Flea Adult

Last updatedLast updated: July 11, 2022
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Adult Cat Fleas are one of the most important pests of homes, lawns and pets in the United States.  There are other flea species but the Cat Flea is the one most often encountered by pest professionals and individuals who prefer do-it-yourself pest flea control.  There is a very slight chance of encountering other species of fleas but control products and methods are the same with other species as those used in controlling cat fleas.  The only exception to this would be in controlling flea hosts.
Details discussed here will include the flea life cyclelarge and small fleasmale fleas vs. femalesadult flea life expectancyfemale fleasnumber of flea eggs produced by female and other information to use when implementing your flea control and pest prevention program.
The adult flea is one of the four stages of fleas.  Beginning with the flea egg, the life cycle continues through three instars of larval development and into the more dormant pupal stage where the flea larvae are transformed into adult fleas.  The egg, larva, pupa and adult comprises what is known as complete metamorphosis.

Surprisingly, adult fleas make up only a minor portion of the total flea population in an infested area such as inside a home.  Most of the time the eggs and larvae compose about 80% of the fleas in a home.  Understanding all stages of the flea’s life cycle will give you necessary information to use when controlling indoor fleas (and outdoor infestations) and when putting together an integrated pest management (IPM) approach to flea prevention.  Although adult fleas make up only a small percentage of the total flea population in a home, they are the most visible and most irritating by far.  Smart pest control measures first target the immature stages of the insect’s development.  Using pesticides to kill adult fleas is important in many cases but should not be the main target in a professional IPM approach.  Not only are there more immature stages than adults but the adult flea can be more difficult to control than its immature eggs and larvae.

Adult Cat Fleas

This flea information article contains points of interest that mainly concern adult cat fleas.  Both male and female will be discussed but primary attention should be given to female fleas.  A flea is specially designed for its life style, with both body and senses that enables the insect to locate a host, maneuver the body of its host and to feed in a way that supplies its own needs and those of its offspring.
The rear legs of a flea are a wonder in not only what they can do but also how they do their job.  The leg muscles are indeed strong and well coordinated to give the flea maximum jumping power, much as the legs of other jumpers such as grasshoppers and locusts.  The force of the jump causes the flea to tumble in mid-air as it travels upwards and outwards.  Hairs facing to the rear and special claw-like “feet” help the flea catch and hang on to its intended target.
The body of a flea is shaped in a manner that allows ease of movement through the fur or its host.  It is thinner or flatter than most insects and equipped with body hair that has a two-fold purpose: sticking to its host and moving around on its host.  With its shape and body hair, the flea’s body is likened to a Velcro dart.  Responding to movement, vibrations and the warmth, carbon dioxide and humidity of an animal’s breath and body, the flea jumps upwards towards its intended target.  Once it touches the target (animal) it is able to make a safe landing with the aid of body hairs that only point backwards.  These backwards facing hairs give the flea the Velcro effect needed to stick to its host and to crawl forward without falling back to the ground.  Even the hairs that resemble a tiny beard serve as extra support, especially during feeding.  This beard-like array (called a comb) is one of the characteristics that distinguish the Cat Flea from other fleas.
Once its host has been located and the flea has managed to land on its host, it begins to bite and feed.  A single flea can bite an animal numerous times per hour, searching for a suitable area of skin for feeding.  The flea’s mouthpart is known is designed for piercing skin and siphoning blood for a meal.  If animal’s could immediately detect the flea’s bite, the animal would respond before the flea could feed.  To prevent this, the flea saliva desensitizes the area long enough for the insect to have its blood meal.  This saliva also causes an allergic reaction in many animals, causing them to itch and scratch.

Special Flea Characteristics

  • Locate suitable host by detecting movement, vibrations, animal breath (warmth, humidity, carbon dioxide,) body heat.
  • Incredible jumping power that gives them the ability to reach their host.
  • Body hair that helps staying on and moving through the hair of animals.
  • Saliva that prevents immediate detection of its feeding.
  • Mouthparts and special hairs that maximize feeding.
  • Ability to drink enough blood to sustain life of itself and its future larvae.
  • Fecal material (blood) dries quickly so as not to stick to animal but to fall off.
  • Tiny eggs that easily drop off of animal and land in same area as fecal material.
  • Blind, legless larvae can locate fecal material needed as food source.
  • Larvae saliva helps bind together materials which make up structure of water-tight, camouflaged pupal casing.
  • Completely developed adult flea can remain in pupal casing for over a year, waiting for signals of suitable host.

