Just Like Mum and Dad

Cockroaches are hemimetabolous insects, meaning that the young roughly resemble adults except for wings in winged species and for differences bewteen sexes where there is sexual dimorphism. There are no distinct stages in development. The nymphs molt as needed until they reach adulthood.

Neonates and freshly molted individuals are pale, lacking pigmentation. Since one that has just shed is particularly vulnerable to predation or injury, they tend to hide for a few hours while their cuticles darken. Notice the molting roach in the second picture below.

Cockroach nymphHissing cockroach molting

First picture: Nymph of Ellipsidion humerale; Photographer: Jean and Fred Hort, from the Encyclopedia of Life. Second picture: molting  Madagascar Hissing Cockroach, G. portentosa. Photo by Wendy Derjue-Holzer.

Reproduction and Parental Care

Sexual dimorphism in cockroaches varies widely. In some, the presence or absence of wings distinguish the sexes; in these usually males are active fliers and may have larger eyes, while the females are burrowers. Overall body size may also differ; generally speaking, males tend to be thinner in appearance than females. In some species, differences between the sexes are so dramatic that they have been classed as separate species in the past.

The large pronotum characteristic of cockroaches also varies. Sometimes there are rather dramatic differences in the pronota of males and females. One obvious example is the Madascar hissing cockroach Gromphadorhina portentosa, in which adult males have distinct humps (often described as horns) on their pronota, while the females have only small bumps. Males may use their humps to push each other around in competition for females or to show dominance, or perhaps for sexual attraction.

Cockroaches are considered among the most caring parents in the insect world. This care ranges from merely dropping the ootheca in a protected spot, to mothers staying with the neonates for a couple of hours, to both parents caring for the young for several years in a nest, and everything in between.

Gravid females produce oothecae or egg cases. Many, like the German cockroach shown in the right hand image below, simply drop their oothecae in convenient spots such as crevices and other protected areas, though some actively defend them. Some females dig shallow burrows for their oothecae, or even live underground where they and their nymphs are safe. Others, such as Gromphadorhina portentosa, retain their egg cases inside their bodies until the nymphs hatch (ovoviparity). Newly hatched G. portentosa nymphs are also provided with their first meal - the ootheca and accompanying secretions (see picture below left). They also stay close to the mother for the first few hours. And a few cockroaches are actually viviparous, nourishing the hatchlings inside their bodies until they are ready to face the world.

Brooding is the most common form of care. This is common with ovoviparous roaches, in which the newly emerged nymphs cluster around the female for varying amounts of time, generally less than a day. It takes several hours for the neonate's cuticle to harden, so they are particularly vulnerable during this time. Brooding also allows for transfer of gut microflora from a fecal meal provided by the mothers. In some species, the female expels a gelatinous mass that the young nymphs eat. Sometimes the mother even transports the neonates for some time after hatching.

Biparental care is seen in a couple of wood eating cockroaches that nest in rotting logs; the wood is a food source (compare termites). The young may remain with the parents for extended periods of time.

In a few species, young are altricial, hatched blind, delicate and dependent on parental care for one or two instars.

Cockroaches are generally considered good parents in the insect world!

Neonate Gromphadorhina portentosaFemale German cockroach with ootheca

Left, cockroach neonates, photo by Matt Reinbold; right, female German cockroach with ootheca. Supplier: Biopix; both from EOL, the Encyclopedia of Life.

Parental Care

Cockroaches are considered among the most caring parents in the insect world. This care ranges from merely dropping the ootheca in a protected spot, to mothers staying with the neonates for a couple of hours, to both parents caring for the young for several years in a nest, and everything in between.

Gravid females produce oothecae or egg cases. Many, like the German cockroach shown in the right hand image below, simply drop their oothecae in convenient spots such as crevices and other protected areas, though some actively defend them. Some females dig shallow burrows for their oothecae, or even live underground where they and their nymphs are safe. Others, such as Gromphadorhina portentosa, retain their egg cases inside their bodies until the nymphs hatch (ovoviparity). Newly hatched G. portentosa nymphs are also provided with their first meal - the ootheca and accompanying secretions (see picture below left). They also stay close to the mother for the first few hours. And a few cockroaches are actually viviparous, nourishing the hatchlings inside their bodies until they are ready to face the world.

Brooding is the most common form of care. This is common with ovoviparous roaches, in which the newly emerged nymphs cluster around the female for varying amounts of time, generally less than a day. It takes several hours for the neonate's cuticle to harden, so they are particularly vulnerable during this time. Brooding also allows for transfer of gut microflora from a fecal meal provided by the mothers. In some species, the female expels a gelatinous mass that the young nymphs eat. Sometimes the mother even transports the neonates for some time after hatching.

Biparental care is seen in a couple of wood eating cockroaches that nest in rotting logs; the wood is a food source (compare termites). The young may remain with the parents for extended periods of time.

In a few species, young are altricial, hatched blind, delicate and dependent on parental care for one or two instars.

Cockroaches are generally considered good parents in the insect world!

Neonate Gromphadorhina portentosaFemale German cockroach with ootheca

Left, cockroach neonates, photo by Matt Reinbold; right, female German cockroach with ootheca. Supplier: Biopix; both from EOL, the Encyclopedia of Life.