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*Corresponding author. 
 

11 

Agricultural and Marine  Sciences, 8(1):11-14 (2003) 
©2003 Sultan Qaboos University 
 
 
 
 

Life Cycle and Survival of Hyalomma 
dromedarii (Acari:Ixodidae) Under 

Laboratory Conditions 
 
 

A.M. Alahmed* and S.M. Kheir 
 

College of Agriculture, King Saud University, P. 0. Box 2460, 
Riyadh 11451, Saudi Arabia 

   
 
 
 

!
!
 

 
 
 
 
 
 
 
 
 
 
 
ABSTRACT: The life cycle of Hyalomma dromedarii Koch (Acari:Ixodidae) on rabbits at 25 and 32ºC was compared 
at 85% R.H. At these temperatures, it behaved as a two-host tick and completed its life cycle in 108-146 and 80-115 
days, respectively.  The preoviposition, incubation and moulting periods varied significantly and were influenced by 
temperature. The survival periods of different developmental stages of Hyalomma dromedarii at 25ºC, 32, 38, 43, and 
48ºC at 85% R.H. were investigated. The eggs, engorged nymphs and engorged females died at 38ºC, and the unfed 
larvae died at 43ºC. The longevity of the unfed adults decreased from 90-120 days at 25ºC to7-15 days at 43ºC.  They 
died at 48ºC. These results suggest that the survival periods of eggs, engorged nymphs and engorged females were 
significantly decreased with an increase in temperature.  They were more susceptible to high temperature than unfed 
adults. The role of unfed adult in the continuity of the life cycle of the tick throughout the year is discussed. 
 
Keywords: Hyalomma dromedarii, life cycle, survival, laboratory conditions. 

 
 
 
 

he camel tick, Hyalomma dromedarii Koch (Acari: 
Ixodidae) is the most important tick infesting 

camels in Saudi Arabia (Badawi, 1994). The ecology 
and the biology of the camel tick has not been fully 
investigated. The availability of information on the 
effect of temperature and humidity on the rate of 
development and survival of the camel tick is essential 
for a rational control program. The current study was 
carried out to assess the life cycle of H. dromedarii and 
its survival at different temperatures under laboratory 
conditions. 

Materials and Methods 
 

Fully engorged females of H. dromedarii were 
obtained from a camel in Muzahmyia area (50 Km 
South of Riyadh City) and identified as H. dromedarii 
according to Hoogstraal (1956). They were put in an 
incubator at 28°C and 85% R.H. to oviposit. The 
emerged larvae, nymphs and adults were fed on white 
New Zealand tick-native rabbits. 

Five white New Zealand tick-native rabbits were 
infested with approximately 200 larvae of H. dromedarii. 

T 

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ALAHMED AND KHEIR 
 
 

 12

The engorged nymphs dropped were weighed and the 
mean engorged weight was determined. The larval-
nymphal feeding period was calculated as from 
attachment of unfed larvae to detachment of engorged 
nymphs. The engorged nymphs dropped were collected 
and divided into two groups, each consisted of 50 
nymphs, then incubated at 25 and 32°C, respectively at 
85% RH to moult and the moulting period was 
determined. In a second group consisting of 5 white 
tick-native rabbits, each rabbit was infested with 8 
adults H. dromedarii (sex ratio 1:1). The replete 
females were collected after their detachment, weighed 
separately and the time taken to engorge was recorded 
(from attachment to detachment) and then divided into 
two groups and incubated at 25°C  and 32°C, 
respectively to oviposit.  The incubated ticks were 
observed daily from detachment until oviposition to 
determine the preoviposition period. Eggs were 
observed daily from initiation of oviposition until the 
eclosion of the first larva, to establish the incubation 
period. The weight and number of eggs laid per female 
as well as hatchability were recorded. The mean index 
of conversion efficiency (CEI) was calculated as 
follows: 

 
CEI = [weight of eggs (mg) / weight of replete 

female (mg)]  x 100 
 

About 500 mg of viable eggs, 100 unfed larvae, 50 
engorged nymphs, 30 unfed adults (sex ratio 1: 1) and 
10 engorged females of H. dromedarii were incubated 
at 25, 32, 38, 43, and 48°C at 85% R.H.  All these 
developmental stages were observed daily for their 
survival at these conditions. Eggs, engorged nymphs 
and engorged adults were considered as dead when they 
failed to hatch, moult or lay eggs, respectively. Unfed 
ticks were considered as dead when they did not react 
to mechanical or physical stimuli. For statistical 
analysis, the student's t-test and analysis of variance 
(Steel and Torrie, 1981) were used.  
 

