Difference Between Water Bug and Cockroach

Water Bug vs Cockroach

It is rather difficult to mix up water bugs with cockroaches, despite the common reference of cockroaches as water bugs. As the common names imply they live in different ecosystems. Additionally, their ecological roles are different to each other. With some more important differences, including the external appearance water bugs differ from cockroaches. This article presents information on both these insects and explores the differences between them.

Water Bug

There are few types of insects referred as water bugs, but only the true water bugs are considered in this article. True water bugs belong to the Infraorder: Neomorpha of the Order: Hemiptera. They are referred as true water bugs, as their habitat being water. The earliest fossil of a water bug dates back to 250 million years. Currently, there are about 2,000 water bug species, and they are distributed all over the world except in the Polar Regions. The majority of true water bugs live in freshwaters while there are some brackish water and saltwater species, as well. They to be hemipterans, their forewing is hardened anteriorly but not the posterior half. The ocelli are absent in water bugs, but sometimes those are vestigial. Water bugs are usually omnivorous insects, and they feed on both plant matter and prey upon small invertebrates and small larvae of amphibians. However, there are some giant water bug species with the capability of preying upon some fish and amphibian species.


Cockroaches are a highly diversified group of insects with more than 4,500 species, and they are classified under the Order: Blattodea. There are eight families of cockroaches, but only four species have become serious pests. However, about 30 species of cockroaches have been living around the human habitations. The most important aspect of the cockroaches is that their ability to withstand the mass extinctions. In a simple term, cockroaches have never failed to survive any of the mass extinctions taken place on the Earth since their beginning 354 million years ago, in the Carboniferous period. Compared to most of the other insects, cockroaches are large with about 15 – 30 millimetres long body. The largest recorded species is the Australian giant burrowing cockroach with about a nine-centimetre long body. They all have a dorso-ventrally flattened body with a small head. The mouthparts are adapted to feed on any type of food, which is an indication of their generalised food habits. Therefore, whatever is available could be food for cockroaches. Their basis of survival through more than 350 million years is well explained using their generalised food habits. They have large compound eyes and two long antennae. The whole body is not as hard as in many insects, but the first pair of wings is hard and the second pair is membranous. Their legs have coxae and claws for protection and other functions. Cockroaches could be serious pests not only for food destroyers, but also as dispersal agents of diseases such as asthma.


What is the difference between Water Bug and Cockroach?

• Cockroaches are more diversified than water bugs.

• Cockroaches exist more than 100 million years before the water bugs did.

• Cockroaches are more generalised than water bugs are.

• The forewings are hardened fully in cockroaches, whereas only the anterior half of the forewings is hardened in water bugs.

• Cockroaches could be serious pests but not the water bugs.

• Body is dorso-ventrally flattened in cockroaches but not in water bugs.

• Cockroaches have a large pair of eyes, but the ocelli are vestigial or absent in water bugs.