Seasonal patterns of abundance and host relationships of the Australian paralysis tick,Ixodes holocyclus Neumann (Acarina: Ixodidae), in southeastern Queensland

Estimates of seasonal abundance of larvae, nymphs and females of the paralysis tick, Ixodes holocyclus, were obtained by collecting ticks that engorged on small mammals and birds trapped in two localities in southeastern Queensland: Brisbane (wet sclerophyll forest) and Tamborine Mountain (cleared rain forest). The long-tailed short-nosed bandicoot, Isoodon macrourus, was the most common mammal trapped but small numbers of other marsupials, rodents and ground frequenting birds were also captured. Small numbers of five other tick species were also collected. In both habitats there was clearly one dominant generation of I. holocyclus;7er year, although the presence of all stages at most times of the year indicated overlapping of smaller cohorts. Females were most abundant in spring and early summer, larvae in summer-autumn, and nymphs in autumn-winter. I. holocyclus was abundant on I. macrourus and rare on most other mammals and birds captured. At the peak of abundance of each instar, each bandicoot dropped from 500 to 2000 engorged larvae, 100 to 200 engorged nymphs, and four to six engorged females. Life tables were compiled for the tick in both habitats and these indicate that there was relatively high survival from engorged larva to engorged nymph and thence to engorged female and that most mortality occurred between detaching of the engorged female and the detaching of the engorged larva. The tick was more abundant on bandicoots from cleared rain forest and rain forest edge, than on those from sclerophyll woodland. The survival of engorged larvae and nymphs of I. holocyclus and the larval productivity of engorged females were examined in a warm moist climate where the tick was abundant (Tamborine Mountain) and in a hotter dryer climate where the tick was rare or absent (Amberley). In both localities engorged larvae and nymphs survived to the next instar in all seasons of the year. On most occasions engorged females produced eggs which hatched. Mature bandicoots from tick infested areas showed little or no resistance to infestation with larvae or nymphs of I. holocyclus, whereas other small mammals from the same area showed an appreciable degree of resistance to the immature stages of the tick. Feeding larvae and nymphs exposed to normal light-dark cycles in the laboratory detached during the afternoon and early evening. This behaviour and host resistance are discussed in relation to the daily activity cycles of host species, their habitat preferences, and their role as hosts for I. holocyclus.     

Development, survival, and oviposition of the rabbit tick, Haemaphysalis leporispalustris (Packard) (Acari: Ixodidae), at constant temperatures

The relationship between development, survival, and oviposition rates, and five constant temperatures is described for the developing and reproductive life stages of the rabbit tick, Haemaphysalis leporispalustris (Packard). Development was most rapid at 29.7 C for egg and larvae, and 35.6 C for nymphs. Survival was greatest between 14.7 and 29.7 C, but was reduced at 35.6 C for eggs and larvae. Oviposition was optimal between 19.9 and 29.7 C with a maximum mean daily oviposition of 253 eggs/female/day on the third day of oviposition at 29.7 C. Maximum mean total eggs per female produced was 1,157 with a range of 277 to 3,327. The total number of eggs produced per female correlated with the weight of the engorged female. Both linear and sigmoid curve equations were used to approximate the relationship between the temperature and development rates of eggs, larvae, and nymphs. The nymphs had the highest heat requirements of the 3 development stages. Comparisons with field host-parasite data indicate that the rabbit tick has a 2-yr life cycle in southwestern Nova Scotia.     

Life cycle and seasonal development of post-embryonic Argas reflexus (Acari: Argasidae) at two thermally different locations in Central Europe

Seasonal development was investigated in the pigeon tick, Argas reflexus (F.) over a 5-year period. The ticks were kept in desiccators at two deposition sites with different temperature conditions: a warmer attic and a cooler outdoor aviary. The life cycle of A. reflexus consists of the egg, larva, a variable number of two to four nymphal instars and the adult stage. In the cooler aviary, the ticks passed, on average, fewer nymphal instars than in the attic. At both locations, ecdysis of the nymphs and adults occurred only during the summer months, with peak numbers of ticks finishing the moult in August. This consistent pattern was evident irrespective of the feeding date of the preceding developmental stage or the year of observation. The results strongly suggest that nymphs II, nymphs I and larvae fed later than in mid-July, August or September, respectively, entered a state of diapause and, thus, overwintered in the engorged state. Argas reflexus nymphs II from a laboratory stock that were deposited inside the attic showed a remarkably different seasonal pattern of development, even more than 1 year after their deposition. This suggests that a circannual rhythm may be involved in the ticks' seasonal timing. Mortality of the engorged ticks (from repletion to ecdysis of the following stage/instar) was below 1.5% in most cases, irrespective of the season and the location. Unfed larvae survived for a maximum of one year inside the attic, whereas the median survival period of unfed nymphs was at least 3 years at the same location. Based on the present results, the generation time from (F1) egg deposition to oviposition in the F2 generation might be 3-11 years in Central European A. reflexus, depending on the course of development (two or three nymphal instars) and the number of gonotrophic cycles (probably up to six) of the F1. The life span of a single tick might take approximately 7-11 years or even longer.     