If your cat or dog scratches, it does not always indicate fleas.  When the pet constantly chews or bites its feet, the pet could be showing indications of an allergy.  Not all scratching is caused by fleas.  Not all allergic reactions are caused by flea allergies.  If a cat or dog is allergic to flea saliva, they can have an allergic reaction for one or two weeks after being bitten by a flea.
There is no such thing as a baby flea, just as there are no baby flies.  (Small flies are different species than larger flies.)  When the flea emerges from its pupa, it is as large as it will ever be.  The size difference we see is due to blood consumed during feeding, which makes the flea swell to a larger size.  The enormous amount of blood consumed by a flea is far more than its body requires.  When viewed with a high powered microscope, the flea can be observed feeding for long periods.  As it feeds, small drops of undigested blood are passed through the digestive tract.  As these drops emerge they quickly harden and drop from the flea.  The excess blood is used to feed the next generation that emerges from the developed eggs: flea larvae.  Since eggs and coagulated blood both fall in the same area, larvae that emerge from flea eggs do not have to travel far to find their food.
Important information for inspection: adults prefer to stay on their host; eggs and hardened blood drops are laid on the host but easily fall off; larvae are not very mobile.  This means a great deal when inspecting a home for flea hot spots.
Size difference in visible indoor fleas is important when evaluating the progress of your flea control program.  It is normal to see small, newly hatched fleas in a home that has been treated for flea control.  The fleas continuously “hatch” due to the large number of pupae in the area.  When larger fleas are seen in a treated area, 7 to 10 days after initial treatment, it tells us that something is wrong.  Larger sized fleas in a treated area tells us that either indoor hot spots have been overlooked or that fleas are being transferred from an exterior source.  (Exterior sources can include a flea infested lawn, cats that have indoor and outdoor access, introduction by a new or visiting pet, rodent problems, etc.)
Newly hatched adult fleas usually jump higher and faster because they are very hungry.  The nutrients stored by the third instar larvae are used up during the transformation that takes place in the pupal stage.  This explains why persons moving into a new home or returning home from a vacation are attacked by fleas in such a fierce manner – the fleas are hungry!  When plague infested rats were attacked by fleas, a frightening side effect was discovered: fleas that had contracted the plague had trouble swallowing.  They (the fleas) could jump and bite all they wanted but they could not get a satisfying meal.  As they got more desperate for food, they jumped frantically from host to host.  It was in this manner that the plague spread quickly and killed millions of people in Europe:  from rat to fleas to people.
Generally, the male adults emerge from their cocoons (pupal casing) shortly before the adult female fleas.  The males may emerge before the females but female fleas far outnumber male fleas.
There have been numerous studies citing how long the adult flea can live, with varying opinions on the life expectancy of the flea.  Variables include whether or not the flea host was allowed to groom, food availability, temperature and humidity of the surroundings.  Without a food source (when adult fleas emerge in an area where there are no warm blooded nesting animals) the fleas might die as soon as a week.  With a suitable food source, the adult flea can live for several months.  Opinions vary but you can narrow the life span down to an average of two months with a seven month life span being on the high end.  However, the longevity of the adult flea is not nearly as important (from a flea pest control perspective) as the hardiness of the flea pupae.

Both adult and larval stages of the flea require warm blood.  The larvae will feed on different organic debris but require blood for proper development.  Larvae find blood in the form of dried fecal matter from adult fleas, which is made up almost entirely of undigested blood.
The adult flea, however, must have blood that it extracts from its host.  The blood source must be from a living, warm blooded nesting animal.  Fleas are not creatures which readily feed on a dead animal.  If its host dies, the flea will detect the drop on blood temperature and desert its host in search of another suitable host.   Without sufficient amounts of foods, the adult flea cannot survive and the female cannot lay her eggs.

Female Flea

As noted above, male fleas emerge before the females yet the females far outnumber the males in the population.  After emerging from her pupal stage the female flea must immediately locate her host and then feed.  Once she has had her first blood meal the flea then mates and begins her major job: laying eggs and providing enough food for larvae that will be emerging.  Just her initial mating is all that is needed for normal output but she will need numerous matings to produce the extremely high number of eggs (over 800 eggs in her lifetime) that have been seen in laboratory tests.
Studies vary on the exact number of eggs that the female is capable of laying each day of her life but you can expect for her to lay a few eggs every day.  Maximum number of eggs produced may reach as high as 35 to 40 eggs per day.  This maximum number is only achieved when its host cannot groom itself and other conditions (food availability, heat and relative humidity of her environment) are at their best.
The female flea must have a blood meal before she mates and begins to lay eggs.  Usually the first batch of eggs appear about two days after the initial feeding and mating.  As previously mentioned, the female lays several eggs each day of her adult life but the peak period is about 1 week after egg production begins, tapering off to a few eggs each day.  In her lifetime, the female will lay over 200 eggs and is capable of laying over 400 eggs before her demise.  Higher numbers have been noted in pristine, laboratory conditions where heat and humidity are tightly controlled and the host animal is not allowed to groom.

Fleas prefer to spend their entire adult life on their host but obviously are shaken loose during the activities of the host animal (jumping, running, scratching, grooming.)  Inspection and vacuuming of a home should always be thorough.  Hotspots that often require extra attention are usually where pets frequent.  Adult fleas, flea eggs and future food for larvae all fall off of the host in the same general area.  Being sensitive to light, the larvae are usually close by but underneath or behind objects.
Put your knowledge of the adult flea habits and the complete flea life cycle as the major tool in flea management.

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