Difference Between Fleas and Gnats


Main Difference

The main difference between the Fleas and Gnats is that Fleas are small insects with eyespots belongs to order Siphonaptera, whereas Gnats are flying insects with compound eyes belongs to order Dipterid.

Fleas vs. Gnats

Fleas belong to the Siphonaptera order of Animalia kingdom, while gnats belong to the Dipterid order. Fleas are small insects that are non-fliers; on the other hand, gnats are delicate insects that can fly, contains one pair of wings. The body of fleas is about 1.5 to 3.3mm long, whereas gnats are about 1 to 15mm in length. Fleas have simple eyespots, or some have no eyes; on the other side, gnats have compound eyes.


Fleas are without wings with the modified legs for high jumping; on the flip side of the coin, gnats have wings have pair of wings for flying. Fleas have a tough and hard body as covered with sclerites, whereas gnats have a small and delicate body with slender legs. Adult fleas suck the blood of the host body as they are parasites by proboscis, while gnats can feed the plants, fungi, and even can feed the blood.

Fleas larvae feed by their specialized apparatus as they can feed on their adult feces; on the other hand, gnats larvae feed on plants as they are considered as the carnivores. Fleas lay oval-like, small eggs, white-colored; on the other side, gnats lay eggs on the terrestrial and aquatic environment. Fleas cause itching, raised spots as parasites on the host, while gnats also irritate the host body. Fleas suck the host blood for feeding purposes, whereas gnats do not specifically suck the blood as female members of some species suck blood for egg development.


Comparison Chart

Fleas are tiny insects, having eyespots, long legs belong to order Siphoneptera as wingless insects.Gnats are insects with the slender and delicate body, have compound eyes, belongs to order dipterid as winged insects.
1.5 to 3.3mm1 to 15mm
Flying Ability
Cannot fly as WinglessCan fly as have pair of wings
Feeds blood as parasitesFeeds on plants, fungi, insects, and blood
Eyes Feature
Simple eyespots or some species with no eyesCompound eyes
Small insects, tough bodies, flattened sideways, composed of sclerites.Small, delicate insects have long legs.
Life Span
2 to 3 months2 to more than two weeks

What are the Fleas?

Fleas are the small insects that belong to the order Siphonaptera that live as the external parasite on the bodies of mammals and birds. They are called parasites instead of any symbiotic relationship because they suck the blood of the host animal by the proboscis (elongated appendage). Fleas are so small that they have a size of 1.5 to 3.3mm length with brown color having flattened sideways and narrow bodies. Fleas legs are modified at the end to form the claws which grasp the host surface. Fleas can jump 50 times than their body length allow.

They have simple eyespots that aid the vision by a simple biconvex lens instead of compound eyes. The life cycle of fleas has four common stages, which account for the population of the fleas as 50% eggs, 35% larvae, 10% pupae, and 5% adults. Larvae also feed by the specialized feeding apparatus as their primary food is the feces of adult fleas.

In the adult stage, they primarily keep on sucking the blood and start reproducing. The adult life span is only 2 to 3 months, but in ideal conditions of survival, they can live up to a year. They feed on the warm-blooded host. On the host, they cause an itching sensation, raised swollen epidermis after excessive biting, can cause secondary hair loss, and even anemia in severe cases. Their body is hard and tough that they can withstand the scratching of the host to eliminate them.

Fleas served as the vectors of the diseases, such as bacterial, viral, and rickettsial diseases.

What are Gnats?

Gnats are flying insects belong to the order Dipterid with suborder Nematocera. They can include biting as well as non-biting species. Gnats have compound eyes, six legs, and three body parts include the abdomen, thorax, and head. They have a length of about 1 to 15mm and contains one pair of wings, but some of their species are weak fliers. They feed on the plants, fungi, insects, and sucks the blood as parasites. Gnats can serve as the source of pollination as pollinators by feeding on the crop pests that include aphids and gnats commonly.

The blood-feeding species of gnats are very small as only the female members of the species feed on the blood for the development of their eggs, whereas the male members of species feed on the plants. For the mating, the male gnats assemble in the large swarms. Non-biting gnats are aquatic, and some are free-living as some of which called carnivores as they feed on the plant.

Gnats usually fly in the form of “clouds” as large groups. Their larvae may be mobile or immobile, as they can be aquatic or terrestrial. Adults can survive for a week or more than two weeks as a female can lay up to 1000 eggs in their lifespan. Gnats bite can cause the swollen, redness, itchiness, as well as through biting, they can serve as vectors of diseases for animals.

Non-biting gnats do not cause harm to plants, whereas the presence of a large number of larvae can damage by stunting the growth of plants and root damage.

Key Differences

  1. Fleas belong to the order Siphonaptera of the Animalia kingdom, whereas gnats belong to the Dipterid order.
  2. Fleas are non-flying without wings can jump more than their body length, while gnats are flying insects have a pair of wings.
  3. Fleas have a tough body that is composed of sclerites; on the other hand, gnats have delicate and slender bodies.
  4. Fleas have simple eyespots; on the flip side of the coin, gnats have modified compound eyes.
  5. Fleas have about 1.5 to 3.3mm length, whereas gnat’s body is about 1 to 15mm long.
  6. Fleas feed on the blood of the host as a parasite, while gnats on the basis of species feed on the plants, fungi, insects, and blood as well.
  7. Fleas larvae have specialized feeding apparatus as they feed on the adult feces; on the other side, gnats larvae are considered as the carnivores as they feed on the plants.
  8. Fleas lay oval-like, small eggs on their host, while gnats lay eggs in the terrestrial and aquatic environment.
  9. Fleas lifespan is about 2 to 3 months; on the other hand, gnat’s lifespan can be about more than two weeks.


Fleas are small insects that belong to the order Siphonaptera, with long legs modified to claws, parasites as feed on blood, while Gnats belong to order Dipterid with compound eyes with various feeding sources.

Aimie Carlson

Aimie Carlson is an English language enthusiast who loves writing and has a master degree in English literature. Follow her on Twitter at @AimieCarlson