Life history of the tick parasitoid Ixodiphagus hookeri (Hymenoptera: Encyrtidae) in Kenya

We conducted laboratory and field experiments to elucidate the life history of Ixodiphagus hookeri, a parasitoid of the ixodid tick Amblyomma variegatum in Western Kenya. Ixodiphagus hookeri females oviposited in unfed host nymphs as well as engorged nymphs, but rarely in engorged larvae. While I. hookeri developed to adults in engorged nymphs, the eggs laid in unfed nymphs disappeared within 2 days after oviposition. As temperature increased, development time of I. hookeri from oviposition to adult emergence in engorged nymphs decreased from 46 days at 23 °C to 35 days at 28 °C, and their immature survival in engorged nymphs decreased from 67% at 23 °C to 22% at 28 °C. No parasitoid adult emerged from hosts at 30 °C. Individual hosts parasitized by single females produced 42–53 adult wasps, 73% of which were females. As a typical pro-ovigenic species, I. hookeri females had an average of 84 mature eggs at emergence and lived only for a few days. When laboratory-reared, unfed nymphs of A. variegatum were attached to cattle for 4–9 days in subsistence farmers’ fields in Western Kenya, 25% of the engorged nymphs and 4% of the unfed nymphs on cattle were parasitized by I. hookeri, demonstrating that I. hookeri females search for and oviposit in A. variegatum nymphs on cattle. Unlike other strains of I. hookeri that overwinter as eggs in unfed nymphs, I. hookeri could continuously reproduce throughout the year in Western Kenya.     

Life cycle and seaonal development of postembryonicArgas reflexus (Acari: Argasidae) at two thermally different locations in Central Europe

Seasonal development was investigated in the pigeon tick,Argas reflexus (F.) over a 5-year period. The ticks were kept in desiccators at two deposition sites with different temperature conditions: a warmer attic and a cooler outdoor aviary. The life cycle ofA. reflexus consists of the egg, larva, a variable number of two to four nymphal instars and the adult stage. In the cooler aviary, the ticks passed, on average, fewer nymphal instars than in the attic. At both locations, ecdysis of the nymphs and adults occurred only during the summer months, with peak numbers of ticks finishing the moult in August. This consistent pattern was evident irrespective of the feeding date of the preceding developmental stage or the year of observation. The results strongly suggest that nymphs II, nymphs I and larvae fed later than in mid-July, August or September, respectively, entered a state of diapause and, thus, overwintered in the engorged state.Argas reflexus nymphs II from a laboratory stock that were deposited inside the attic showed a remarkably different seasonal pattern of development, even more than 1 year after their deposition. This suggests that a circannual rhythm may be involved in the ticks' seasonal timing. Mortality of the engorged ticks (from repletion to ecdysis of the following stage/instar) was below 1.5% in most cases, irrespective of the season and the location. Unfed larvae survived for a maximum of one year inside the attic, whereas the median survival period of unfed nymphs was at least 3 years at the same location. Based on the present results, the generation time from (F₁) egg deposition to oviposition in the F₂ generation might be 3–11 years in Central EuropeanA. reflexus, depending on the course of development (two or three nymphal instars) and the number of gonotrophic cycles (probably up to six) of the F₁. The life span of a single tick might take approximately 7–11 years or even longer.     

