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A study of the Ixodid ticks of northern Florida, including the biology and life history of Ixodes scapularis Say (Ixodidae: Acarina)

A study of the Ixodid ticks of northern Florida, including the biology and life history of Ixodes scapularis Say (Ixodidae: Acarina)
Andrew Jackson Rogers

1953

Department of Entomology, University of Maryland, College Park, MD 20742, UNITED STATES OF AMERICA.

ABSTRACT

An intensive study or ixodid ticks was conducted in northern Florida during the period from late 1949 through January 1953. Thirteen species, representing five genera, were collected.

Special attention was given to the host relationships, seasonal activities, and habitat distributions of Amblyomma americanum (L.), Dermacentor variabilis (Say), and Ixodes scapularis Say. Biology and life history studies were conducted on Ixodes scapularis.

The habitats studied were (1) flatwoods, characterized by the pine-palmetto association; (2) hammocks, characterized by evergreen hardwoods of various associations; and (3) sandhills, characterized by the longleaf pine-turkey oak association.

The adult of Amblyomma americanum was collected from hosts during every month in the year but was most active from January to August. Adults were collected only from larger mammals. The larvae were collected during every month in the year except March and April. The season of greatest activity was from June through August. The larvae were collected from mammals and birds. Nymphs were collected during every month except November. This stage was quite active throughout the year except during the period from November through February and in June. Nymphs were collected from Mammals and birds. Neither the larvae nor the nymphs were collected from mammals smaller than the gray squirrel. Amblyomma americanum was found to be abundant only in the hammocks. No stage of this species was found in the sandhills that were far removed from hammocks. This species was collected only rarely in flatwoods. It apparently breeds in the small hammocks interspersed among the pine-palmetto associations in the flatwoods.

Amblyomma maculatum Koch was not studied extensively since this species has been studied in southern Georgia. The adults were most prevalent on cows from June through September. The favorite habitat for this tick in northern Florida was found to be the flatwoods. Specimens were collected in small numbers from cattle that ranged only in hammocks. Larvae were collected in one instance on a cloth drag in the sandhills near flatwoods and a hammock.

Amblyomma tuberculatum Marx was recorded in the larval stage from mammals, birds, and one reptile. New host records obtained for the larva are man, bobwhite quail, robin, and fence lizard. The record from the fence lizard is also the first record of the larva from reptiles. The larvae were found to be active only from November through March. Nymphs and adults were found only on the gopher-tortoise. No seasonal activity data were obtained for the nymphs and the adults. This species was collected in the flatwoods and' in the sandhills, but no records were obtained from hammocks.

The adult of Dermacentor variabilis (Say) was collected from dogs during every month in the year. The period of greatest activity began in March, reached a peak in May, dropped gradually during June and July and then more abruptly in August. Only an occasional specimen was round during November, December, January, and February. The tick is of no importance as a pest of dogs during the winter months. The Florida bobcat was found to be an excellent host for the adult and probably is or more importance than the dog as a host for Dermacentor variabilis in the rural areas of northern Florida. This tick was rarely found on cows. The larvae or Dermacentor variabilis were collected from hosts during every month except June. The period or greatest activity for the larvae was from October through February and in August. The nymphs were collected during every month except June and November. Nymphs were more abundant on hosts during the period from December through May. The most important hosts for the larva and the nymph were the cotton mouse and the northern cotton rat. An unengorged larva was taken from the bobwhite quail in two separate instances. This species does not normally infest birds. Dermacentor variabilis was prevalent in the flatwoods and in the hammocks. No records of this species were obtained in the sandhills habitat.

Haemaphysalis chordeilis (Packard) was collected infrequently in the flatwoods habitat. All records were from the meadow lark.

Haemaphysalis leporis-palustris (Packard) was found to be abundant on lagomorphs, and the immature stages were found more frequently than any other tick on birds.

Two female specimens of Ixodes affinis Neumann were collected, one from a dog July 14, 1951, and one from a Florida bobcat October 28, 1951. Both collections were made at Gulf Hammock, Levy county, Florida. The record from the dog is a new host record for this species. There are no previous reports of this species from the United States. However, Doctor Glen M. Kohls, of the U. S. Public Health Service, has an unpublished record of a single female collected in this same locality in Florida during 1948.

All stages of Ixodes bishoppi Smith and Gouck were collected from the northern cotton rat, and the nymphs were collected from the cotton mouse. The record from the cotton mouse is a new host record for this species. Ixodes bishoppi has not been previously reported from Florida, but Doctor Carroll N. Smith has unpublished records of this tick from central Florida.

