# Pheropsophus (Bombardier Beetle)

Pheropsophus is a type of ground beetle, which is commonly known as the Bombardier beetle. There are hundreds of species of this beetle, including the genera Pheropsophus and Brachinus. They have mostly dark or black body types, but they might have some orange or yellow spots on the abdomen or thorax. Their legs are always yellow, with dark spots on the knees. They have long, distinct antennae that match the color of their legs. They can grow up to a length of 1 inch in size.
The taxonomy of the Bombardier beetle has been debated in recent years. The Pheropsophidius, Pheropsophus (the sister genus of Pheropsophidius), and Brachinus genera have been included in the subtribe Pheropsophina but it was later found that the Pheropsophidius genus originated from the Pheropsophus genus. This was caused by the splitting of Africa and South America, which has led to confusion over the taxonomy of the Bombardier beetle.
The Pheropsophus is known for its ability to shoot poison spray out of its rectum. This spray is a defense mechanism that the beetles use to kill other insects and to deter predators from coming close to them. The spray is made within their rectums when two chemicals combine to create this explosive poisonous spray.

## Habitat

The Pheropsophus can be found anywhere in the world except for Antarctica. They can be typically found in woodlands and grasslands. They like to hide under stones and leaf litter.

## Taxonomy

| Domain | Animalia |
| Phylum | Arthopoda |
| Class | Insecta |
| Order | Coleoptera |
| Family | Carabidae |
| Genus | Pheropsophus |

## Taxonomy History

The taxonomy of Pheropsophus has been debated and changed since 1970 between the genera Pheropsophidius and Pheropsophus. The Brachinus and Pheropsophidius genera are both part of the subtribe Pheropsophina. Pheropsophidius is only located in South America and Mexico. Pheropsophus is located in Africa, Asia, and Australia. After research was conducted on both genera, it is believed that the Pheropsophus genus was present in the mid-upper Cretaceous Age. They were present on multiple continents because the supercontinent Pangea had broken apart and was continuing to spread out during this time. Pheropsophidius is believed to have originated in Africa but moved to South America and Mexico. This allowed this genus to evolve differently than the Pheropsophus genus. Pheropsophidius and Pheropsophus are now classified as sister groups under the Pheropsophina subtribe. This means that previously classified Pheropsophidius beetles can now be classified as Pheropsophus beetles. This means that they are present all over the globe, except for Antarctica.

## Life Cycle and Diet

Bombardier beetles prefer to lay their eggs around wet, decaying plants. The eggs are fertilized by a sack of sperm from a male. Once the eggs hatch, the larvae go through molts at different life stages before becoming a full adult. The larvae of certain species of Pheropsophus survive mostly on mole cricket eggs and will not eat if not in a habitat that mimics mole cricket pits. Adults survive for a few weeks, eating young insects and detritus. They are useful for the decomposition of decayed plants in their habitats, which are near moist logs and leaf litter.
* Examples of things that Pheropsophus eat, including insects and detritus.

## Defense Mechanisms

The defense mechanism of Pheropsophus is the chemical spray they shoot out of their rectums to help them flee from a predator they feel threatened by. There are two different chemicals used to make the explosive spray. These chemicals are hydrogen peroxide and hydroquinone. The two chemicals are separated by two different sacks inside the body until the Pheropsophus feels threatened or a predator is near them. To create the explosive spray the two chemicals are released from the two sacks to combine and become very reactive. The chemical equation for hydrogen peroxide is ${\ce {H2O2}}$ and the chemical equation for hydroquinone is ${\ce {C6H6O2}}$. Once the two chemicals combine it forms benzoquinone, oxygen, and water, and is considered an exothermic reaction. The reactions that cause this are hydrogen peroxide: ${\ce {2H2O2 -> 2H2O + O2}}$ and hydroquinone:${\ce {C6H6O2}}$. The overall reaction that creates the benzoquinone is${\ce {C6H6O2 + H2O2 -> C6H4O2 + 2H2O}}$. This reaction can heat up to about 100$^o$C and can make a popping sound while exiting the rectum of the Pheropsophus.
Benzoquinone can lead to small burns and incapacitation for would-be predators. Also, the chemical spray they shoot can cause chemical burns, painful skin, and eye irritation, and can cause dermatitis in humans but it is not fatal to humans in any way. They can create 80 reactions with this chemical spray in four minutes because of the amount of hydrogen peroxide and hydroquinone they create in the sacks. Videos online show how quickly this reaction takes place to keep predators, such as praying mantises, away.

## Evolution and Behavior

Bombardier beetles are classified as winged insects but cannot effectively escape predators using their wings. This is because their wings are covered by a hard shell that has to be moved before they can take flight. These beetles developed their distinct acid spray through evolution to help escape predators. This spray gives them the time they need to use their wings to fly away.
They play both the predator and scavenger role in their environments. They feed on other insects but can also eat detritus, which makes them great for decomposition.