Influence of temperature and relative humidity on the moulting success of Amblyomma limbatum and Aponomma hydrosauri (Acari: Ixodidae) larvae and nymphs

This study compared the duration of the moulting periods of engorged larvae and nymphs of the ixodid ticks, Amblyomma limbatum and Aponomma hydrosauri, at different temperature/relative humidity regimes, and examined the relationships between the engorged weight of ticks and their weights after moulting. The results showed that for each species, there was a significant relationship between the weights of unfed nymphs and engorged larvae, and the weights of unfed adults and engorged nymphs. The weight of engorged nymphs was also a good indicator of their sex, with female ticks having heavier weights as engorged nymphs. Temperature and relative humidity had a marked effect on the moulting success of engorged ticks of both species. Aponomma hydrosauri larvae and nymphs were able to moult at lower temperatures than Amb. limbatum but most ticks, except Ap. hydrosauri larvae, failed to moult at 13 degrees C. Additionally, there was a marked decrease in the pre-moult times of ticks at higher temperatures, with larvae taking less time to moult than nymphs. At temperatures greater than 21 degrees C, Amb. limbatum took less time to moult than Ap. hydrosauri but this interspecific difference was less marked for nymphs. The interspecific differences in the responses of engorged larvae and nymphs to different temperatures and relative humidities correlated with interspecific differences in off-host behaviour and with the different climates the two species experience throughout most of their distributional range.     

Habitat requirements of the seabird tick, <Emphasis Type="Italic">Ixodes uriae</Emphasis> (Acari: Ixodidae), from the Antarctic Peninsula in relation to water balance characteristics of eggs,nonfed and engorged stages

The seabird tick Ixodes uriae is exposed to extreme environmental conditions during the off-host phase of its life cycle on the Antarctic Peninsula. To investigate how this tick resists desiccation, water requirements of each developmental stage were determined. Features of I. uriae water balance include a high percentage body water content, low dehydration tolerance limit, and a high water loss rate, which are characteristics that classify this tick as hydrophilic. Like other ticks, I. uriae relies on water vapor uptake as an unfed larva and enhanced water retention in the adult, while nymphs are intermediate and exploit both strategies. Stages that do not absorb water vapor, eggs, fed larvae and fed nymphs, rely on water conservation. Other noteworthy features include heat sensitivity that promotes water loss in eggs and unfed larvae, an inability to drink free water from droplets, and behavioral regulation of water loss by formation of clusters. We conclude that I. uriae is adapted for life in a moisture-rich environment, and this requirement is met by clustering in moist, hydrating, microhabitats under rocks and debris that contain moisture levels that are higher than the tick's critical equilibrium activity.     

Reason for fluctuation in the demographic structure of the taiga tick population (Ixodidae) in dark conifer-leaf forests of Kemchug Upland

It was found out, that mean ratio of unfed taiga ticks Ixodes persulcatus having a life cycle of 3-5 and 6 years counts respectively (N = 6) 33.6, 52.8, 13.2 and 0.4%. Data on absolute number of I. persulcatus individuals in the process of onthogenesis is given. It is shown, that mortality of different unfed stages increases from larva to imago. In the autumn-winter period, the mean ratio of eliminated individuals counted 16% of larvae, 20% of nymphs, and 38 of imago. The mortality in the spring-summer period caused mainly by the deficit of hosts and counted for these stages 3, 82 and 98% respectively. Engorged ticks successfully undertake unfavorable conditions both in the spring-summer and autumn-winter periods. Their mean mortality in the period from feeding to moulting does not exceed 12%.     

Ant predation on different life stages of two Australian ticks

Laboratory colonies of Rhytidoponera ants were allowed to prey on the fed and unfed stages of the Australian ticks Aponomma hydrosauri and Amblyomma limbatum. The unfed tick stages had a higher survival than the fed stages. The ants took longer to handle the adult ticks than the nymphs and longer to handle the nymphs than the larvae. The ants also took longer to handle the unfed than fed nymphs, but longer to handle the fed than unfed females. As well as the differences between the tick stages, there was a species effect, with the ants taking longer to handle A. limbatum, and with that tick species having a higher survival than A. hydrosauri after ant predation. These stage and species differences may influence the tick population dynamics. This revised version was published online in November 2006 with corrections to the Cover Date.     

