Notable concerns
- Northern black widow (rare, southern counties)
Medically significant species in Michigan
| Species | Scientific | Significance | Range note |
|---|---|---|---|
| Yellow Sac Spider | Cheiracanthium inclusum | Moderate | Throughout the continental United States and southern Canada. |
All documented species in this index
Species below are present in Michigan according to extension publications and the rangeStates records in our species index. Click through for full profiles.
- Yellow Sac Spider - Cheiracanthium inclusum (Moderate)
- Common House Spider - Parasteatoda tepidariorum (Low)
- Wolf Spider - Lycosidae (family overview) (Low)
- Cellar Spider - Pholcus phalangioides (Not medically significant)
- Bold Jumping Spider - Phidippus audax (Low)
- Yellow Garden Spider - Argiope aurantia (Not medically significant)
- Grass Spider - Agelenopsis spp. (Not medically significant)
Seasonal activity in Michigan
Spider activity in Michigan follows the documented peak season of May–September. Indoor sightings often spike in late summer and early fall as males wander to find mates and as cooling outdoor temperatures push synanthropic species toward heated structures.
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Highlighted months reflect the state extension peak-activity window. Individual species (especially indoor recluse populations) may be active outside this range.
Prevention checklist for Michigan homes
- Seal exterior gaps wider than 1/8 inch around utility penetrations, dryer vents, and weep holes. Install door sweeps on garage and basement entries.
- Reduce harborage by storing firewood, lumber, and seldom-used boxes off the ground and at least 18 inches from foundation walls.
- Vacuum webs, egg sacs, and spiders rather than spraying. Mechanical removal outperforms most over-the-counter residual sprays for synanthropic species.
If you are bitten
Nearby states in the Midwest region
- Spiders of Illinois - peak activity may–october
- Spiders of Indiana - peak activity may–october
- Spiders of Iowa - peak activity may–september
- Spiders of Minnesota - peak activity june–august
- Spiders of Missouri - peak activity april–october
- Spiders of Ohio - peak activity may–september
- Spiders of Wisconsin - peak activity may–september
Sources
- [1]MSU spider identification - MSU Cooperative Extension. Accessed 2026-06-14.
- [2]Spiders and scorpions submitted as suspected brown recluse - Vetter RS, 2008. Accessed 2026-06-14.