A lot of invertebrate heating advice is just reptile advice with the species names swapped out, and half of it does not apply. Invertebrates are ectothermic, yes, but their heating needs are genuinely different from a bearded dragon or a corn snake. Most of the tropical invertebrates in the UK hobby do well at 20-26C, which is close to normal room temperature in a heated house. You may not need supplemental heating at all.
Do you actually need it?
Honest answer: maybe not. If your house stays above 18C year-round, many commonly kept species will be perfectly fine without extra heat. Pachnoda marginata sun beetles, most Porcellio isopods, and several millipede species tolerate UK room temperatures, though they may develop more slowly than they would at 24C.
Where supplemental heating becomes necessary:
- Your house drops below 16-18C at night, particularly in winter. Prolonged cold slows metabolism, reduces breeding, and can kill tropical species.
- You are keeping species that need consistent warmth above 22C, such as Mecynorrhina beetle larvae or Cubaris isopods.
- You want to speed up beetle larval development. Warmer temperatures (within the species' safe range) produce faster growth, though sometimes at the expense of adult size.
- You keep animals in an unheated room, shed, or garage.
Heat mats
The most common heating method for invertebrates in the UK. A heat mat is a thin, flexible pad that produces gentle warmth. Stick it to the side or underneath the enclosure.
For invertebrates, I prefer side-mounting. When a heat mat sits under the enclosure, it heats the substrate from below. That sounds fine until you remember that many invertebrates burrow to escape heat and find cooler, moister conditions. If the bottom of the substrate is the warmest spot, burrowing species have nowhere cool to retreat to. Side-mounting lets the warmth radiate across the enclosure while keeping the lower substrate cool and damp.
A thermostat is not optional. An unregulated heat mat can reach 40-45C on its surface, which will cook anything in contact with it. Use a mat stat (on/off thermostat) at minimum. Place the probe inside the enclosure at the level where your animals spend time, not stuck to the outside of the glass.
Ceramic heat emitters
These screw into a standard lamp fitting and produce heat without light. They work well for larger enclosures or heated shelving units where you want ambient warmth. The downsides: they dry the air out fast, and they need a pulse-proportional or dimming thermostat (not a simple on/off mat stat) to regulate properly.
I use a ceramic heater for a shelving unit with several isopod colonies. It sits at the top and provides gentle background warmth across multiple tubs. With a thermostat probe hanging at shelf level, the whole unit stays at about 22-23C through winter.
Heat cables
Useful if you are heating a rack system or multiple enclosures. Heat cable runs along the back or underneath a row of tubs and can be controlled with a single thermostat. They are more flexible than heat mats for custom setups, but the installation takes a bit more thought.
What to avoid
Heat lamps. A basking lamp designed for reptiles produces intense, focused heat and light. Most invertebrates do not bask, and the radiant heat from above dries out substrate rapidly. Desiccation is a bigger threat to most invertebrates than cold. If you need overhead heating, a ceramic emitter without light is a better choice.
Heat rocks. These are relics from 1990s reptile keeping. They produce uneven, concentrated heat and have a reputation for burning animals. Nobody in the invertebrate hobby uses them, and you should not either.
Running any heat source without a thermostat. I have mentioned this twice already, and I will mention it again. A thermostat is cheap. A dead animal is permanent. There is no good reason to skip it.
Temperature and development
For beetle keepers in particular, temperature directly affects how larvae develop. Warmer conditions (24-26C) produce faster growth and shorter larval periods, but adult beetles may end up smaller. Cooler conditions (20-22C) slow development but can produce larger adults. Some breeders keep larvae cooler deliberately for this reason.
There is a floor, though. Below about 18C, most tropical beetle larvae slow down drastically, and prolonged cold below 15C can cause deaths. Find a temperature in the species' comfortable range and keep it stable. Wild swings between day and night temperatures stress animals more than a slightly suboptimal but consistent temperature.
Monitoring
A digital thermometer with a probe inside the enclosure is the minimum. The cheap stick-on LCD strip thermometers that come with starter kits are only accurate to within a few degrees, which is the difference between comfortable and dangerous for some species.
I use a probe thermometer in each enclosure and check it when I do my daily rounds. Some keepers use data loggers or smart thermometers that record min/max temperatures over time, which is useful if your house temperature fluctuates a lot overnight.
Practical setup
For a single enclosure, a small heat mat on the side wall with a mat stat set to 23-24C covers most tropical invertebrate species. The probe goes inside the enclosure, stuck to the wall at the midpoint height. The mat covers about a third of one wall, leaving the rest of the enclosure as a cooler zone.
For a shelving unit or rack, a ceramic emitter or heat cable on a thermostat is more cost-effective than individual mats on every tub. Position the heat source so the warmest shelf is at the top (heat rises) and put species that prefer it cooler on the lower shelves.
In summer, you probably will not need supplemental heating at all. In fact, UK heatwaves can push temperatures above 30C, which is too hot for most invertebrate species. Ventilation and moving enclosures away from direct sunlight becomes the priority in July and August.