Methods for estimating the demographic structure of the taiga tick (Ixodidae) based on results of standard parasitological observations

A retrospective estimation of the abundance dynamics of the taiga tick Ixodes persulcatus in mixed coniferous and leaf-bearing forests of the Udmurtia Republic in the period 1957-1986 was carried out. A possibility to estimate the absolute number of all stages of I. persulcatus based on relative indices. Females of I. persulcatus lay 20,250 eggs per 1 hectare, and this number of eggs gives birth to 15,000 larvae. From this number, 7870 larvae hibernate and 6550 individuals became fed. The number of nymphs is 5930, among which 5110 individuals live up to spring, and 1390 became fed. The number of adult mites in autumn is 1250; in subsequent spring this number decreases to 780. The mean number of engorged females is 8. The mortality rate of ticks caused by the deficit of hosts increases from preimaginal stages to adults; for larvae, nymphs and imago this index is 16.6, 72.8, and 97.9%, respectively. Quotas of individuals with 3-, 4- and 5-year life cycle among the unfed imago are 70.4, 28.0, and 1.6%, respectively.     

Pathogenicity of entomopathogenic fungi to different developmental stages of Rhipicephalus sanguineus (Acari: Ixodidae).

The pathogenicity of 4 species of entomopathogenic fungi (Hyphomycetes species: Beauveria bassiana, Metarhizium anisopliae, Metarhizium flavoviride, and Paecilomyces fumosoroseus) to various developmental stages of Rhipicephalus sanguineus (Acari: Ixodidae) ticks was compared under laboratory conditions. The most virulent isolate, M. anisopliae-108, caused 92-96% mortality to unfed larvae and nymphs on day 7 postinfection (PI) and 100% mortality to unfed adults and engorged females on day 21 PI. The pathogenicity of M. anisopliae-108 to engorged larvae and nymphs was lower--82.6 and 60%, respectively. All tested B. bassiana, M. flavoviride, and P. fumosoroseus isolates were significantly less virulent (P < 0.05) or avirulent toward most life stages of R. sanguineus. The M. anisopliae and M. flavoviride isolates also prevented or reduced the ability of the ticks to lay eggs several days before their deaths. Female ticks infected by the fungi achieved only 11.3-60.8% of their egg-laying capacity compared with the controls.     

Drop off rhythm and survival periods of <Emphasis Type="Italic">Amblyomma lepidum</Emphasis> (Acari: Ixodidae) under field conditions

In this study, engorged Amblyomma lepidum ticks were found to drop off in two peaks, one in the morning and one in the evening. Most larvae and females engorged during the morning hours between 06.00 h and 10.00 h with a peak around 08.00 h, whereas the majority of the nymphs dropped in the evening between 18.00 h and 24.00 h with the peak around 22.00 h. Although the effect of time on drop-off patterns of the ticks was statistically significant (p≤ 0.001), there were no significant seasonal influences. Survival of unfed stages of A. lepidum was also studied and was found to increase from larvae to adult ticks. The longest survival periods of 10, 11 and 14 weeks were recorded during the wet season for larvae, nymphs and adults, respectively. It is concluded that environmental conditions required for survival of A. lepidum are optimal only during the wet season and that during other seasons the tick depends primarily on prevailing micro-climatic conditions for its survival.     

Amplification of tick-borne encephalitis virus infection during co-feeding of ticks

Abstract. Following engorgement of Rhipicephalus appendiculatus larvae on guinea-pigs infected with tick-borne encephalitis (TBE) virus, none of the engorged larvae or emergent nymphs contained detectable infectious virus. However, one of twelve pools, each containing three of the unfed nymphs, was positive when screened by polymerase chain reaction (PCR), indicating a low prevalence of TBE virus infection in the unfed nymphs. After engorgement of the nymphs on four uninfected guinea-pigs, 19/24 (79%) fed nymphs from one guinea-pig and 4/25 (16%) fed nymphs from a second guinea-pig were infected; all the ticks examined from the other two guinea-pigs were uninfected. The results suggest that TBE virus was transmitted from a low proportion of infected nymphs (infected as larvae) to uninfected nymphs as they fed together on an uninfected guinea-pig. Such amplification of the initial infection, at the population level, could play an important role in maintaining TBE virus infections in nature, particularly if there is a low level of vertical transmission from one tick generation to the next.     

