Human Flea, Pulex irritans, female (Fig. 29)
From the Greek siphon = a tube, and aptera = without wings.
Fleas are small wingless insects, as adults, laterally flattened, blood-sucking and capable of jumping. The body has numerous setae, is shiny and yellowish brown to black in colour. The head has short antennae that lie in deep grooves, and can be raised and used for grasping the female during mating. The mouthparts are adapted for piercing and sucking and consist of three elongated, sharp piercing elements. Eyes may be present or absent, but ocelli are always absent. Genal and or thoracic combs may be present or absent. The legs are rather long and stout, adapted for clinging with large coxae, and long 5-segmented tarsi. The hind legs are especially important for jumping.
Segment X on the abdomen in both sexes bears a dorsal sensillum, which is rather like a pincushion in appearance. Cerci are absent. The female may have one or two spermatheca, and the male genitalia are the most complex in the entire animal kingdom.
The life cycle consists of egg, larva pupa and adult, with the pupa in a cocoon. Eggs laid by the female fall free from the host, usually accumulating in the nest, den or home of the host. The larvae, which are rather elongate, whitish and rather maggot-like, lacking both eyes and legs, but normally rather setose, feed on the organic debris and faecal droppings of the parents that collect in dens, nests and the like. There are three larval instars. Pupation takes place in a cocoon, and the newly formed adults can remain for many months in this cocoon without food. Such pre-emergence adults are sensitive to both warmth and vibration, and can emerge quickly to infect the host or any other warm-blooded animal causing a disturbance. This phenomenon is well known to many cat-loving owners when they return to a cottage or home after a winter or vacation.
It is only the adult flea that sucks blood from warm-blooded vertebrates. Most fleas are host specific, or restricted to a particular family or Order of birds or mammals. In some species, the breeding cycle of the flea is very closely linked to that of the host. For example, it has been shown that the hormones that circulate within a pregnant rabbit also induce ovary maturation in rabbit fleas.
Most fleas regularly move from one host to another. They are capable of serving as vectors of a number of microorganisms. The best known disease transmitted by fleas is plague, and infectious disease caused by the bacillus Pasteurella pestis (Lehman and Neumann). Endemic typhus caused by a Rickettsia can also be spread to people from rats by fleas. Fleas can also serve as intermediate hosts of tapeworms, such as the tapeworm of dogs and cats.
Of the eight families of fleas known from North America, only seven occur in Canada and British Columbia. The family Rhopalopsyllidae is absent.
Key to families
|Outer internal ridge of middle coxae absent; mesonotum lacking pseudosetae under the collar; metanotum and abdominal terga lacking marginal spinelets; spiracles circular; abdominal terga II-VII with at most one row of bristles; sensillium with 8 or 14 pits per side; hind tibia lacking an outer apical tooth
|Outer internal ridge of middle coxae usually present; apical tooth on hind tibia present and pointed; sensillium usually with 16 or more pits per side
|Combs, spinelets, antepygidiae bristles, spiniform bristles on inner surface of hind coxae, and anal stylet of female all absent
|Some or all of these structures present
|Metanotum lacking marginal spinelets; female sensillum usually more or less convex; anal stylet usually with a long apical bristle or 1 or 2 small to minute subapical ones
|Metanotum with marginal spinelets; dorsal surface of sensillum straight; anal stylet of female with 1 or 2 long lateral bristles in addition to apical one
|Antennal club of male usually extending onto prosternosoma; female with two spermatheca
|Antennal club of male not usually extending onto prosternosoma; female with one spermatheca
|Head with a complete transverse interantennal groove connecting antennal fossae and dividing frons from occiput; genal comb composed of two broad spines which may be pointed or obtuse, arising immediately behind oval angle
|Combination of characters not as above
|Genal comb present or absent; arch of tentorium present and usually clearly visible; interantennal suture variable; eye often sinuate or vestigial
|Genal comb absent; without arch of tentorium in front of eye; interantennal suture absent; eye circular or vestigial
Description of Families
Fleas with no tentorial rod in front of eye, but with three setae present in the ocular row, the uppermost one inserted in front of the eye. The head lacks a genal comb, but is always entire with no trace of an interantennal suture. The club of the antenna in the male extends onto the prosternosoma. A pronotal comb is present. The metanotum and some of the abdominal terga have apical spinelets, and terga II-VII have two or more rows of setae. The sensillum has more than 14 pits on a side. The hind coxae are without spiniforms. Sternum VIII is narrow or vestigial in the male, and sternum IX has an apodemal rod or tendon. A single spermatheca is present in females.
Worldwide there are some 68 genera and 760 species and subspecies. So far 24 genera and 132 species are reported in North America. Twenty genera occur in Canada, and 18 of these are found in British Columbia. To date, 73 species are recorded from Canada, with 42 of these known from the province. Most species live on small rodents, but a few are ectoparasites of birds.
