5. Palpi long, second segment at least twice as long as wide. Basis

capituli of variable form, roughly rectangular dorsally. Ornate . . . . . . Genus Amblyomma,

The long mouth parts of the Ixodes enable these ticks to be especially painful and annoying parasites of livestock and man.

Thirty-four species of the genus Ixodes have been reported in the United States. Only two species, however, I. pacificus and I, scapularis, are commonly found on livestock. Both species are three-host ticks.

Ixodes pacificus, the California black-legged tick, is commonly found on domestic livestock, deer, and man along the western coast of the United States from Mexico to British Columbia. Records indicate that this species is most abundant during the spring.

Ixodes scapularis Say, the black-legged tick, is found primarily from Texas and Oklahoma eastward to the Atlantic Ocean, but it has been reported as far north as Iowa and Indiana and as far northeast as southern Massachusetts. In the Southern States where this species is commonly found, it is most abundant in late winter and early spring. Although the black-legged tick is not known to transmit any disease, it is a suspected vector of anaplasmosis.

Morphological Characteristics

Anal groove distinct and curving about the anus anteriorly. Inornate. Eyes and festoons absent. Palpi and basis capituli of variable form. Spiracular plates round or oval. Venter of male covered with seven non-projecting, armor-like plates. Sexual dimorphism pronounced especially in regard to the capitulum.

The Species of Ixodes

No attempt has been made to present a key for the identification of the species, because many of the numerous species of Ixodes found in the United States are closely related and difficult to differentiate. In most cases an accurate determination of an unknown specimen may be made only if known specimens are available for comparison and study. It is suggested that all Ixodes may be referred to a specialist for identification.

(See "The Genus Ixodes in North America," by R. A. Cooley and G. M. Kohls, 1945.)

General Comments

The genus Haemaphysalis includes over 50 species. Only 2 species, H. leporis palustris and H. chordeilis, have been reported in the United States. Neither is commonly found on livestock. Both species are three-host ticks.

Haemaphysalis leporis palustris (Packard), the rabbit tick, is widely distributed in the United States from Massachusetts to California. The adult is found primarily on rabbits and groundfrequenting birds; whereas, the larva and nymph are found almost entirely on ground-inhabiting birds. None of the stages are commonly found on livestock or man. This species may be more important than is realized. Evidence indicates that the rabbit tick may be an important factor in the spread of Rocky Mountain spotted fever and tularemia among wild animal reservoir hosts.

Haemaphysalis chordeilis, the bird tick, is also widely distributed in the United States. Birds are the preferred hosts for all stages of the species, and livestock and man are only rarely attacked. Several authorities have reported deaths in turkeys and wild game birds from heavy infestations of this species.

Morphological Characteristics

Inornate. Eyes absent. Festoons present. Usually short conical palpi with second segment projecting laterally beyond the basis capituli which is rectangular in the dorsal view. Usually of small size and sexual dimorphism slight. Ventral plates or shields absent in the male. Posterior margin of coxa I never bifid or deeply cleft. Spiracular plates usually rounded or commashaped in the male, rounded or oval in the female.

The genus Boophilus has been eradicated from the United States--except for a small, narrow quarantine zone along the Texas-Mexico border. Periodic reinfestations in the quarantine zone occur from adjacent heavily infested areas of Mexico.

The cattle fever tick, B. annulatus (Say), was formerly the most common and economically important tick attacking livestock, particularly cattle, in the Southern States. As a vector of Babesia bigemina, the causative agent of cattle fever (bovine piroplasmosis), this tick and the disease it transmits cost the livestock industry an estimated $40 million annually prior to the start of the Tick Eradication Program in 1906.

Boophilus microplus (Canestrini), the tropical cattle tick, has also been found in the United States. It is closely related to B. annulatus, and the females are sometimes difficult to differentiate. Both species are one-host ticks that prefer similar hosts, and both species are vectors of piroplasmosis and anaplasmosis.

As the name implies, the tropical cattle tick prefers a warm climate. In the United States, in the past, it was reported most frequently from Florida and extreme southern Texas. The tropical cattle tick is very prevalent in the Caribbean islands and the West Indies, Central America, and parts of Mexico and South America; also in Australia, Africa, and the Oriental Region.

1

Morphological Characteristics

Very short, compressed palpi, ridged dorsally and laterally. Basis capituli hexagonal dorsally. Eyes present. Inornate. Festoons absent. Spiracular plate rounded or oval. Male with adanal and accessory adanal shields. Anal groove obsolete in female, faint in male. Caudal process present or absent in male.

Key

1. Female: With internal and external spurs of coxa I broadly rounded and wider than long. Coxae II and III with external spurs broadly rounded and wider than long. Coxa IV with or without very small external spur.

Male: With caudal process at posterior extremity of body

2. Female: With internal spur of coxa I absent, external spur broadly rounded and wider than long. Coxae II, III, IV without external spurs. Male: Without caudal process

Boophilus microplus

B. annulatus

GENUS RHIPICEPHALUS

General Comments

In Africa, where this species is common, it is a known vector of bovine piroplasmosis, East Coast fever, pseudo-East Coast fever, and spirochetosis. The common hosts in Africa include numerous wild and domestic animals, including cattle, sheep, goats, swine, horses, camels, and dogs.