Results 
 
LIFE CYCLE OF H. DROMEDARII:  The results showed 
that at 25°C there was a two-host type of development 
during a period of 108-146 days.  Almost half of this 
period was spent for egg development. The larvae 
remained attached to the host and dropped as engorged 
nymphs.  The preoviposition and incubation periods at 
25°C  were 5-8 and 56-68 days, respectively (Table 1). 
The larval-nymphal feeding period was 11-16 days, and 
the nymphs required 14-24 days to develop into adults. 
The unfed females took 10-14 days to engorge on 
rabbits after which they dropped off to lay eggs.  

At 32ºC, H. dromedarri behaved as a two-host tick 
and completed its life cycle in 80-115 days (Table 1). 
The larvae remained attached to the host for 11-16 days  

TABLE 1 
 

Life cycle of Hyalomma dromedarii on rabbits under 
laboratory conditions.     

Time (days) 
Range (x ± sd) 

Parameter 

25ºC 32ºC 
     
Preoviposition 
period 

5-8       (6.6 ± 1.1)a 3-6 (4.3 ± 0.8)b 
     
Incubation 
period 

56-68   (62.0 ± 5.0)c 34-50 (42.0 ± 5.0)d 
     
Hardening 6-8     (7.0 ± 0.8)a 6-7 (6.5 ± 0.4)a      
Nymphal 
feeding period 

11-16    (14.0 ± 1.8)e 11-16 (13.0 ± 1.7)e 
     
Moulting of 
nymph 

14-24    (19.0 ± 4.0)f 10-15 (12.0 ± 2.0)e 
     
Female 
engorge 

10-14    12.0 ± 1.7)e 10-14 (12.0 ± 1.8)e 
     
Total 108-146   127.0 ± 13)g 80-115 (96.0 ± 11)h 

 
x – mean value;  sd – standard deviation 
Means in a row followed by different letters are significantly different 
(P<0.05 – P<0.001). 
 
and dropped off as engorged nymphs. The nymphs 
required 10-15 days to moult to adults and remained for 
6-7 days in the non-feeding stage. The unfed female 
took 10-14 days to engorge on rabbits and then dropped 
off to lay eggs. The preoviposition and incubation 
periods were 3-6 and 34-50 days, respectively.  The 
results showed that the preoviposition, incubation and 
moulting periods of the tick at 25ºC were significantly 
longer than at 32ºC (P<0.05), while the feeding periods 
of the adults, nymphs and larvae on the host were not 
affected by temperature (P>0.05).  At 25 and 32°C, the 
incubation periods were significantly longer than the 
preoviposition periods (P<0.001), larval-nymphal 
feeding periods (P<0.001) and adult feeding periods 
(P<0.001). At 25°C, the moulting period of the nymphs 
to adult was significantly longer than larval-nymphal 
feeding and adult feeding periods (P<0.05); while at 
32ºC, the temperature had no effect on the length of the 
moulting period, larval-nymphal feeding period  and 
adult feeding period (P>0.05).  

Table 2 shows that the mean engorged weight of 
replete females at 25ºC was 981 ± 218 mg and the mean 
weight of egg mass laid was 588 ± 112 mg, which 
hatched into 8076 ± 989 eggs. The mean index of conversion 

 
TABLE 2 

 
Feeding of Hyalomma dromedarii on rabbits at 25ºC.  

  
Engorged wt  (x ± sd mg) 981.0  ±  218 
Weight of eggs (x ± sd mg) 588.0  ±  112 
No. of eggs (x ± sd) 8076.0  ±  989  
Hatchability (%)               99.0 
Nymphal engorge wt (x ± sd mg) 395.0  ±  84 
I.C.E.                 0.6 

 
x – mean value; sd – standard deviation 
I.C.E. – Index of Conversion Efficiency. 



