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Care Guide Series 1:

Beetles

Care Guide 1.1:

Beetle life cycles

Written by Mark Nelson

Introduction

Beetles are by far my favourite taxa. The Beetle order (Coleoptera) contains over 350,000 species worldwide. They represent around 40% of all insects. There are so many varietiesof beetles, many of which display incredible colours and patterns for frightening away predators. Many also possess fascinating horn structures for attracting females. The most commonly kept varieties of beetle in captivity are flower beetles (Cetonidae), rhinoceros beetles (Dynastidae) the Stag beetles (Lucanidae). These are the three subfamilies that we will be taking a particular interest in, especially flower beetles, as this is the subfamily we keep and breed the most specimens of. In this care guide we will be explaining the different stages within the beetle life cycles, so you can better understand these magnificent creatures. 

The beetle life cycle consists of 4 Stages; egg, larvae, pupae and imago. The entire lifecycle will last a different amount of time depending on the species. Here we aim to give you a general overview focusing primarily on flower, rhinoceros and stag beetles. 

Stage 1: The Egg 

The female, once mated, will begin to find a suitable place for depositing her eggs. This 'suitable place' will vary from one subfamily to another. For example, flower beetles will happily lay their eggs in decaying leaf matter. Whereas, the females of stag beetles will burry in search of rotten wood. Upon finding a suitable piece of rotting wood, they chew tiny holes in the side in which they deposit a single egg before packing the whole back up with small fragments of wood. Then the move on and repeat the process all over again. Some may only lay a few dozen eggs. Whereas others are capable of laying hundreds of eggs in their lifetimes. The length of time it takes for the eggs to hatch will vary a lot from one species to another. When the egg does eventually hatch then it has reached the second stage of its life cycle, the larvae. 

Picture 1: Mecynorrhina harrisi egg set up to avoid cannibalism - egg was covered with soil after photo

Picture 2: Eggs collected from our large colony of Mecynorrhina torquatus ugandensis 

Stage 2: The Larvae

When the larvae hatches from the egg, this marks the first stage, also referred to as the 1st instar. As beetle larvae develop they must shed their skin in order to grow. Each time they shed their skin they grow a little bit bigger. The larvae then eats and gains weight before shedding its skin for the first time, at which point it becomes a second instar. Then it will continue to eat and gain weight before shedding for a second time into the third instar. This is the longest stage of the larval development and can last just a few months for the simpler, smaller species, to several years for some of the larger more complex species. During the third and final instar the larvae will slowly gain weight consuming as much substrate as possible. The more weight it gains, the larger and stronger it will be when it eventually develops into an adult beetle. The larvae of some of the world's largest beetles can have a final weight of up to 150g!

Stage 3: The Pupae

 

There will come a point when the larvae become a much darker yellowish colour. Shortly after, it will construct a chamber in the soil where it will shed its skin for the last time and develop into the pupae. Some species construct stronger chambers than others. Flower beetles will construct a strong cocoon made of soil in which they pupate. Whereas, stag and rhino beetles make chambers in the soil which are much flimsier, and often collapse if disturbed. During the pupae stage the larvae breaks down and slowly transforms into the different parts of the adult beetle. This process is called metamorphosis and can last several weeks or months depending on the species.

Picture 3: Male Mecynorrhina torquatus ugandensis pupae inside its cocoon

Picture 5: Female Xylotrupes gideon pupae 

Picture 6: Male Xylotrupes gideon pupae 

Stage 4: The Imago (Adult)

 

Once metamorphosis is complete the adult beetle will emerge from the pupae. Its wing cases will form properly and harden, which is a process that may take a few days. The adult beetle will then have an inactive stage where it sits and waits inside its chamber/cocoon, sometimes for several months depending on the species. They will then emerge completely when conditions become more favourable. The adult beetle will then make its way to the surface of the substrate where it will find food, mate and the life cycle will then start all over again.

Xylotrupes_edited.jpg

Picture 7: Male Xylotrupes gideon 

Thank you for reading! If you have any questions please feel free to send us a message via our contact us page!

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