When a grasshopper is picked up or disturbed, it often responds by expelling a dark, brownish liquid from its mouth. This common phenomenon, sometimes colloquially referred to as “tobacco juice” due to its color and consistency, is a reflexive action triggered by stress or pressure. The expelled substance is not true saliva, but rather a protective measure that serves to deter a potential threat.
The Composition of the Regurgitant
The dark material that a grasshopper expels is technically a regurgitant, consisting of contents drawn directly from the foregut, which functions as a temporary storage area known as the crop. This fluid is primarily composed of partially digested plant matter, which is the source of the substance’s characteristic dark, viscous appearance. Mixed into this plant material are various digestive enzymes that the insect uses to break down its food.
The specific color and consistency of the regurgitant can vary slightly depending on the grasshopper’s recent diet, reflecting the chlorophyll and breakdown products of the plants it consumed. Releasing the contents of the foregut is a rapid, involuntary response initiated by the insect’s nervous system when it detects pressure on its body.
Defensive Behavior and Purpose
This act of expelling crop fluid is a non-toxic defense mechanism known as defensive regurgitation. The primary purpose is to make the grasshopper instantly unappetizing to a predator, encouraging the attacker to release its grip. It works through two main deterrent effects: chemical aversion and a startle response.
The chemical aversion is often the most effective part of the defense, as the regurgitant is typically bitter and noxious. For grasshoppers that feed on plants containing specific defensive chemicals, the regurgitant can incorporate these concentrated plant secondary compounds, making the substance distasteful or even mildly toxic to small predators. Studies have shown that the effectiveness of the deterrent is directly related to the specific type of plant the grasshopper has recently eaten.
For a small predator, such as a lizard or bird, the sudden coating of a dark, foul-tasting fluid on their mouthparts can be startling and repulsive, prompting them to drop the insect immediately. This momentary distraction allows the grasshopper a chance to escape its predicament. The behavior is a last-resort measure when the grasshopper’s primary defense, which is simply jumping away, has failed.
Safety and Human Interaction
For humans, the grasshopper regurgitant is generally considered harmless and poses no significant health risk. The fluid is not venomous, and the insect is not known to carry diseases that can be transmitted through this defensive action. Although some sources describe the fluid as acidic or having a bad smell, it is not corrosive to human skin.
The main practical concern for people handling a grasshopper is the potential for temporary staining on the skin or clothing. This is due to the partially digested plant matter and chlorophyll pigments within the fluid. If the liquid does come into contact with skin, it can be easily washed off with soap and water. There is also a minor risk of irritation if the substance were to get into a person’s eyes or an open cut, but this is easily managed with flushing the area.