LIFE CYCLE AND SURVIVAL OF HYALOMMA DROMEDARII  
 
 

 13

TABLE 3 
 

Survival of Hyalomma dromedarii under laboratory 
conditions in days (x ± sd) at different temperatures.    

Temperature 
Stage 

25ºC 32ºC 38ºC 43ºC 48ºC 
      
Eggs 40 -59 22-31 Died   
 50 ± 8a*1 27 ± 3b*1    
      
Unfed 
larvae 

38-50 
44 ± 4a 

26-38 
33 ± 6c 

5-6 
5.5 ± 0.4d 

Died 
 

      
Engorged 
nymphs 

15-23 
19 ± 3e*2 

10-15 
12.5 ± 2f*2 

Died 
  

      
Unfed 
adults 

90-120 
105 ± 13g 

40-65 
52 ± 10h 

20-29 
25 ± 3i 

7-15 
11 ± 3j 

Died 

      
Engorged 
adults 

22-30 
26 ± 3k*3 

14-23 
18 ± 3m*3 

Died 
  

       
x – mean value; sd – standard deviation; *1 – then hatched; *2 – then 
moulted; *3 – then laid eggs. 
Means in a row followed by different letters are significantly different 
(P<0.05 – P<0.001). 
 
 
efficiency was 0.6. There was a strong positive 
correlation between the engorged weight and weight 
of eggs laid  (r = 0.7164) and between engorged weight 
and number of eggs laid (r =0.6872). 

Table 3 shows that all life stages of H. dromedarii 
survived normally at 25ºC and 32ºC, but the survival 
period of eggs at 25 ºC (50 ± 8 days) was significantly 
longer than at 32ºC (27 ± 3 days) (P<0.001).  They died 
at 38ºC. There is a progressive significant decrease in 
survival period of unfed larvae with an increase in 
temperature. Their survival period decreased from 44 ± 
4 days at 25ºC to 5.5 ± 0. 5 days at 38ºC (P<0.001).  
They died at 43ºC.  The survival period of engorged 
nymphs at 32ºC was significantly shorter than that at 
25ºC (P<0.05). The longevity of unfed adults decreased 
significantly from 105 ± 13 days at 25ºC to 11 ± 3 days  
at 43ºC (P<0.001).  They died at 48ºC.  The survival 
period of engorged females at 32ºC was significantly 
shorter than that at 25ºC (P<0.05).  At both 25 and 
32ºC, the survival periods of unfed  adults were 
significantly longer than that of eggs (P<0.001), unfed 
larvae (P<0.001), engorged nymphs (P<0.001) and 
engorged adults (P<0.001). 

 
Discussion 

 
This study has shown that temperature is an 

important factor affecting the duration of 
preoviposition, incubation and moulting periods during 
the development of H. dromedarii. In general, high 
temperature increases the metabolic rate of 
poikilothermic organisms (Chapman, 1976), which in 
turn increases the rate of physiological processes 
involved in egg production resulting in a decrease in 
preoviposition and incubation period length. The results 
obtained in this study are similar to those reported by 
Hagras and Khalil (1988) and Ouhelli (1994) using H. 

dromedarii; Despins (1992) using Dermacentor nitens; 
and Sunder et al. (1999) using Hyalomma anatolicum. 
The duration of developmental periods of different 
stages in the life cycle of H. dromedarii observed in 
this study are longer than those reported by Delpy and 
Gouchey (1937) and Honzakova (1971) for Hyalomma 
dromedarii. These variations are probably due to 
differences in rearing conditions (host and temperature). 

Different types of developments have been 
reported for H. dromedarii. In our study, H. dromedarii 
fed on rabbits behaved as a two-host tick. Das and 
Subramanin (1972) found that H. dromedarii fed on 
sheep or cattle have a three-host life cycle, but 60% of 
the population became a two-host tick when fed on 
rabbits. Ouhelli (1994) found that H. dromedarii was 
usually a three-host tick, but became a two-host tick 
when density on the host was high. Similarly, Latha et 
al. (1998) found that when young larvae of H. 
marginatum (three months old) were fed on rabbits, 
they behaved as a three host tick, while larvae older 
than four to six months behaved as a two host tick. 
From these studies it seems that the type of the host, 
rearing conditions, density and age of the larvae may 
influence the life cycle of the tick. 

