24 
Regeneration in Ticks 
15-20 minutes, and proceed with their metamorphosis after abandoning 
the host, consequently, when they are mutilated soon after feeding, they 
regenerate their mouthparts (and legs) better than do the larvae. After 
operations on larvae and first-stage nymphs regeneration takes place best in 
the hypostome, next in the chelicerae and least well in the palps. This order 
was reversed after similar opeiations on second-stage nymphs. The power 
to regenerate palps and chelicerae grows as the tick approaches maturity, 
but it remains fairly constant for the hypostome. Amputations made through 
the basis capituli usually render the tick incapable of feeding after it has 
moulted to the next stage, the mouthparts not having been adequately re¬ 
generated. In one case ( Argas 72), however, the amputation of the anterior 
part of the capitulum with its appendages in a second-stage nymph was 
followed by almost perfect regeneration of the part in the succeeding third- 
stage nymph. Where regeneration did not take place adequately after severer 
operations on the basis capituli, as exemplified in another case ( Argas 73), 
the mutilated tick lived on without its capitulum for four years without a 
meal. This experiment explains the origin of the anomalous ‘'headless 
female” of Ixodes ricinus, referred to and figured by Wheler 1 , which lived 
four years and was lost. Lesser mutilations, i.e. those affecting the appendages 
only, are frequently followed by perfect regeneration if the injury is slight. 
Imperfectly regenerated parts are often capable of functioning so that the 
tick can feed. Such a tick, if not interfered with, will acquire perfectly normal 
mouthparts at the next moult. 
The immature stages of the Ixodid ticks A. hebraeum and H. aegyptium 
behave differently to Argas persicus when injured soon after abandoning the 
host, in that they possess much greater powers of regeneration. Basal or 
partial amputations of the hypostome and palps, or moderate mutilations of 
the chelicerae, are followed by perfect regeneration in most cases. 
The greater power of regeneration possessed by Ixodid ticks bears directly 
upon their parasitic habits. The slowly feeding larval stages of Argasids 
(A. persicus, A. vespertilionis, for example) possess relatively more dentate 
hypostomes than do the adults which are rapid feeders. With the exception 
of Haemaphysalis concinna (vide Brumpt’s observations recorded by me in 
Parasitology , vn. 434) all known Ixodids are slow feeders and an examina¬ 
tion of genera like Ixodes, Amblyomma and Hyalomma proves that their 
hypostomes are most efficient organs for anchoring the tick to the host. 
The accompanying illustrations (Figs. 5 and 6) of the capitulums of A. liebraeum 
and H. aegyptium females show that they possess long, highly dentate hypo¬ 
stomes broadening distally and liable to break where they narrow toward the 
base when violence is done to the tick that is fixed thereby to the skin. The 
examination of such Ixodid ticks collected in the field proves how frequently 
their long hypostomes get broken off near the base, and consequently how 
vital it is that they should be readily regenerated. Whilst a tick may save 
1 Wheler, E. G. (iii. 1906). British Ticks. Journ. of Agricult. Sci. i. p. 401, Plate X, fig. 38. 
