Siphonaptera. Spanish and Portuguese:

Pulgas. Nahuatl: Tecpintin, sing, tecpin

(Mexico). Quechua: Pique kuna.

Fleas are all too familiar insects. Several species infest pets and domestic animals and bite humans. As bloodsuckers, they transmit diseases, among the more serious, murine typhus (Rickettsia typhi) and plague (Yersinia pestis) (see Medical Entomology, chap. 3).

These are small (BL 1—6 mm), dark brown insects with sclerous bodies that are wingless and strongly compressed laterally. The head projects forward as a rounded shield and bears short, three-segmented, clubbed antennae and sometimes dark ocular spots. The head, thorax, and anterior abdominal segments may also have rows of stiff, flat, scalelike bristles (ctenidia) that aid in mobility through hairs or feathers. The legs and body have prominent setae. The mouthparts are elongated and supremely adapted for bloodsucking with three saberlike stylets and associated palpi and channeled labium. The legs, especially the posterior pair, are much larger and powerfully constructed and give the fleas incredible leaping capabilities (Rothschild et al. 1973).

Fleas are usually confined to animals that customarily burrow and have a den, ground nest, or habitual resting place. Insectivores and rodents are common hosts, but fleas are ectoparasites of owls, swallows, domestic fowl, rodents, bats, and many other mammals (except aquatic ones). Host specificity varies, some flea species being catholic in their tastes, others highly restricted to one host species (da Costa Lima and Hathaway 1946).

Unlike the other ectoparasite orders discussed in this chapter, fleas have complete metamorphosis. The larval stage lives in the soil and organic debris that collects in the host's nest, feeding on cast-off blood, feces, and scurf from the animals living there. After attaining full growth, the larva (fig. 7.3b) spins a cocoon in which it pupates (fig. 7.3e). The pupa is inactive and passes a developmental period of a few days to several months while metamorphosing into the adult flea. Adults remain on the hosts most of the time but must go elsewhere, especially when hosts leave the nest or perish. Eggs are placed randomly, but the timing of egg production is dependent on the reproductive cycle of the host. Copulation and oviposition occur most often prior to nesting, egg laying, or parturition of the vertebrates on which the fleas' life depends.

Blood is the only adult food. When passing into the stomach, the blood courses through a check valve (proven-triculus) lined with hundreds of prominent spines. After the flea has engorged, the valve prevents a back flow of fluid into the foregut. This structure may become clogged with plague bacilli that develop after a blood meal on an infected rat or human. The organisms are regurgitated forward during subsequent feeding attempts and enter the bloodstream of a

Figure 7.3 FLEAS, (a) Cat flea (Ctenocephalides felis, Pulicidae). (b) Cat flea larva, (c) Oriental rat flea (Xenopsylla cheopis, Pulicidae). (d) Rodent flea (Dasypsyllus lasius, Dolichopsyllidae). (e) Cat flea, pupa in cocoon, (f) Chigoe (Tunga penetrans, Tungidae), male, (g) Chigoe, gravid female.

new individual, where the disease can develop.

In Latin America, the flea fauna is diverse and well developed, with a total number of species probably in excess of five hundred, but flea taxonomy in this part of the world is incomplete (Johnson 1957, Traub 1950). The flea fauna of South America is notable for its high percentage of endemic higher taxa. Some, like the Stephanocircidae (helmeted fleas) and Pygiopsyllidae, found elsewhere only in the Australasian region, suggest that the original hosts of fleas were marsupials (Wenzel 1972). Other primarily South American flea families are Malacopsyllidae and Rhopalopsyllidae. The former live on edentates and carnivores; they have enlarged tarsal claws and a leathery integument; the latter are parasites of rodents and a variety of other mammals.

As with other ectoparasites, fleas may be grouped according to those associated with household and husbanded animals, sometimes secondarily attacking humans and probably mostly introduced from the Old World, and indigenous species on wild mammals and wild birds.

Humans suffer mostly from the species found on animals kept in and around homes, because of their shared abode. The dog flea (Ctenocephalides canis) and cat flea (C. felis, fig. 7.3a) are primary in this respect. The Oriental rat flea (Xenopsylla cheopis, fig. 7.3c), another cosmopolitan species, ranges freely from its hosts, often biting people; it is the premier vector of plague. Other domestic rodent fleas are the mouse flea (Leptopsylla segnis) and the northern rat flea (Nosopsyllus fasciatus). The human flea (Pulex irritans) has a wide range of hosts among animals whose lives are encouraged by human activity and is another excellent transmitter of plague, including two unusual types of the disease found in Ecuador, vesicular (virola pestosa) and tonsillar (angina pestosa) forms.

The sticktight flea (Echidnophaga gallina-cea) attaches to unfeathered skin on the head of domestic fowl, causing considerable agitation. It is a relative of the burrowing flea (see below) but rarely infests humans.

Bat fleas form the family Ischnopsyl-lidae and mainly associate with insectivorous chiropteran species. Their droppings provide a better nutrient medium on roost floors than those of the fruit-eating or carnivorous bats. Ceratophyllus (Ceratophyl-lidae) and Dasypsyllus (Dolichopsyllidae, fig. 7.3d) are common genera mainly associated with wild birds.

References da Costa Lima, A. and C. R. Hathaway. 1946. Pulgas: Bibliographia, catálogo e animais por elas sugados. Inst. Ozwaldo Cruz Monogr. 4: 1-522.

Johnson, P. T. 1957. A classification of the Siphonaptera of South America. Entomol. Soc. Wash. Mem. 5: 1-299. Rothschild, M., Y. Schlein, K. Parker, C. Neville, and S. Sternberg. 1973. The

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