In arid zones, where H. dromedarii is widespread, 
low relative humidity has an inhibiting effect on egg 
development (Ouhelli, 1994). The peripheral layer of 
eggs shell was quite desiccated.  This may help in egg 
development during short-lived periods of drought and 
stress under field condition. In this study, almost half of 
the life cycle was spent for egg development.  This may 
be a survival mechanism that permits H.dromedarii to 
survive in arid zones. 

Our study has revealed that eggs, engorged 
nymphs, and engorged females are more susceptible to 
high temperature than the unfed adult. Similar results 
were reported by Delpy and Gouchey (1937) who 
found that when H. dromedarii behaved as a three-host 
tick, unfed larvae and unfed nymphs resist dry 
atmosphere more than engorged stages. 

In nature, the engorged female Boophilus 
annulatus (Say) (Hunter and Hooker, 1907) and Ixodes 
ricinus (L) (Milne, 1950) burrow a few centimeters 
below the ground surface to find favorable microhabitat 
for egg deposition and survival during dry season. In 
Saudi Arabia, probably during the dry season, the adult 
H. dromedarii live in burrows or burrow a few 
centimeters to find a  favorable microhabitat that 
protects the eggs and emerging larvae against high 
temperature and low humidity. 
 

Conclusions 
 

 The type and duration of H. dromedarii development 
were largely influenced by temperature and the host. 
The study has shown that unfed adult ticks were more 
resistant to high temperature than eggs, unfed larvae, 



ALAHMED AND KHEIR 
 
 

 14

engorged nymphs and engorged females. During the dry 
hot season the adult tick burrows a few centimeters below 
the ground surface to find a favorable microhabitat for its 
survival. Control measures using acaricides should be 
directed towards the adult stage. The spray of infested 
hosts at the onset of dry season is highly recommended.  
Further studies  on the seasonal dynamics and host-vector 
relationship of the tick are required.    

 
References 

 
 
Badawi, A.I. 1994. Arthropods of Medical and Veterinary Importance 

in Saudi Arabia.  King Saud University Press, Riyadh. pp 266.  
Chapman, R.F. 1976. The Insect: Structure and Function. Elsevier, 

North Holland, New York. 
Das, H.L. and  G. Subramanian. 1972. Biology of Hyalomma dromedarii 

Koch, 1844 (Acari:Ixodidae). Indian Journal of  Animal Science 
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Delpy, L.P. and S.H. Gouchey. 1937. Biologie de Hyalomma dromedarii 
(Koch, 1844). Annals of Parasitology and Human Comp.  15:487-499. 

Despins, J.L. 1992. Effects of temperature and humidity on 
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Dermacentor (Anocentor) nitens. Journal  of  Medical Entomology 
29(2):332-337. 

 

Hagras, A.E. and G.M. Khalil. 1988. Effect of temperature on 
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Honzakova, E. 1971. Development of some tick species under standard 
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Hoogstraal, H. 1956. African Ixodidae. 1.Ticks of the Sudan. U.S. Naval 
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Hunter, W.D. and W.A. Hooker. 1907. Information concerning the 
North American fever tick with notes on other species. USDA 
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Latha, B.R , T.J. Harikrishnan, and D.J. Chella. 1998. Variation in the 
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Milne, A. 1950. The ecology of the sheep tick Ixodes ricinus L. 
Microhabitat economy of the adult tick.  Parasitology  40:14-34. 

Ouhelli, H. 1994. Comparative development of Hyalomma 
marginatum (Koch, 1844), H. detritum (Schulze, 1919), H. 
lusitanicum (Koch, 1844) and H. dromedarii (Koch, 1844) under 
laboratory conditions.  Acta Parasitologica  39(3):153-157.  

Steel, R.G. and J.H. Torrie. 1981. Principles and Procedures of 
Statistics.   McGraw Hill Book Company, New York .                                                    

Sunder, N., S. Balasundaram, and R. Anandan.  1999.  A note on the 
two host life cycle pattern of Hyalomma anatolicum anatolicum fed 
on calves. Cherion  28(1-2):45-47. 

 
  
Received  July 2001. 
Accepted  November 2002.