harvester butterflies to stag beetles feeds on. The colonies feed the predators below and many songbirds. The oak treehopper guards her nymphs on an oak twig, bumping predators away. The harvester, the only North American butterfly with carnivorous caterpillars, lays its eggs beside colonies of woolly aphids for its young to eat, and the adults drink the honeydew.

Periodical cicadas are sap feeders too. The nymphs spend 13 or 17 years 2 to 24 inches underground drinking sap from tree roots, then come up by the hundreds of thousands to the acre (as many as a million), and birds gorge on them. Each female lays 400 to 600 eggs in pockets cut into twigs, preferring oaks, maples and apples; the twig beyond the cut dies and hangs brown. A mature tree loses twig tips and nothing else. A newly planted tree can be badly cut, so in a brood year net anything under 10 feet with half-inch mesh; insecticides do nothing measurable to the numbers. In Maryland, Brood X emerged in 2021 and returns in 2038; Brood XIV came up in 2025.

Gall makers

A gall is plant tissue grown to an insect’s instructions, and oaks are the world center of it: more than 700 of the roughly 1,000 known oak gall wasp species live in North America. When researchers reared insects from more than half a million galls collected off 32 North American oaks, 155 gall types yielded 151,075 arthropods: inquilines that move in beside the gall maker, parasitoids that hunt it and hyperparasitoids that hunt the hunters, as many as 15 to 25 species to a single gall type. The galls article covers what they look like and why they need nothing from you.

Oaks are not alone. Hackberry (Celtis occidentalis) carries at least ten species of Pachypsylla psyllids that make its nipple and blister galls and winter as adults in its bark. Witch hazel has its cone gall aphid on the leaves and its spiny gall aphid at the flower buds. None harms the plant in any way that matters, and each is a meal for something with a beak.

Miners and borers, and the borer that is different

Miners live inside a leaf. The native holly leafminer is a small fly that lays its eggs only in American holly (Ilex opaca); the larvae tunnel the leaf all winter, and a braconid wasp kills 3 to 58 percent of them on any one tree. Most native borers work on dead or weakened wood; the two-lined chestnut borer takes oaks after drought, fire, frost or defoliation. The locust borer, a longhorn striped like a yellowjacket, lays its eggs in the bark of black locust (Robinia pseudoacacia) and no other tree; the adults emerge in late summer to feed on goldenrod pollen, and healthy trees more than 8 inches through are generally left alone. The twig girdler and twig pruner cut the twigs of shagbark hickory (Carya ovata) and pecan (Carya illinoinensis) so the ends drop; the elderberry borer lives out its larval life inside the stems of black elderberry (Sambucus canadensis).

The emerald ash borer is what a borer looks like without that shared history. Since it arrived from Asia near Detroit in the 1990s it has killed ash trees, which had never met it, by the hundreds of millions. In a common garden at Michigan State University planted in 2007, every black ash was dead by 2013, while blue ash (Fraxinus quadrangulata) was barely colonized and still healthy in 2022; its phloem carries hard cells and phenolics the larvae do poorly in. It is the only ash we grow.

Flies, beetles and wasps at the flowers

Bees get the credit and their own article, but flies, beetles and wasps do a good share of the pollination in a native planting. Pawpaw (Asimina triloba) is pollinated by flies and beetles; its stigma ripens before its own pollen and the trees are self-incompatible, so growers plant two unrelated trees and sometimes hand-pollinate. Flower flies, the hoverers that pass for small bees, live on pollen and nectar while their larvae eat aphids, and paper wasps drink nectar between hunting trips and pollinate as they go.

Predators and parasitoids

Everything above is prey. A paper wasp colony catches thousands of insects in a season, caterpillars among them, and feeds them to its larvae. Lacewing larvae (the aphid lions) and the alligator-shaped larvae of lady beetles clear aphid and scale colonies; assassin bugs impale caterpillars and beetles on a beak; ground beetles hunt the litter at night. Then the parasitoids, most of the wasps and many of the flies: a braconid lays her eggs inside a living caterpillar, and her larvae eat it from within before spinning cocoons on its skin; the swollen tan aphid “mummies” in any colony are the work of others; tachinid flies lay their eggs on or in beetles, bugs and caterpillars. Many adult parasitoids feed on nectar, so the shrubs and flowers under the trees keep them close. The University of Maryland’s advice for aphids on a tree is to look for mummies first; they mean the work is being done.