Absence of insect juvenile hormones in the American dog tick,Dermacentor variabilis (Say) (Acari:Ixodidae), and in Ornithodoros parkeri Cooley (Acari:Argasidae)

Synganglia, salivary gland, midgut, ovary, fat body and muscle alone and in combination from the ixodid tick, Dermacentor variabilis (Say), or the argasid tick, Ornithodoros parkeri Cooley, were incubated in vitro in separate experiments with L-[methyl-(3)H]methionine and farnesoic acid or with [1-(14)C]acetate. Life stages examined in D. variabilis were 3 and 72 h old (after ecdysis) unfed nymphs, partially fed nymphs (18 and 72 h after attachment to the host), fully engorged nymphs (2 d after detachment from host), 3 and 72 h old (after eclosion) unfed females, partially fed unmated females (12-168 h after attachment to host) and mated replete females (2 d after detachment from the host). Those from O. parkeri were third and fourth stadium nymphs and female O. parkeri, 1-2 d after detachment. Corpora allata from Diploptera punctata, Periplaneta americana and Gromphadorina portentosa were used as positive controls in these experiments. No farnesol, methyl farnesoate, JH I, JH II, JH III, or JHIII bisepoxide was detected by radio HPLC from any tick analysis while JH III, methyl farnesoate, and farnesol were detected in the positive controls. To examine further for the presence of a tick, insect-juvenilizing agent, Galleria pupal-cuticle bioassays were conducted on lipid extracts from 10 and 15 d old eggs, unfed larvae (1-5 d after ecdysis), unfed nymphs (1-7 d after ecdysis), and partially fed, unmated female adults (completed slow feeding phase) of D. variabilis. Whole body extracts of fourth stadium D. punctata and JH III standard were used as positive controls. No juvenilizing activity in any of the tick extracts could be detected. Electron impact, gas chromatography-mass spectrometry of hemolymph extracts from fed, virgin (forcibly detached 7 d after attachment) and mated, replete (allowed to drop naturally) D. variabilis and fully engorged (1-2 d after detachment) O. parkeri females also failed to identify the common insect juvenile hormones. The same procedures were successful in the identification of JH III in hemolymph of fourth stadium D. punctata. Last stadium nymphal (female) O. parkeri implanted with synganglia from second nymphal instars underwent normal eclosion to the adult. The above studies in toto suggest that D. variabilis and O. parkeri do not have the ability to make the common insect juvenile hormones, and these juvenile hormones do not regulate tick metamorphosis or reproduction as hypothesized in the literature.     

Factors regulating predation by first-instar spined assassin bugs [Sinea diadema (Fabricius)] (Hemiptera: Reduviidae)

Selected nutritional and developmental factors regulating the predatory behavior of first-instar spined assassin bugsSinea diadema (Fabricius) (Hemiptera: Reduviidae) were investigated. The longevity of unfed nymphs provided with free water, bean pod sections, or glucose solutions was not significantly greater than that of unfed nymphs which were not provided with a source of water. First-instarS. diadema that were provided with larvae ofEphestia kuehniella Zeller (Lepidoptera: Pyralidae) as prey began feeding 1.9 (±0.9) days after hatching. In contrast, first-instarS. diadema that were provided with conspecifics of the same age did not begin feeding until they were 3.9 (±0.9) days old. These results suggest that the potential nutritional benefits to be gained from feeding equal or outweigh the risk of attacking prey capable of effective self-defense only when nymphs have not fed for 4 days after hatching. Providing the nymphs with water or glucose solutions significantly delayed the onset of conspecific predation. Additional data are presented which demonstrate that first-instarS. diadema are not restrained from preying on siblings by kin recognition.     

Sense organs in post-embryonic stages of Hyalomma marginatum marginatum Koch, 1844 (Acari: Ixodida: Ixodidae). I. Tarsal sensory system.

Light and scanning electron microscopic studies showed the differences in morphology and in size of Haller's organ in larvae, nymphs and adults (females and males) of Hyalomma marginatum marginatum Koch, 1844. The length of the anterior pit setae increases during post-embryonic development. The localization of these setae is the same in all stages. Six setae (one porose seta, two grooved setae, two fine setae, one conical seta) contain anterior pit of various developmental stages. In nymphs and adults more numerous pores appear on the wall surface of porose seta than in the larval stage. The structure of the capsule roof also differs in various developmental stages. Haller's organ of Hyalomma m. marginatum shows great degree of morphological development which is connected with the complicated life cycle and feeding behaviour of this tick species.     

