Cockroach Spit

Caution: The following article is about whether cockroaches are spitting or vomiting. You may wish to proceed with caution.

If you have ever visited Pacific Science Center’s Insect Village, you may have had an opportunity to handle a Madagascar Hissing Cockroach (Gromphadorhina portentosa). Many people have learned a new appreciation for insects from this contact. Some have overcome longstanding fear of bugs. But few know that the cockroaches have to learn not to fear us, too.



While many legends exist about the ability of cockroaches to survive nuclear disaster, microwave ovens, and other dire fates, the experience of our Life Sciences staff has been that these insects are not invulnerable. They enjoy being treated well and show signs of stress when times get tough, just like any other animal.


Roaches show stress in several ways. Most commonly they hiss (hence their common name) the first few times we handle them, before learning we are safe. We also look for loss of muscle tone, and fighting as signs that the animals need more rest and less work.

But there is another sign of stress that has been observed recently, that got us concerned. A couple of people have seen our roaches emitting bubbles of clear liquid from their mouths during handling. Life Sciences manager Sarah Moore had seen this behavior before. It happened once while treating the roaches for mites, something they really hate. It occasionally happens when a roach is accidentally dropped, or when brand new animals are introduced. But it has been uncommon, and when it happens it is of note.


The usual modes of inquiry turned up very little information about this phenomenon, but we did learn this: The liquid is not vomit, but saliva, which roaches produce in large amounts to help mobilize and digest food. German and American roaches are known to use pheromones in their saliva to attract others of their species and also to communicate danger. Depending on the pheromone, other roaches will either approach or flee from this secretion. It is possible that our roaches are doing the same thing.

At any rate, it was clear that the insect doing this was unhappy, and he was moved out of the handling schedule. We are training staff to report this behavior, which we hope will be as rare in the future as it has been up till now.


Photographer’s note: The clear liquid in the photographs is water. No cockroaches were harmed in the making of this story.