Until 1960 the genus Rhipicephalus held a unique position in the United States in that only one species, Rhipicephalus sanguineus, had been reported.

In 1960 an African species, R. evertsi, the red tick, was found on zoo animals in two zoological compounds in Florida. Later the red tick was found on zoo animals at a game farm in New York. The red tick was eradicated from the United States in 1961.

Morphological Characteristics

Palpi short and basis capituli usually hexagonal dorsally. Usually inornate. Eyes and festoons present. Coxa I bifid. Males with a pair of adanal shields and usually a pair of accessory shields. Spiracular plates comma-shaped, short or long.

Key

Eyes hemispherical or "bead-like," set in a depression (orbited) and protruding from it. Scutum dark brown, contrasting with reddish integument and saffron legs. Scutal punctations moderate to large in size. Adanal shields huge, very acute (pointed) anteriorly, and distinctly widened and semi-circular posterolaterally. (Found on zoo animals in Florida and New York.)

Eyes only mildly convex and not set in a depression. Scutum, integument, and legs brown, Scutal punctations small to moderate in size, scattered and not as deep. Large adanal shields, less acute anteriorly, only slightly widened, and somewhat angular posteriorly. . .

Rhipicephalus evertsi

GENUS AMBLYOMMA

General Comments

The genus Amblyomma is represented in the United States by at least seven species, four of which are commonly found on livestock. Those found on livestock include A. americanum, A. cajennense, A. imitator, and A. maculatum. Their distribution is limited usually to the southeastern or southwestern coastal States. The long mouth parts and the color pattern on the scutum are distinctive characters which aid in recognition of Amblyomma attacking livestock in the United States. Two species, A. dissimile, the iguana tick, and A. tuberculatum, the gophertortoise tick, as larvae and nymphs, have attached to and engorged upon bovine. Adults, however, usually attach only to reptiles and amphibians. The engorged adult A. tuberculatum may be almost an inch in length. Another species, A. inornatum, has been collected from dog, cow, coyote, and rabbit in southern Texas.

Amblyomma americanum (Linnaeus), the lone star tick, so named because of the conspicuous pale spot on the posterior of the female scutum, is one of the more economically important species. The long mouth parts and great abundance of this tick make it an especially annoying pest of livestock. The wound produced predisposes livestock to attack by the screwworm fly, Cochliomyia (Callitroga) hominivorax.

The lone star tick is also important from the public health standpoint, because it is capable of transmitting tularemia, Rocky Mountain spotted fever, and American Q fever; and causes tick paralysis in man and in dogs.

The lone-star tick is more widely distributed in the United States than the other Amblyomma species. It is commonly found from Texas north to Missouri and eastward to the Atlantic coast. A. americanum is a three-host tick. It may be active from early spring to late fall and all stages attack livestock and man.

Amblyomma cajennense (Fabricius), the Cayenne tick, has limited distribution in the United States, being confined to a few counties in southern Texas. In tropical Central and South America, this species has been reported abundant, active the year round, and of definite economic importance as a livestock pest. It is a known vector of Rocky Mountain spotted fever in Mexico, Panama, Columbia, and Brazil. A. cajennense is a three-host tick.

Amblyomma hebraeum, the bont tick, an exotic species, has been reported twice in the United States on rhinoceroses imported from South Africa. The ticks were dead when found. This is a three-host tick that causes heartwater in cattle, sheep, and goats.

Amblyomma imitator was, until 1958, confused with A. cajennense. The species has been recorded from man and a variety of domestic and wild animals in Southern Texas, Mexico, and Central America. Its definitive distribution, life history, and economic importance have not yet been determined.

Amblyomma maculatum Koch, the Gulf Coast tick, is an important pest of livestock. The adults are usually found in clusters in the external ear where they produce an intense inflammation. Tick bites predispose the ear to attack by the screwworm fly.

The Gulf Coast tick is found in those States bordering the Gulf of Mexico and along the Atlantic Coast of South Carolina, Georgia, and Florida. This species is rather exacting in its environmental requirements, usually preferring areas of high rainfall, temperature, and humidity. It is seldom found in great number more than 100 to 150 miles from the coast. Livestock are attacked principally during the late summer and early fall. A. maculatum is a three-host tick. The larva and nymph generally feed on birds and small mammals while the adult prefers livestock.

Morphological Characteristics

Palpi long, segment 2 at least twice as long as wide. Generally ornate. Eyes and festoons present. Basis capituli of variable form, usually roughly triangular or rectangular dorsally. Adanal shields absent in the male, but small ventral plaques occasionally present near the festoons. Spiracular plates roughly triangular or comma-shaped.

Key to the Female Species

1. Scutum with scant ornamentation usually limited to a distinct pale spot near the posterior end

Amblyomma americanum

2

2. Metatarsi of legs II, III, and IV with two stout spurs on distal end... Amblyomma maculatum

Metatarsi of legs II, III, and IV without spurs on distal end .

3. Festoons with chitinous tubercles at postero-internal angle.

Festoons without chitinous tubercles.