Biology of Triatoma flavida Neiva, 1911 (Hemiptera: Reduviidae) under laboratory conditions

The complete life cycle of Triatoma flavida, weekly fed on hens, was studied at 28+/-2 degrees C and 80+/-10% RH. Aspects related to hatching, life span, mortality and feeding behavior for each stage of its life cycle were evaluated. The hatching rate observed for 100 eggs was 93% with an average incubation period of 27.2 days. Sixty-two nymphs completed the cycle and the mean egg to adult development time was 230.4 days. Mean duration of 1st, 2nd, 3rd, 4th and 5th instar nymphs was 22.1, 25.3, 36.7, 49.7 and 69.4 days, respectively. The number of blood meals on each nymphal stage varied from 1 to 7. The mortality rate was 6.5% for NI, 23% for NIII and 7.5% for NV nymphs. Mean number of laid eggs per female was 283.1. Adult survival rates were 344.8 +/- 256.4 days for males and 285.3 +/- 201.8 days for females.     

Parasitism of lizards by immature stages of the blacklegged tick,Ixodes scapularis (Acari,Ixodidae)

From 1982–1985 and 1993–1999, a total of 309 individual reptiles, mostly lizards and snakes, belonging to 12 species (American alligator, six lizard species, five snake species) was captured on St. Catherine's Island, Liberty County, Georgia, USA, and examined for ticks. Three lizard species, the broad-headed skink Eumeces laticeps, southeastern 5-lined skink Eumeces inexpectatus, and eastern glass lizard Ophisaurus ventralis, were severely infested with larvae and nymphs of the blacklegged tick, Ixodes scapularis. Ticks were not found on any of the other reptile species. Overall, 80% of 65 E. inexpectatus examined were parasitized by a mean intensity of 21.5larvae and 88% were parasitized by a mean intensity of 4.8 nymphs. Corresponding figures for E. laticeps (n=56) were 93% and 51.3 for larvae and 89% and 7.4 for nymphs, and for O. ventralis (n=3) were 67% and 22.5 for larvae and 100% and 21.3 for nymphs. Larvae and nymphs attached along the lateral grooves of O. ventralis. Nymphs attached mainly behind the ears and in the foreleg axillae whereas larvae mainly attached to these sites and on the hindlegs in Eumeces spp. Seasonally, both larvae and nymphs were recorded on lizards from April through October. A unimodal larval peak was recorded in May or June. Seasonal data for nymphs did not reveal any distinct peaks but small bimodal peaks in mean intensities may have occurred (one in early summer, the other in late summer)suggesting that some ticks complete their life cycle in one year, and others in two years, on St. Catherine's Island. Potential epidemiological consequences of these findings with respect to Lyme disease in the southeastern United States are briefly addressed. This revised version was published online in August 2006 with corrections to the Cover Date.     

Variability of the life cycle duration in the taiga tick from mixed coniferous-broad-leaved forests of the Udmurt Republic

Seasonal cohorts of the unfed Ixodes persulcatus imago in the study area were found to consist of the ticks passed through three-, four-, and five-year life cycles, in the ratio 72.6, 26.4, and 2.0% respectively, on the base of mean long-term values. Such ratio is established if 91.7% of larvae and 79.9% of nymphs develop without diapause, while the rest of larvae and nymphs develop with diapause. Mean duration of the tick generation is 3.3 years, with the fluctuations in certain of the years within the limits of 3.15-3.36 years.     

The life cycle of Amblyomma neumanni Ribaga, 1902 (Acari: Ixodidae) in the laboratory

A colony of Amblyomma neumanni was started with engorged females collected from cattle in the province of Salta (24° 51S, 65° 33W), Argentina. The larvae and nymphs were fed on rabbits and the adults on calves. The non-parasitic stages were maintained in darkness at 27 ± 1°C and 83–86% RH. The life cycle (pre-feeding period not tested) had a mean duration of 205.7 days. The mean time (days) for the different phases of the cycle were as follows: feeding of females 8.8, pre-oviposition 23.8, oviposition 41.4, minimum egg incubation 76.1, feeding of larvae 8.5, pre-moult to nymphs 16.4, feeding of nymphs 7.9 and pre-moult to adults 22.8. The mean recovery rates of larvae, nymphs and females were 83.8, 85.6 and 89.3%, respectively. The nymphs moulting to females were heavier (8.1 ± 2.34 mg) than those moulting to males (6.0 ± 2.34 mg; p < 0.01), but their range of engorgement weight showed overlap (2.3–16.2 versus 2.2–12.8 mg, respectively). Two gynandromorphs were detected between the nymphs. A comparison of biological parameters of A. neumanni with other American Amblyomma species from mammals is presented. © Rapid Science Ltd. 1998