How do fleas move?

Summary

Fleas use their prodigious jumping feats to contact hosts passing in their
vicinity.Aflea in the correct physiological state is triggered to jump by hostrelated
stimuli. The jump is aimed towards the source of the stimuli, and
the legs, especially the middle pair, are held out ready to grasp onto a host
if the jump is successful. The success of fleas is a testimony to the efficiency
of this means of moving onto a host. Jumping seems to combine the
ability to move rapidly, normally restricted to flying insects, with the capacity
to do away with wings, which are such a hindrance to movement within
the host’s covering. Jumping is also compatible with the production of a
flattened body, which further enhances the insect’s mobility on the host,
but the mechanism is clearly not as efficient as flight in host location as we
can see from the distribution of fleas. Fleas are mainly limited to hosts that
rear their young in some sort of nest, and so fleas are generally not found on
grazing and browsing animals (biology of blood sucking)

Shortly after emerging from the cocoon, the flea
begins looking for a blood meal. Visual and thermal
cues appear to be responsible for stimulating C. felis
felis to jump onto a bost. newly emerged adult cat flea residing in the carpet
will move on top of the carpet canopy where it will
be able to jump onto a passing host [Biology of the cat flea]

In normal conditions, when fleas are in the hair of a dog or a cat, they walk. Jumping is
usually performed by young imagos to catch the host and by adult fleas to leave it when they are disturbed or when the animal temperature decreases during anaesthesia or after the host’s
death (Franc, 1998). (comparison of jump)

the laterally compressed body, high and narrow head capsule and flexible joints
of the thorax and abdomen of fleas allow them to move through host pelage by
dividing the hair during forward movement. The flea thorax consists of three separate modified segments (pro-, meso- and
metathorax), whereas the abdomen consists of 10 segments. The posterior margins
of each segment form collars that overlie the anterior margins of the next
segment. As a result, these segments are able to ‘squeeze’ into each other. In
contrast to most winged insects, separation of the mesothorax and metathorax
in fleas leads to the absence of a pterothorax which is characteristic of other
holometabolous insects. It has been suggested that flea ancestors also did not
possess a pterothorax (Medvedev, 2003a, 2005). This lack could be considered as a
pre-adaptation to ectoparasitism on fur-covered hosts (see Chapter 4). Separation of the thoracic segments, possession of movable between-thoracic sclerites and
highly developed phragmata are features that allow high flexibility of the flea
body. In contrast to other Holometabola, the flea prothorax is not reduced but is
tightly connected with the head. The lower part of the prothorax (pleurosternum)
is strongly elongated, exceeding at least two times the length of the
pronotum. The pleurosternum protrudes anterior to the notum and envelops
the posterior part of the head from beneath. As a result, the head and prothorax
together constitute a frontal complex which is movable relative to other
thoracic segments (Medvedev, 2003a, b). Structures of this complex also include
maxillary plates (first segments of the maxilla that possess highly developed collars)
and fore coxae. Due to an elongated pleurosternum, fore coxae are situated
anterior to the notum. The maxillary plates are broad in the middle, but narrow
at the bases and apices. As a result, the anterior frontal complex of a flea is
shaped like a keel which divides the host’s hairs or feathers or particles of the
substrate of its burrow/nest during flea movement. In addition, the frontal and
occipital regions of some fleas are covered with basiconic sensilla and large numbers
of pores (Amrine & Lewis, 1978; de Albuquerque Cardoso & Linardi, 2006).
These pores are openings for the epidermal glands and exude oily substances
onto the cuticular surface of a flea facilitating movements among the host hairs
(Rothschild & Hinton, 1968; but see Smith & Clay, 1985 and de Albuquerque
Cardoso & Linardi, 2006).(functional and evolutionary)

Jumping allows these wingless blood-sucking insects to attack their
hosts successfully, although their major type of locomotion remains walking
(Marshall, 1981a). Therefore, the daily metabolic cost of flea jumping can be relatively high, being
in between that of flight and that of energetically less demanding locomotory
modes such as walking or running.(functional and evolutionary)

Fleas are able not only to move through dense host pelage, but also to
jump, to move through the substrate of a host’s burrow or nest and to move on
vertical surfaces. The diversity of modes of flea locomotion and their efficiency
using these modes for host location and exploitation suggest that these locomotory
patterns were most likely naturally selected as means to guarantee an
evolutionary success of the way of life of the obligatory periodic burrow/nest
parasites of avian and mammalian hosts. (functional and evolutionary)

Fleas have evolved distinctive morphological characteristics,
particularly elaborate spines and setae (Traub 1972), to reduce the effectiveness of host
grooming. Structures such as the ctenidia permit the
ectoparasite to anchor itself within host pelage or
plumage and to resist the host’s grooming efforts
(Humphries 1967). Studies have demonstrated that
anatomical features such as helmets, ctenidia, head
shape, and even modifications of shape and size of
spines and setae can be correlated with particular
characteristics of the host’s coat (Traub 1985). Thus
fleas are particularly adapted morphologically to
thw~ grooming efforts of their hosts. (host grooming)

