Which one communicates by means of pheromones ?

Options

A. Annelids
B. Gastropods
C. Insects
D. Birds.

Answer

To determine which group communicates by means of pheromones, we can analyze the options provided:

1. **Understanding Pheromones**:
- Pheromones are chemical substances secreted by an organism into the environment. They serve as signals for communication, particularly in mating and social behaviors.

2. **Analyzing the Options**:
- **Annelids**: These are segmented worms (e.g., earthworms) and do not primarily use pheromones for communication. They rely more on physical contact and other forms of signaling.
- **Gastropods**: This class includes snails and slugs. While they do have some chemical communication, they are not known for using pheromones in the same way insects do.
- **Insects**: Insects are well-known for their use of pheromones. They release these chemicals to attract mates, mark territory, or signal alarm. This is a characteristic feature of many insects, making this option likely correct.
- **Birds**: Birds primarily communicate through vocalizations and visual displays rather than pheromones.

3. **Conclusion**:
- Based on the analysis, the correct answer is **insects** (option C), as they are the group that communicates using pheromones.

### Final Answer:
C. Insects