139 
PARTHENOGENESIS IN TICKS. 
(preliminary note.) 
By GEORGE H. F. NUTTALL, F.R.S. 
(From the Quick Laboratory, University of Cambridge.) 
Aragao (1912) has recently described a new species of tick which 
he raised through three complete generations upon cold-blooded animals, 
the natural hosts in Brazil. He gave the species the name Amblyomma 
agamum because reproduction occurred parthenogenetically, males not 
having as yet been observed. The tick, in common with most other 
Ixodidae, feeds upon three successive hosts in the larval, nymphal and 
adult stages; it may, however, undergo metamorphosis from larva to 
nymph upon the host. This observation of Aragao’s is the first of the 
kind, for parthenogenesis has not hitherto been observed in ticks. In 
the course of his raising experiments he obtained thousands of females 
which laid fertile eggs in the absence of males. 
On reading Aragao’s paper, it occui’red to me that it would be of 
interest to determine if parthenogenesis occurs in ticks where males are 
commonly encountered with females, the sexes being usually found in 
equal numbers upon the host. The experiment is being tried at present 
with several species, a positive result having been obtained, however, 
with Rhipicephalus bursa, a common sheep tick in parts of Southern 
Europe and Northern Africa. 
When males and females of this species are placed together upon 
sheep the replete fertilized females abandon the host after 4-12 days 
and lay 5000-7000 eggs. When we placed females alone upon a sheep 
they remained upon it for 25-3S days and abandoned the host without 
having fully gorged themselves with blood. Some of them began to 
oviposit after a normal interval of time and many of the eggs shrivelled 
up. The number of eggs laid per female is smaller (about 2000) than 
in females which have fed to repletion in the presence of males. 
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