Dead wood, leaf litter and the soil

Much of what a tree feeds, it feeds after death. A standing dead tree is bored by longhorn, jewel and bark beetles, and their tunnels become the nests of mason bees, leafcutter bees and aphid-hunting wasps. A fallen log shelters ground beetles and spiders under its bark, and once it has rotted about two years the bess beetles move in: inch-and-a-half black beetles that live in family groups in oak, hickory and maple logs, tunnel the wood and chew it for their larvae. Stag beetle larvae spend several years in fallen dead trees, and no healthy hardwood forest in Kentucky is without them, its entomologists say; termites and carpenter ants live in the same wood, and stag beetles alone feed birds, toads, raccoons and skunks. The old-growth article counts snags and logs as structure; the habitat article says leave the wood where it falls.

The litter is the densest animal community on the property: about 250,000 mites can live in a square meter of moist forest soil, with springtails, millipedes and snails. Fireflies are litter animals. Nearly 170 species are described from the United States and Canada, and most of a life that runs two or three years in the North is spent as a larva in leaf litter, soil or rotting wood hunting snails, slugs and earthworms; pupation is underground, in rotting logs or, for one genus, in the bark furrows of big oaks, hickories and tulip poplars. Of 132 North American species assessed against the Red List criteria in 2021, at least 18 are threatened and more than half could not be judged for lack of data. Leaf litter, not wood chips, is the rule under the canopy. Its ants carry the spring flowers: bloodroot, trilliums, violets and wild ginger fit each seed with a fatty attachment, and the ants haul the seed home, eat the attachment and drop the seed in a waste pile, where it grows. Salamanders and toads hunt the same layer; see the wildlife article.

The trees and shrubs that matter most

Only the caterpillars have been counted plant by plant, so a ranking leans on them. The National Wildlife Federation’s figures for the Eastern Temperate Forests run: oaks 436 caterpillar species, cherries and plums 340, willows 289, birches 284, poplars 249, maples 238, crabapples 237, blueberries 217, hickories 213, pines 200, alders 173, elms 164, basswood 132, walnuts 125, chestnuts 115, hazels 108, dogwoods 98, serviceberries 92.

• Oaks. First by every measure above. We grow eight, from dwarf chinquapin oak (Quercus prinoides) and bear oak (Quercus ilicifolia) for a small dry lot to swamp chestnut oak (Quercus michauxii), overcup oak (Quercus lyrata) and cherrybark oak (Quercus pagoda) for wet ground.
• Cherries and plums. The counts are by genus, and black cherry, the big native member of it, is one we do not sell; American plum (Prunus americana) and beach plum (Prunus maritima) share in the 340.
• Willows, birches, poplars, maples, pines and elms. Six of the top twelve genera. Sweet birch (Betula lenta) is the one we grow; willows alone host 289 caterpillar species, more than anything we sell but an oak or a plum.
• Hickories and walnuts. Shagbark hickory, pecan and black walnut (Juglans nigra).
• Alder, basswood, hazel, chestnut. Smooth alder (Alnus serrulata); American basswood (Tilia americana); American hazelnut (Corylus americana); Allegheny chinquapin (Castanea pumila), the native chestnut, which Chinese chestnut is not.
• Crabapple, dogwoods, serviceberries. American crabapple (Malus coronaria), flowering dogwood (Cornus florida), silky dogwood, downy serviceberry (Amelanchier arborea) and Allegheny serviceberry (Amelanchier laevis).
• The specialists’ plants. Black locust, American holly, witch hazel, pawpaw, black elderberry and ninebark, each a piece of the web found nowhere else.

Pesticides, lights and the other ways to undo it

Mosquito spraying is the commonest way a good planting is wasted. When the Xerces Society tested yards after treatments, residues were high enough to kill bees and butterflies, and 75 percent of the samples from nearby unsprayed yards were contaminated by a neighbor’s spray. Emptying buckets, gutters and birdbaths weekly does more than a truck. Nursery stock is the second route: systemic insecticides, neonicotinoids among them, move into a plant’s pollen and nectar; they reach higher concentrations and last longer in woody plants, and residues have been found months to years after a soil drench or trunk injection. “Bee-friendly” on a tag has no legal definition. Ask what was applied, and prefer seed-grown plants from a grower who can answer.

Light is the third. About 30 to 40 percent of the insects that fly to a street lamp die soon after, and at least 80 percent of the firefly species in the United States and Canada find their mates by light signals at dusk or after dark. Turn outdoor lights off in summer; where one is needed, make it shielded, on a motion sensor and red or amber rather than blue-white. Then the smaller things. Leave an unmown strip, since tall grass shelters butterflies, moths, fireflies and lacewings. Clear the invasive shrubs and vines, which feed little and shade out what does.

