[2026] Top 5 Insect Mats & Fungal Substrate Bottles | Tips for Raising Large Specimens

[2026] Top 5 Insect Mats & Fungal Substrate Bottles | Complete Guide to the Basics of Breeding Beetle & Stag Beetle Larvae

When breeding beetle and stag beetle larvae, "what to feed them" is the most critical factor determining the size and health of the adult insect. It's also a common stumbling point for beginners, and many people wonder, "Should I choose a mat or a fungal substrate bottle?" In this article, we'll clearly explain the differences between the two, and introduce five carefully selected recommended products as of 2026.

Additionally, when purchasing healthy specimens, it's reassuring to keep our emergency first aid guide for living insects in mind.

---

What's the Difference Between Mats and Fungal Substrate Bottles?

Larval rearing substrates (food) are broadly divided into two types: "fermented mats" and "fungal substrate bottles." Neither is inherently correct—the key is to choose based on the species you're raising and your breeding goals.

Fermented Mats

This is sawdust from broadleaf trees or leaf mold fermented and matured using microorganisms. It's suitable for beetles in general and can be used both as a spawning bed and a larval rearing substrate. The relatively low price and ease of management make it ideal for beginners. Depending on the degree of fermentation, varieties include "unfermented (white chip)," "first fermentation," and "second fermentation (fully matured)," and you should choose based on the species and purpose.

Fungal Substrate Bottles

These are rearing bottles designed specifically for stag beetle larvae, with mushroom mycelium cultivated in sawdust. The mycelium breaks down the cellulose in sawdust into more easily digestible forms, allowing larvae to absorb nutrients efficiently. Compared to mats, the key advantage is faster growth speed and the ease of raising larger specimens. However, deterioration of the mycelium can damage larvae, so regular condition checks are necessary.