Notable concerns
- Southern black widow (rare)
- Joro spider (recently documented)
Medically significant species in Maryland
| Species | Scientific | Significance | Range note |
|---|---|---|---|
| Southern Black Widow | Latrodectus mactans | Medically significant | Southeastern United States, from southern New York to Florida, west through Texas and into |
| Yellow Sac Spider | Cheiracanthium inclusum | Moderate | Throughout the continental United States and southern Canada. |
| Northern Black Widow | Latrodectus variolus | Medically significant | Eastern North America from southern Canada through New England and the Appalachian region |
All documented species in this index
Species below are present in Maryland according to extension publications and the rangeStates records in our species index. Click through for full profiles.
- Southern Black Widow - Latrodectus mactans (Medically significant)
- Yellow Sac Spider - Cheiracanthium inclusum (Moderate)
- Joro Spider - Trichonephila clavata (Not medically significant)
- Northern Black Widow - Latrodectus variolus (Medically significant)
- 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 Maryland
Spider activity in Maryland 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 Maryland 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.
- For widow-active areas, wear gloves when handling outdoor electrical boxes, irrigation valves, and stacked materials. Widows favor undisturbed voids.
- 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 Mid-Atlantic region
- Spiders of Delaware - peak activity may–september
- Spiders of New Jersey - peak activity may–september
- Spiders of Pennsylvania - peak activity may–september
- Spiders of Virginia - peak activity april–october
- Spiders of West Virginia - peak activity april–october
Sources
- [1]UMD spider identification - UMD Cooperative Extension. Accessed 2026-06-14.
- [2]Spiders and scorpions submitted as suspected brown recluse - Vetter RS, 2008. Accessed 2026-06-14.