Study On The Development Process Of Horn Flies Serving As The Vectors Of Camel Parabronemosis

Camel parabronemosis is a parasitic nematodiasis which can bring great damages to the camel industry and its vectors are Haematobia irritans and Haematobia titillans. In order to ensure the development of Parabronema skrjabini in its vectors, the studies were carried out, including a laboratory method for the maintaining and feeding of Haematobia irritans and H. Titillans, the criteria for dividing the larval instars of horn flies H.irritans and H.titillans, the morphological characteristics of different stages of the two horn flies, and a rapid verification method of PCR-RFLP for the identification of the two horn flies had been researched in this study. The horn flies were acquired in fields, following by being taken back to laboratory to groped the method of laboratory artificial rearing, and the samples of different stages of the two horn flies were collected during the artificial rearing process; Three morphological variables, i.e., the body length, and the length and width of pharyngeal sclerite of these larval samples, were measured, and the relationship between the measured index and the larval instars were analyzed to determine which index could be the best criteria of instar division; These samples of different stages of the two horn flies were observed detailedly, and the morphological characteristics had been recorded and described, and the differences between the two horn flies were compared; Besides, a method for classficating the two horn flies was established by applying PCR-RFLP. The results were as follows:1) In summer, the average development time from egg of the two horn flies to adult was 11 days that was reared under the natural temperature. Egg hatching occured after 24-28 hours and the larvae pass through three instar stages, after which they form pupae underneath the manure at days 4～5 days. The adults emerge 5～8 days later depending upon environmental temperature. The average emergence rate was 16.8%, but the passage of the two horn flies was failed. Sepsis cynipsea and Macrocheles sp., two insects which perhaps effect the growth and development of the two horn flies, had been found during the duration of rearing the two horn flies in the laboratory.2) The larvae of H. irritans and H. titillans can be divided into three instars. Pharyngeal sclerite was the characteristic structure of the larvae of the two horn flies, and the variables of the larvae of the two species in different ages showed the same growth pattern with the increase of larval instars. The length of pharyngeal sclerite was the best morphological variable for separating the larvae of the two horn flies, while the width of pharyngeal sclerite can be used as an assistant variable for the division of the larval instars. However, there is an overlap in the variation range of body length between the adjacent larval instars of the two horn flies, so body length can not be used to separate the instars accurately.3) The two horn flies in different ages can be distinguished by the difference morphological characteristics except 1 st instar larvae.4) The restriction endonuclease Avr Ⅱ could be used to classified the two horn flies rapidly and correctly, and the established method was not affected by the sample status and individuals.All in all, the study had filled up the blank of the above research about the horn fly at home and abroad, which will lay the foundation for the development of nematode Parabronema skrjabini in its vectors, and the development of efficient control measures of camel parabronemosis.