Sphex ichneumoneus (Great Golden Digger Wasp)
Overview
Scientific name: Sphex ichneumoneus
Common name: Great Golden Digger Wasp
Family: Sphecidae (Thread-waisted wasps)
Range: Widespread in North America—southern Canada through most of the United States into Central America.
Habitat: Meadows, prairies, open woodlands, gardens—especially areas with sandy or loose soil for nesting and abundant nectar sources.
Appearance: Large (20–25 mm), slender wasp with a reddish-orange thorax, golden hairs on the thorax, and black abdomen with orange wings.
Life Cycle and Behavior
Emergence: Adults appear in midsummer (July–September).
Nesting: Females dig burrows in sandy or loose soils, often in open sunny areas.
Hunting/Provisioning:
Females paralyze katydids and grasshoppers (Orthoptera) and place them in the burrow as food for larvae.
One to several prey items are placed per chamber; an egg is laid on the paralyzed insect.
Larvae: Feed on the live but immobilized prey until pupation.
Overwintering: The species overwinters in the pupal stage, emerging the following summer.
Ecological Role
1. Predator / Natural Pest Control
Reduces populations of katydids and grasshoppers, which are herbivores of native plants and crops.
Helps maintain balance in grassland ecosystems by limiting orthopteran outbreaks.
2. Pollinator
Adults feed exclusively on flower nectar and are important pollinators for a wide range of prairie wildflowers.
Frequently visit flowers with easily accessible nectar (composites, mints, milkweeds).
3. Soil Aerator
Burrowing behavior aerates soil, aiding water infiltration and nutrient cycling.
4. Prey for Higher Trophic Levels
Serves as food for birds, spiders, and predatory insects; their nests may be parasitized by cuckoo wasps or bee flies.
Best Native Plants to Support Sphex ichneumoneus
Larvae:
Do not feed on plants directly but require habitats supporting katydids and grasshoppers—this means native grasses and forbs that sustain orthopteran populations.
Adults (nectar feeders):
Need abundant mid-to-late summer nectar plants in open sunny areas.
Key Nectar Plants (Mid–Late Summer Bloom)
Mints (Lamiaceae)
Mountain mint (Pycnanthemum muticum, P. virginianum) – Top attractor for digger wasps and many pollinators.
Wild bergamot (Monarda fistulosa) – Long bloom period, thrives in dry to medium soils.
Composites (Asteraceae)
Blazing stars (Liatris spp.) – Dense nectar spikes mid-late summer.
Goldenrods (Solidago spp.) – Crucial late-season nectar.
Aromatic and New England asters (Symphyotrichum oblongifolium, S. novae-angliae) – Fall-blooming nectar sources.
Milkweeds (Apocynaceae)
Butterfly milkweed (A. tuberosa)
(Provide midsummer nectar; also support monarchs.)
Legumes (Fabaceae)
White prairie clover (Dalea candida)
(Supports both nectar needs and grasshopper prey populations.)
Habitat Recommendations
Open, Sunny Spaces with Bare Soil
Loose, sandy or loamy soil for burrow nesting.
Avoid excessive mulch or dense turf grass.
Prairie Plant Diversity
Mix of nectar-rich forbs and native grasses (little bluestem, prairie dropseed) to support katydid prey populations.
Continuous Bloom
Sequence nectar plants to provide food from June–September.
No Pesticides
Insecticides harm wasps, their prey, and nectar plants.
Structural Diversity
Mix tall flowering plants with low grasses to create foraging and nesting habitat.
Ecological Significance
Pollinator: Vital for prairies and meadows, visiting a wide range of native flowers.
Predator: Controls orthopterans naturally without harming ecosystems.
Indicator species: Their presence signals healthy sandy soils and diverse prairie habitats.
Beneficial insect: Harmless to humans (rarely stings unless handled).
Conservation Notes
Populations benefit from:
Native prairie restoration.
Maintaining open soil patches for nesting.
Planting diverse nectar plants blooming mid- to late-summer.
Declines can occur with:
Habitat loss (conversion to turf grass or development).
Pesticide use.
Loss of prey (katydids/grasshoppers) due to lack of native vegetation.
