Gromphadorhina portentosa – Large Nymphs x12

Gromphadorhina portentosa, commonly known as the Madagascar hissing cockroach or giant Madagascar hissing cockroach, is one of the most impressive and recognizable ornamental cockroaches available to insect keepers. Native to Madagascar, this large, wingless species is completely different from the small household cockroaches that are commonly associated with pests. It is a fascinating exotic invertebrate, appreciated by collectors, educators and breeders for its size, behaviour, distinctive appearance and remarkable life cycle.

This species belongs to the family Blaberidae and is naturally associated with the forest floor of Madagascar, where it lives among leaf litter, fallen vegetation, rotten wood and other organic material. It is primarily active at night and feeds on plant material and other organic matter. In captivity, Gromphadorhina portentosa is one of the most popular ornamental cockroach species because it combines an impressive adult size with relatively straightforward care requirements.

A spectacular ornamental cockroach

Adult Gromphadorhina portentosa can reach approximately 6–10 cm in length, with females generally having a broader body. They have a robust, shiny exoskeleton with dark brown to almost black areas and warmer brown, orange or reddish tones on the abdomen. Unlike many other cockroach species, they are completely wingless, making them particularly easy to observe and handle compared with flying insects. Their slow movements and generally calm behaviour have also contributed to their popularity as educational and display animals.

One of the most characteristic features of this species is its famous hissing sound. Gromphadorhina portentosa produces the sound by forcing air through its abdominal spiracles rather than by rubbing its body parts together. Hissing can occur when the animal is disturbed or threatened, but it also plays a role in communication, courtship and interactions between males. Adult males can be distinguished by the prominent horn-like projections on the pronotum, which are much less developed or absent in females.

For insect enthusiasts, this makes the Madagascar hissing cockroach much more than a simple feeder insect. It is a genuine ornamental and display species, capable of becoming a long-term part of an invertebrate collection. Captive individuals can live for several years, with published sources generally reporting a lifespan of around 2–5 years under suitable conditions.

Life cycle of Gromphadorhina portentosa

The life cycle of Gromphadorhina portentosa is particularly interesting because, like other cockroaches with incomplete metamorphosis, it does not have a larval and pupal stage. The basic development consists of nymph, successive moults and adult.

Newborn nymphs already resemble miniature versions of the adults, although they are considerably smaller and immature. As they grow, they periodically shed their exoskeleton in a process known as moulting. Under favourable conditions, development from newborn nymph to sexually mature adult can take approximately 6–7 months, although growth rate varies according to temperature, nutrition and general husbandry conditions.

Reproduction is one of the most unusual aspects of this species. Female Gromphadorhina portentosa are ovoviviparous: after mating, the developing eggs remain inside the female in an ootheca rather than being deposited externally. The female retains the ootheca and the developing embryos until the young are ready to emerge. After a gestation period of approximately two months, she gives birth to live nymphs. Brood size can vary considerably, with sources reporting approximately 15–60 nymphs per reproductive event.

This reproductive strategy makes the species particularly interesting to observe in a breeding colony. Once a group is established and maintained in warm, stable conditions, reproduction can occur readily, making population management an important part of responsible husbandry.

Basic care guide

Gromphadorhina portentosa is considered a relatively easy ornamental cockroach to keep, making it suitable for both beginners and experienced invertebrate keepers. The most important factors are secure housing, adequate ventilation, suitable temperature, access to moisture and a varied diet.

A secure enclosure is essential. Although adult Madagascar hissing cockroaches are wingless, they are capable climbers, and young nymphs can exploit surprisingly small gaps. The enclosure should therefore have a secure lid and good ventilation. Providing pieces of cork bark, cardboard egg trays, tubes or similar structures creates hiding places and increases the available surface area.

For active growth and reproduction, temperatures around 24–28°C are commonly used in captive husbandry. At lower temperatures the animals can remain alive but their metabolism, activity and reproduction slow considerably. A moderate humidity level is appropriate, with good ventilation being particularly important to prevent stagnant, excessively wet conditions.

The diet can be based on a combination of fresh fruit and vegetables together with a suitable dry food. The species is naturally associated with plant and decomposing organic material, and captive colonies generally thrive on a varied diet. Fresh food should be replaced regularly to prevent mould and excessive humidity inside the enclosure.

During moulting, nymphs should be left undisturbed. Providing suitable humidity and enough vertical surfaces or textured material allows them to position themselves safely while the new exoskeleton hardens.

Gromphadorhina portentosa Large Nymphs x12

This product contains 12 large Gromphadorhina portentosa nymphs, supplied as ornamental cockroaches for keeping, observation and breeding.

Starting with large nymphs offers an excellent opportunity to watch the species develop through its remaining moults before reaching adulthood. As they mature, their characteristic body shape and coloration become increasingly pronounced, while males will eventually develop the distinctive pronotal projections associated with the species.

Whether you are starting your first ornamental cockroach colony, expanding an existing insect collection, looking for an unusual educational animal or simply want to experience one of Madagascar’s most iconic invertebrates, Gromphadorhina portentosa is a fascinating species with an exceptionally interesting biology.

Species: Gromphadorhina portentosa
Common name: Madagascar Hissing Cockroach / Giant Madagascar Hissing Cockroach
Product: 12 large nymphs
Type: Ornamental cockroach
Origin: Madagascar
Adult size: approximately 6–10 cm
Development: incomplete metamorphosis
Reproduction: ovoviviparous
Sexual maturity: approximately 6–7 months under favourable conditions
Lifespan: approximately 2–5 years
Difficulty: Easy
Activity: Mainly nocturnal
Wings: Absent
Diet: Fruit, vegetables and suitable dry food