May 21, 2012 – One Organ, Different Uses
QUESTION:
What is the cockroach cerci?
ANSWER:
Cerci is actually plural for the pair of devices sticking out the back end of the abdomen on many insects, and singular is "cercus". In cockroaches they are the pair of small and pointed appendages that the roaches use as sensory devices, sensing the slightest air movement on them that might signal an enemy is near, and triggering the muscles of the legs to take immediate flight to escape. On earwigs the cerci are the "pincers" at the back end, and these are used by these insects to capture prey that they eat or to defend themselves with a pinch. On male earwigs the cerci tend to be curved and long, with teeth at the base, while the cerci of the females are untoothed and more parallel along their length.
View past Ask Mr. Pest Control questions.
What is the cockroach cerci?
ANSWER:
Cerci is actually plural for the pair of devices sticking out the back end of the abdomen on many insects, and singular is "cercus". In cockroaches they are the pair of small and pointed appendages that the roaches use as sensory devices, sensing the slightest air movement on them that might signal an enemy is near, and triggering the muscles of the legs to take immediate flight to escape. On earwigs the cerci are the "pincers" at the back end, and these are used by these insects to capture prey that they eat or to defend themselves with a pinch. On male earwigs the cerci tend to be curved and long, with teeth at the base, while the cerci of the females are untoothed and more parallel along their length.
Cerci are present on most other Orthopterans, which is the group that includes grasshoppers and crickets, and these also may be elongated, narrow appendages sticking out the back. On grasshoppers they actually have sound receptors in the cerci, although most of the reception of the chirping by male crickets is detected by a tympanum on the front legs. Because of that distinct difference in the shapes of the male and female cerci in earwigs, as well as in some crickets, it is suggested that these devices must also play a role during mating.
So, in cockroaches the cerci are important defensive devices that signal the possible presence of predators. This is one reason they immediately run when we enter their area, as our movement of the opening of a door causes the tiny air movement that their cerci detect.
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