Spider Beetle

(Mezium affine) Care Sheet

Overview

These odd little beetles may look like miniature spiders at first glance, but don’t worry, they’re not here to scare you. Mezium affine, commonly called the Spider Beetle, is a small, round-bodied beetle covered in fine hairs that give it a velvety sheen. They're nocturnal, super low-maintenance, and a fun oddity to add to any invertebrate collection.

Size & Lifespan

• Adult Size: ~2–3 mm (yes, they’re tiny!)
  
  

• Lifespan: 6–12 months average
  
  

• Activity: Nocturnal scavengers
  
  

• Behavior: Skittish, slow-moving, non-aggressive
  
  

Enclosure Setup

Recommended Tarantula Cribs Enclosures:
Due to their small size and escape artistry, these beetles do best in escape-proof acrylic enclosures with tight-fitting lids and minimal ventilation holes. Look for enclosures designed for micro species.

• Best Options:
  
  

• Cuboid Mini
  
  

• Slider Crib Mini
  
  

• 3” Tarantula Cube
  
  

• Small Slider Crib
  
  

• OG Sling Crib
  Available from Tarantula Cribs (use code TTC10 to save 10%).
  
  

Substrate:
I do not use a traditional substrate and have had a alot of luck keeping them on a mixture of rolled oats and dry dog food. They eat it, they hide in it, they burrow into the pieces of dog food. It is important to keep it dry or you will have mold issue and beetle die off.

Decor:
Add cork bark, leaf litter, and small pieces of egg crate or cardboard for shelter and surface area. These beetles are shy and love to hide in crevices. It is important to make sure any decor is not resting on or near the ventilation holes. In larger enclosures like the Tarantula Crib Medium Slider, the spider beetles can fit through the larger ventilation holes. They can not climb the smooth walls, but they can climb the decor and make an exit if you are not careful.

Temperature & Humidity

• Temperature: 68–75°F
  
  

• Humidity: around 50%, better drier than damp
  
  

• Lighting: No special lighting needed—ambient room light is fine. Keep them away from direct sun or intense heat.
  
  

Give them a slice of carrot or other vegetable and they will get their water needs from that.

NO WATER DISH!

Diet

Spider beetles are opportunistic scavengers and will eat just about anything organic. They prefer dry food sources.

Feeding Options:

• Dry dog or cat kibble (crushed)
  
  

• Fish flakes or reptile pellets
  
  

• Dried fruits (small amounts)
  
  

• Rolled oats, bran, or puffed rice
  
  

• Freeze-dried mealworms or crickets
  
  

Replace food every 3–4 days to prevent mold or mites. Remove uneaten soft foods promptly.

Interesting Facts

• Despite their name, spider beetles aren’t arachnids.
  
  

• They're often found in old houses, pantries, or natural history collections (they love dried stuff).
  
  

• These beetles can "play dead" when disturbed—don’t panic if one goes motionless for a while.
  
  

Handling & Behavior

You’ll rarely see them during the day, and they’re delicate, so handling isn’t recommended. Observe them under red light at night if you want to watch them in action. Escape risk is high due to their small size. Always check if the lids are secured.