Ceratophyllus vision Baker is the common flea of the Red Squirrel (Tamiasciurus hudsonicus (Erxleben)) east of the Coast Mountains, while C. ciliatus Baker is an ectoparasite of Townsend's Chipmunk (Tamias townsendii Backman), Douglas' Squirrel (Tamiasciurus douglasii (Backman)) and other rodents on the Pacific Coast, including Vancouver Island.
Dasypsyllus perpinnatus (Baker) which has more than 24 spines in the pronotal comb, is the common flea in the nest of numerous birds, especially Passeriformes, west of the Coast Range and on offshore islands.
Foxella ignothus (Baker) is common on the Northern Pocket Gopher (Thomomys talpoides (Richardson)).
Malaraeus telchinum (Rothschild) is a small flea common on the Deer Mouse (Peromyscus maniculatus (Wagner)) on the Queen Charlotte Islands, Vancouver Island and the southern half of British Columbia. Thrassis acamantis (Rothschild) is the common flea on the Yellow-bellied Marmot (Marmota flaviventris (Audubon & Backman) throughout its range in the Interior Dry Belt.
The interantennal suture is usually present, but the anterior branch of the tentorium is present or absent. The antennal fossa is open ventrally, but the club does not often extend onto the prosternosoma. Genal and pronotal combs are usually present. The ventral margin of the pronotum in bilobed or straight. The hind coxae lack spiniform setae on the inner side, and the hind tibia has an apical tooth on the outside. The male sensillum is strongly convex or has a posterior collar. There is one spermatheca in the female.
Worldwide there are 41 genera and 630 species and subspecies. To date, 22 genera and 114 species are reported in North America. So far 20 genera and 50 species are recorded in Canada, with 13 genera and 35 species known from British Columbia. Species occur mostly on rodents.
The genus Epitedia has a frontal tubercle, E. wenmanni (Rothschild) being quite common on voles (Clethrionomys spp., Microtus spp. ) and mice (Peromyscus spp.) across the province. In the genus Corypsylla which has apical spinelets on the anterior abdominal terga, C. ornatus Fox recognized by the apically asymmetrical third spine in the genal comb, is associated with moles in the genus Scapanus in the extreme southwest of British Columbia.
Fleas with interantennnal suture well developed. The antennal club of the male often extending onto the prosternosoma. A genal and pronotal comb is present. The pronotum has at least two rows of setae, and its ventral margin is usually bilobed. The hind coxae lack spiniform setae on the inner side, but the hind tibia have an apical tooth on the outside. Several terga have spinelets or ctenidia. The male sensillum has a posterior collar. The female sensillum is slightly convex dorsally, and females have two spermatheca.
Worldwide there are six genera and 42 species and subspecies. Two genera occur in the United States, Canada and British Columbia, with ten species known from North America, seven species recorded in Canada, and five of these in British Columbia.
Atyphloceras multidentatus (Fox) occurs on the Pacific Coast, in the lower Fraser Valley and around Okanagan Lake on species of Microtus and Peromyscus. Hystrichopsylla dippiei Rothschild is a large flea with six spines in the genal comb and occurs on a number of rodent species across the province. H. schefferi Chapin which is probably the world's largest flea with four antesensilial setae and six spines in the genal comb, is recorded from Mink (Mustela vison Schreber) and the Spotted Skunk (Spilogale pictorus (L.)) in the lower mainland.
Fleas with eyes vestigial. Head with a genal comb of two flap-like structures located anteriorly on either side of oral margin. A clear, unsclerotized area is present in the preantennal region in some genera. The preantennal and postantennal regions are separated by an interantennal groove. Pronotum with comb of true spines. Mesonotum with pseudosetae under collar. Metanotum with apical spinelets. Anterior abdominal terga with short apical spinelets, or with "false combs" of thickened setae. Typical abdominal terga with two or more rows of setae. The sensillium is flat, and antesensilial setae are present or absent. Females have a single spermatheca.
Worldwide there are 19 genera and 115 species and subspecies. So far four genera and 11 species are recorded from North America. Four species in two genera are known from Canada, with all of these reported from British Columbia.
Species of Ischnopsyllidae are ectoparasites of bats. Nycteridopsylla vancouverensis Wagner, which has the head pointed anteriorly, genal spines somewhat pointed, and a distinct "false comb" on tergum VII, has been recorded from Silver-haired Bat (Lasionycteris noctivagans (LeConte)) in Vancouver. Myodopsylla insiguis (Rothschild) which is rounded on the head anteriorly, and has a "false comb" on tergum VII is the commonest and most widely distributed bat flea in North America, and occurs in central British Columbia on the Little Brown Myotis (Myotis lucifugus (LeConte)). The related M. gentilis Jordan & Rothschild has also been recorded across the province from this same host, while M. palposus (Rothschild) has been collected on the Big Brown Bat (Eptesicus fuscus (Beauvois)) and appears to be restricted to the southern part of the province. The latter flea lacks false combs on the metanotum and abdomen.