Two records of Ixodes brunneus Koch were obtained. Two larvae were collected from a towhee January 26, 1949, and one engorged female was collected from a towhee January 26, 1950. Both collections were made in the flatwoods in Alachua County, Florida. This is the first report of Ixodes brunneus from Florida.

Ixodes cookei Packard was collected in three instances from the Florida raccoon; one nymph November 23, 1950, Jefferson County; one nymph November 25, 1950, Taylor County; and two females January 17, 1952, Alachua County, Florida.

Twenty four nymphs of Ixodes texanus Banks were collected from a southern fox squirrel in Taylor County, Florida December 26, 1949. All other collections of this species were females taken from Florida raccoons in the flatwoods in Alachua County. The records are as follows: one December 5, 1949, one January 28, 1950; one September 12, 1950; and four January 17, 1952.

Adults of Ixodes scapularis Say were found to be abundant on cows and dogs. The Florida bobcat appeared to be one of the most important hosts among wild mammals. The immature stages of Ixodes scapularis were found to utilize lizards, especially the skinks, as their principal hosts. The ground skink was found to be the most important host for the larvae. The broad-headed skink and the glass snake appeared to be the most important hosts for the nymphs. New host records for the larvae are the glass snake, Carolina anole, southern golden mouse, northern cotton rat, and Florida deer mouse. New host records for the nymphs are the Florida bobcat and the northern cotton rat.

Adults of Ixodes scapularis were found on hosts only from late September to May. The peak of abundance occurred near the middle of November during 1951 and 1952. Females outnumbered males on hosts at a ratio or approximately two to one. Engorged ticks started dropping in October. The average preoviposition period in field cages was 14.7 days during the period from October through March, with a range of eight to 19 days. Incubation during that period required an average of 81.2 days, with a range of 62 to 89 days.

Larvae were active from January through September with the peak of abundance in early spring, probably April or May. Engorgement of the larvae required from four to 16 days. The time required for engorgement appeared to vary with different hosts. Molting of the larvae in field cages required an average of 21.5 days during July and August, with a range of 20 to 27 days. A small number of larvae that dropped during February and March required from 49 to 66 days to molt.

Nymphs were active from April through November. The peak of activity appeared to be during June, July, and August. Engorgement of the nymph on the broad-headed skink required an average of 10.2 days, with a range of seven to 20 days. During the period June through September 1952 male nymphs required an average of 30.8 days to molt, and female nymphs required an average of 32.9 days to molt. A few nymphs that dropped in November 1952 had not molted four months later. This indicated that nymphs that drop as late as November probably do not molt until the following spring.

The minimum life cycle for Ixodes scapularis in northern Florida was found to be one year. This period was from October to October. There was a strong indication that the life cycle may be extended to two years for ticks that do not drop engorged as nymphs before November.

The larva and the nymph of Ixodes scapularis were found to remain on the soil or in the ground litter at all times. The adult remained quiescent beneath ground litter from June until its season of activity began in the fall. At that time, the adults climbed shrubs and grasses when stimulated by the presence of a host. If a host was not found, the ticks returned to the ground within a few days.

Larvae lived in field cages without food from 14.5 to 24 weeks. The longevity of unfed nymphs in field cages was observed to be from five and one--half weeks to 17 weeks. The longevity of unfed adults in field cages was from eight and one-half to 17 weeks. The longevity of all stages was considerably longer on moist sand in an insectary than in field cages.

Ixodes scapularis mated wherever the two sexes were brought together, on or off a host. The duration of oviposition ranged from approximately six weeks to three months. Low temperatures retarded the rate of oviposition. Fifty degrees Fahrenheit appeared to be near the threshold for egg laying. The maximum number of eggs laid by a fully engorged tick was 2,807; the minimum number recorded was 1,108; and the average number for nine specimens was 2,052.

The male of Ixodes scapularis was never observed attached to a host. Only on one occasion was a male observed to insert its hypostome into the skin of a host. In that instance the hypostome was withdrawn in less than five minutes, and the male coupled with a female near by. It was concluded that the male is of no importance as a parasite.

Comparisons of populations of the adult of Ixodes scapularis in burned and non-burned areas of the flatwoods habitat showed conclusively that this species was more abundant in an area that had not been burned in 14 years than in areas having a range of from one to three years from the date of the last burning to time of sampling, and with a history of frequent burning. It was further shown that there was no significant difference in populations of this tick in the three classes of burned areas studied. The conclusion was that more than three years without fire are required in an area with a history of frequent burning in order for populations of this tick to reach a level comparable to populations that obtain in areas not having been ·burned in 14 years.

Ixodes scapularis was found to be prevalent in the flatwoods and hammock habitats, but no record of this tick was obtained in sandhills that were far removed from other habitats.

Rhipicephalus sanguineus (Latreille) was collected only from dogs and only in domestic environments.