Where to start

• Plant an oak, and under it a plum, a hickory, a dogwood or serviceberry and a shrub layer of hazelnut, elderberry, viburnum and witch hazel: a species for each guild.
• Choose seed-grown, green-leaved species over cultivars, and ask any nursery, us included, what insecticides its plants have seen.
• Leave the leaves under the drip line and the logs where they fall; leave a snag standing where it threatens nothing; build a brush pile.
• Do not spray for mosquitoes; empty standing water weekly instead.
• Turn the lights off at night from May to September.
• Leave the galls, the mummies and the chewed leaves alone. A tree with holes in its leaves is a tree that is working.

Sources

• Keystone Native Plants: Eastern Temperate Forests, Ecoregion 8: National Wildlife Federation, from Tallamy’s host records: the 96 percent of terrestrial birds that rely on insects, and the caterpillar counts by genus (oaks 436, cherries and plums 340, willows 289 and the rest of the ranking).
• Nonnative plants reduce population growth of an insectivorous bird: Narango, Tallamy and Marra, Proceedings of the National Academy of Sciences 115 (2018), via PubMed Central: Carolina chickadees in Washington, DC yards sustained their population only where non-native plants were under 30 percent of plant biomass.
• More than 75 percent decline over 27 years in total flying insect biomass in protected areas: Hallmann and others, PLOS ONE 12 (2017): Malaise traps in 63 German protected areas, 1989 to 2016, recorded a 76 percent seasonal and 82 percent midsummer fall in flying insect biomass.
• Insect decline in the Anthropocene: Death by a thousand cuts: Wagner and others, Proceedings of the National Academy of Sciences 118 (2021), via PubMed Central: reported declines commonly around 1 to 2 percent a year and the causes, insecticides and light at night among them.
• The global distribution of diet breadth in insect herbivores: Forister and others, Proceedings of the National Academy of Sciences 112 (2015), via PubMed Central: more than 7,500 herbivorous insect species at 17 sites; on average 69 percent of caterpillar species feed on a single plant family, about 60 percent outside the tropics.
• Few keystone plant genera support the majority of Lepidoptera species: Narango, Tallamy and Shropshire, Nature Communications 11 (2020): about 14 percent of native plant genera support more than 90 percent of butterfly and moth species, with oaks, willows, cherries, pines and poplars at the top.
• Why Native Plants Matter: National Audubon Society: over 6,000 caterpillars to raise one brood of chickadees; native oaks host over 500 caterpillar species and ginkgo 5.
• The Arthropod Associates of 155 North American Cynipid Oak Galls: Ward and others, Zoological Studies 61 (2022), via PubMed Central: more than 700 of about 1,000 oak gall wasp species are North American; 151,075 arthropods reared from 155 gall types out of more than half a million galls from 32 oak species; 15 to 25 species per gall type.
• Periodical Cicada: Penn State Extension: nymphs 2 to 24 inches deep feeding on root sap for 13 or 17 years, 400 to 600 eggs per female, oaks, maples and apples preferred, netting for trees under 10 feet, and the birds and fish that gorge on adults.
• White Oak, Silvics of North America: USDA Forest Service: the insects of white oak, from oakworms, leaf tiers and walkingsticks to the two-lined chestnut borer, golden oak scale, acorn weevils and the cynipid wasps that gall acorns.
• Nesting and Overwintering Habitat for Pollinators and Other Beneficial Insects: Xerces Society: snags bored by longhorn, jewel and bark beetles whose tunnels house mason and leafcutter bees; logs, brush piles, leaf litter and unmown grass as shelter for ground beetles, fireflies, lacewings and overwintering moths and butterflies.
• Conserving the Jewels of the Night: Guidelines for Protecting Fireflies in the United States and Canada: Xerces Society (2019): nearly 170 firefly species; a life cycle of up to two or three years spent mostly as larvae in leaf litter, soil and rotting wood hunting snails, slugs and earthworms; pupation in rotting logs and bark furrows; leave the leaves and keep nights dark.
• The impact of artificial light at night on nocturnal insects: A review and synthesis: Owens and Lewis, Ecology and Evolution 8 (2018), via PubMed Central: about 30 to 40 percent of insects that approach a street lamp die soon after, and long-wavelength amber to red light is least disruptive.
• Smart Mosquito Management at Home: Xerces Society brochure (2026): yards tested after mosquito treatments carried insecticide at levels high enough to kill bees and butterflies, insecticide drifting into unsprayed neighboring yards, and emptying standing water weekly as the alternative.
• Study: Pesticide Sprays for Mosquitos May Kill Pollinators, Drift into Neighboring Yards: Xerces Society press release on the 2025 Stacks Journal study: every yard sprayed by a private mosquito company carried pyrethroid residues above the honey bee lethal dose, and 75 percent of samples from neighboring yards were contaminated.