Life Cycle

The Therea olegrandjeani is a terrestrial burrower of the Indian dry forests. In the wild, the question mark roaches dig under the dry and loose soil of these forests; the soil is often topped by dried leaves as well, and these help cover the question mark roaches so they are not easily found by their natural predators.

Question mark roaches are long-lived for their size. The ootheca or eggs of the question mark roach look like seeds on the dry forest floor. Generally, their eggs hatch somewhere around 90 days, and the nymphs (juvenile roaches) reach adulthood within two years; however, when kept in captivity in the Philippines, they can reach adulthood within nine months with frequent
feeding of protein-rich food, fruits, and vegetables.

Nymphs are just 3 millimeters (mm) in length when they hatch from the ootheca and are gray in color when they emerge; they turn black after a molt. The adult size of the question mark roach ranges from 20-30 mm in body length, with males being smaller than the females. Adult question mark roaches only live for 3-5 months after their ultimate molt and breed several times throughout adulthood. The Therea olegrandjeani only has the question mark pattern on its back when they reach adulthood; nymphs and juveniles are pure black.

What We Know About Them

Not much is known about the question mark roach since very little research has been done on them after their identification. But here’s what we do know from observing them in captivity. Question mark roaches are climbers, even if their bodies are generally built for burrowing, with their thick exoskeleton on their backs.

This must have been an evolutionary modification since it will be easier to escape from natural predators when an animal has multiple escape routes to choose from.

Loose substrate is the commonly used substrate for keepers who have these roaches in captivity; this mimics their environment in the wild. Dried leaves, twigs, and moss are usually added to make the terrarium more appealing and so that question mark roaches can thrive more comfortably as this mimics their natural habitat.

Nymphs and juveniles of question mark roaches are subterranean and prefer the zone between the litter and humus of the soil in the wild while adults are often in burrows.

Some question mark roaches have been recorded with different patterns on
their backs. This has been proven to be a product of selective line breeding of individuals in captivity.

Question mark roaches are monandrous (preferring a single male mate while rejecting all others) like its cousin, the Therea petiveriana, also known as the Domino Roach.

Most of these roaches rely on tactile or chemical cues to find their mate, which helps prevent hybridization or the interbreeding of different species with one another. Thus, even if different members of the Therea sp. Are kept together in the same terrarium in captivity, they will not create a hybrid because of the different tactile and chemical cues emitted by each species is
different, and will not be recognized by other species of the same genus.

There has been no record or reports of a Therea sp. hybrid. Even in the wild, where the different members of the Therea sp. have overlapping habitats, they do not interbreed. Tactile cues are often the vibrations emitted by and individually felt in the substrate; each species has a vibration made unique by their gait. For their chemical cues, pheromones are released so they can
easily attract a mate. In contrary, a few species of roaches rely on acoustic (sound) signals and visual cues to attract a mate.

Why Not Keep It as a Pet?

The question mark roach is a good-looking pet roach even though it can be difficult to see when they are young, since they are dark colored to easily blend with their substrate. They are very rewarding pets to observe when they reach adulthood, especially with the unique coloration that sets them apart from other roaches. Many other Therea sp. have good coloration as well;
however, they are still rare or have not yet reached the Philippines yet.

Nature is really beautiful. Who could imagine the ordinary house cockroach would have a very pretty cousin such as the Therea olegrandjeani?

Some people mistake the question mark roach for beetles, which simply drives home the point that there are still many things that need to be discovered about this species. Keeping one is a great experience, especially when observing their behavior firsthand. This pet roach is definitely a must-have for every roach enthusiast.

This appeared as “It’s the What Cockroach?” in Animal Scene’s September 2015 issue.