However,
the cat ßea is a species that has extensive spination and
is very successful in remaining on a cat throughout
coevolution. The cat ßea may be very adapted to the
catÕs body and also successful in avoiding grooming,
the most intensive selection pressure. Thus, it is worthwhile
exploring other possible factors, such as ßea
pheromone or the skin temperature of various areas on
the cat, involvedin the movement of ßeas on the host
animal. (distribution on cats)

Adult fleas are strongly sclerotized, and ca. 2–10 mm in
length. They have thin, flattened bodies and backward-directed
spines on their legs and bodies that facilitate forward movement
through fur, hair, or feathers and prevent them from being easily
dislodged (Figure 1). (fleas and flea borne diseases)

The body is laterally compressed, which allows for easy movement through fur, and the hind legs are highly developed, powerful for jumping. (use of mathematical)

Once stimulated, the imago tears open the cocoon, probably as
a consequence of its agitated movements, and jumps onto the
fi rst mobile, warm “object”, usually an animal. (flea control in flea allergic)

Flea movement can be slowed with refrigeration. (prevalence central london)

In addition, boreids have the ability to jump in a manner
that appears similar to that of fleas, although detailed
morphological and functional comparisons have yet to
be performed. Boreids emerge as adults only during
winter months, are closely associated with mosses, and
like many other winter insects, the reduction and loss of
wings reduces the body surface area, and may be an
adaptation to the cold. The ability of boreids to jump
facilitates movement on soft, fluffy snow, and is also
probably an adaptation to this extreme environment.
When the boreid–flea ancestor shifted from a snowy,
mossy habitat to the nest of a mammal host, it had
already undergone the loss of wings and acquired the
ability to jump. Subsequent modifications to the primitive
flea include lateral flattening, the development of
sucking mouthparts, and the development of the elaborate
combs and setae as further adaptations for a
parasitic life. If the pterosaur scenario is correct, then
one must postulate the less-likely shift from a boreid-like
ancestor to the pterosaur, and from the pterosaur to
mammal hosts. That would have been a remarkable
jump indeed. (molecular phylogeny)

Bristles, sensilla chaetica, are large, strongly
fluted sensilla. In some regions bristles appear
intermediate in structure between hair sensilla
and true bristles, as on the maxillary palp
(Figs. 24, 26). Most bristles have longitudinal
flutings that parallel or spiral the length of
the axis of the shaft (Fig. 3). Most of the
bristles probably provide tactile informatioln
to the flea regarding contact with hair and
other structures in the environment. Many of
the longer, exposed bristles probably function
to fend off hair from the cuticular surface during forward movement and serve to help
anchor the flea in the hair during scratching,
biting, etc., by the host.
The genal ctenidia may be homologous to
bristles. According to Traub (1968), studies
on comb development show that each ctenidium
is derived from a single epidermal cell
and is thus homologous to other sensilla. The
function of combs, as stated by Humphries
(1966), is to keep the flea on the host by
anchoring or snagging onto hair. (the topography)

The adult Ctenocephalides displays little tendency to leave its dog or cat host unless the population approaches about 200. Then a few fleas may get off occasionally, especially when their host comes in contact with another, possibly less parasitized individual. A common misconception exists that Ctenocephalides fleas constantly jump on and off their hosts and find new hosts in this manner. In fact, most of the fleas a dog or cat acquires are brand new ones straight out of their pupal cases (Georgis)

Morphologically, adult fleas are unique and
unlikely to be confused with other types of insects
(Fig. 7.1). Many of the most distinctive features of fleas
are related to their ectoparasitic lifestyle and bloodfeeding
habits, including the lack of wings, laterally
compressed body, and modifications of the hind legs
and metathorax for jumping. The various setae, spines, and combs found on fleas
are thought to help fleas move efficiently through the
host’s pelage or plumage, prevent dislodgement from
the host, steady the flea during feeding, and perhaps
provide some protection against being crushed. Setae
and spines appear on many regions of the flea’s body,
while combs are usually located on the first thoracic
segment (pronotal combs) and/or the side of the head
(genal combs). Combs occur less often on the front of
the head, as in the helmet fleas (Stephanocircidae),
or on the first abdominal segment, as in the genus
Stenoponia, which also has pronotal and genal combs
(Figs. 7.5A, B).
The arrangement and characteristics of the setae,
spines, and combs often correspond to the characteristics
of their hosts’ pelage or plumage. For example,
spiny hosts, such as hedgehogs, porcupines, and
echidnas, are hosts to a few highly specialized fleas
that exhibit heavy, widely spaced comb spines. The
fleas found on each of these hosts are not closely
related to those found on the other two types of
mammals, and it appears that the similar appearance
of their comb spines represents a case of convergent
evolution. Other hosts, such as rodents, have less
coarse pelages, and their fleas typically have comb
spines that are finer and more numerous.(biology of disease)

Adult fl eas are about
1– 4 mm in length and are strongly fl attened from side to side. They
are equipped with relatively long legs armed with strong outwardly
projecting spines. Cat fl eas have a collar of spines (ctenidium) on the
back and another row of spines above the mouth. These characteristics
allow for rapid movement through the host’s hairs and also serve
to resist removal from the fur. (encyclopedia of insects)

Details

References