Beetle Larva Care Sheet

How to Care for Beetle Larvae (Care Sheet)

This is part 1, of a four part care sheet that covers the breeding of beetles:
1. Beetle Larva Care Sheet
2. Beetle Adult Care Sheet
3. Beetle Breeding Guide
4. Beetle Egg Laying Guide

Trypoxylus dichotomus larvae on Flake Soil

Trypoxylus dichotomus larvae on Flake Soil

To raise a beetle larva (grub), all you need is a plastic container and suitable substrate. Substrate that can be used for rhino beetle larvae are decayed leaves, white-rot wood, or artificially fermented Flake Soil. Details on these substrates can be found in the Beetle Substrate Guide, and my personal recipe for homemade Flake Soil can be found in the Flake Soil Guide.

Growth Stages:
Rhino beetles have 4 distinct developmental stages which are the following:
Egg -> Larva (L1>L2>L3) -> Pupa -> Adult

Within the larval stage, there are also 3 separate stages called L1, L2 and L3 which essentially stands for “Larval Stage One/Two/Three”. Every time a larva sheds its skin to grow larger, the “L” number increases by one. So L1 larvae are individuals that have hatched from an egg and have not shed yet, L2 larvae are individuals that have shed once since hatching, and L3 larvae are individuals that have shed twice since hatching.

Container Size:
The container size and volume of substrate should be increased every time the larva sheds into the next L number. As a guide, the minimum volume per larva for average sized rhino beetle species such as Trypoxylus dichotomus should be the following:
L1 – 100 millilitres
L2 – 200 millilitres
L3 – 2000 millilitres

Temperature:
The temperature should be controlled according to the needs of the specific species, especially during hot summers or cold winters. Keep the container in a quiet place out of direct sunlight. For example, highland species such as Dynastes neptunus and Dynastes satanas should be raised between 15-20C, and lowland species such as Dynastes hercules and Chalcosoma caucasus should be raised between 20-25C.

Ventilation:
Ensure that there are several ventilation holes in the lid of the container to allow for the aeration so that the larva doesn’t suffocate. Care should also be taken not to add too big of a ventilation hole, or too many holes as this will increase the evaporation rate of water from the substrate which will dry it out quicker.

Humidity / Substrate Moisture:
Rhino beetle larvae will get all the moisture they require from the substrate they eat so there is no need to spray water daily like when raising other types of insects. This however means that the control of the moisture level of the substrate is of the utmost importance. It should be managed carefully to make sure that it does not dry out too much or is not kept too wet.

Substrate that is too dry will cause larvae to shrivel up from the lack of water and die from moisture loss, whilst substrate that is too wet will encourage the growth of bacteria and fungi that can be harmful to the larvae, as well as allowing the proliferation of mite and small flies. The way to check the moisture level of the substrate is to make a ball of substrate in your hand and squeeze hard. If water drips out of the ball when squeezed, the substrate is too wet. If the ball of substrate does not hold its shape and falls apart when released, the substrate is too dry. If the ball of substrate holds its shape and does not drip any water, it is the perfect moisture level.

Substrate Changes:
With rhino beetle larvae, it is easy to see when the substrate needs changing, as the eaten substrate is excreted in the form of small hard pellets. When there are a lot of these faecal pellets in the substrate, it is time to remove some of the old substrate and add in some new substrate, which will be outlined below.

  1. Tip out the contents of the container including the larva into a bucket.
  2. Do NOT throw away any of the old substrate yet.
  3. Place the larva somewhere safe and fill the original container 1/3 of the way up with the old substrate.
  4. Fill up the rest of the container with the new substrate (2/3).
  5. Make a small groove on the surface and place the larva in it so that it can dig down into the substrate.

The reason why it is imperative that a portion of the old substrate is added is because the bacteria and other microflora in the gut of larvae slowly adapt to digest the current substrate they are eating. When this gut bacteria is excreted as faecal pellets into the substrate they are in, the gut bacteria assimilate into the un-eaten substrate and essentially work as a pre-digestor which makes it easier for the larva to process the rest of the substrate.

Therefore the replacement of 100% of the old substrate with fresh substrate results in shock and stunted growth of the larva as their gut bacteria have to adapt again to the new microflora present in the fresh substrate. By keeping 1/3 of the old substrate and only adding in 2/3 of the fresh substrate to, the larva can slowly adapt to the new substrate over time.