Family Leptopsyllidae (Fig.
Head with eyes often minute or vestigial. Arch of tentorium clearly visible in front of eyes. Ocular row of setae with most dorsal seta above the level of upper margin of eye. Genal comb present or absent, but pronotal comb always present. Metanotum with marginal spinelets. Male with sternum VIII not greatly reduced. Wagner's gland absent. Female with anal stylet provided with one or two long sublateral setae in addition to apical setae. Only one spermatheca present in female.
Nine genera and 21 species are noted from North America. Seven genera and 17 species are so far reported from Canada, with five of these genera and eight species recorded from British Columbia.
Leptopsylla segnis (Schönherr) is an alien species that evidently was introduced with domestic rats and mice. With a genal comb with four spines arranged vertically, L. segnis has been collected on the House Mouse (Mus musculus L.) in Kelowna, and elsewhere in Canada is only known from St. John's and Conception Bay, Newfoundland.
Family Pulicidae (Fig.
Eyes large and pigmented, without an internal sinus The antennal fossae are closed. Genal and pronotal combs are present or absent. The mesonotum is without pseudosetae under the collar. The metanotum and abdominal terga lack marginal spinelets. The outer internal ridge of the middle coxae is absent. However, the inner surface of the hind coxae has a row or patch of spiniform setae. The hind tibia lack an outer apical tooth. The spiracles are circular, and that on the metepimeron is larger than those behind. The sensillium has eight or 14 pits on each side. The female has an anal stylet.
Worldwide there are 24 genera and 190 species or subspecies. Eleven genera and 19 species occur in North America. Five genera and seven species are reported from Canada, with four of these genera and five species recorded from British Columbia.
The Human Flea (Pulex irritans L.), which lacks both genal and pronotal combs, is the only flea associated with man an other primates. Although humans are a common host, this flea occurs on a large number of other hosts, including pigs. The Human Flea is well established in the lower mainland and on Vancouver Island, but also has been collected in Kamloops.
However, the fleas most often encountered by humans is not the Human Flea, but either the Dog lea (Ctenocephalides canis (Curtis)) or the Cat flea (C. felis Bouché). These two closely related species have both genal and pronotal combs, and both occur on both cats and dogs. The two species frequently get established in homes, where they can become a nuisance because of their painful bites. Although both the Cat flea and the Dog flea are not uncommon on domestic rates, they have also been collected on the Spotted Skunk (Spilogale putorus (L.)) and the Dog flea has been collected on the Red Fox (Vulpes vulpes (L.)) in Ladner and Mission. In the Dog flea, the first pine on the genal comb is shorter than the second, whereas in the Cat flea, these two are more or less equal in length.
Family Vermipsyllidae (Fig.
Eyes present with an internal sinus. Anterior portion of tentorium conspicuous just in front of the eyes. The club of the antenna is segmented all round, and the antennal fossae do not meet in the interior of the head, the central tuber being absent. The labial palps have five or more segments. The head and pronotum is without either well developed combs or spinelets representing vestigial combs. The metepimeron has long setae, and the spiracle on this sclerite is very near its dorsal margin. The fore femora has the outer seta of the dorso-apical pair shorter than the inner seta. The tarsi of all the legs have four pairs of plantar setae. The second abdominal tergum has two or more rows of setae. The sensillium is transverse, and antesensilical setae are not differentiated in either sex. Females are without an anal stylet.
Species of Vermipsyllidae are ectoparasites of carnivores. Worldwide there are three genera and 31 species. Only the genus Chaetopsylla is reported from North America, with six species on record. Five species are recorded from Canada, with two of these present in British Columbia.
Chaetopsylla tuberculaticeps (Bezzi) is a large flea with a distinctive permanent frontal tubercle on the head, is associated with the Grizzly Bear (Ursus arctos L.) and has been collected from this host at Azure Lake and Wigwam. The abdomen of egg laden females of this flea can swell until the terga and sterna become widely separated by the greatly expanded lateral intersegmental membranes, such that the fleas appear maggot-like, and may be 9 mm in length.
The other species of Vermipsyllidae recorded in British Columbia is the smaller Chaetopsylla setosa Rothschild. This species has a deciduous frontal tubercle on the head and occurs on bears, coyotes, lynx and sometimes cougars and wolverines. Records in British Columbia include specimens from the Coyote (Canis latraus Say) at Eagle River, Sicamous, from Black Bear (Ursus americanus Palles) at Mable Lake, from Lynx (Lynx canadensis Kerr) at Gray Creek, and Wolverine (Gulo gulo (L.)) at Parson.