A siphon is a tubular organ of the respiratory system of some insects that spend a significant amount of their time underwater, that serves as a breathing tube. The larvae of several kinds of insects, including

mosquito Mosquitoes, the Culicidae, are a Family (biology), family of small Diptera, flies consisting of 3,600 species. The word ''mosquito'' (formed by ''Musca (fly), mosca'' and diminutive ''-ito'') is Spanish and Portuguese for ''little fly''. Mos ...

es, tabanid flies, and Belostomatidae, live in the water and breathe through a siphon. Some adult insects which spend considerable time underwater have an abdominal breathing tube. For example, adult

water scorpion Nepidae is a family of exclusively aquatic Heteropteran insects in the order Hemiptera. They are commonly called water scorpions for their superficial resemblance to scorpions, due to their raptorial forelegs and the presence of a long slender p ...

s have the caudal

process A process is a series or set of activities that interact to produce a result; it may occur once-only or be recurrent or periodic. Things called a process include: Business and management * Business process, activities that produce a specific s ...

which consists of a pair of half-tubes capable of being locked together to form a siphon by means of which air is conducted to the

trachea The trachea (: tracheae or tracheas), also known as the windpipe, is a cartilaginous tube that connects the larynx to the bronchi of the lungs, allowing the passage of air, and so is present in almost all animals' lungs. The trachea extends from ...

e at the apex of the

abdomen The abdomen (colloquially called the gut, belly, tummy, midriff, tucky, or stomach) is the front part of the torso between the thorax (chest) and pelvis in humans and in other vertebrates. The area occupied by the abdomen is called the abdominal ...

when the tip of the tube is thrust above the surface of the water. In immature forms the siphon is undeveloped and breathing takes place through abdominal spiracles.

References

Insect anatomy Invertebrate respiratory system {{insect-anatomy-stub