variance of chaetotactic characters in the chigger mite genus
19-26 (2001) (In Russian, English summary).
S U M M A R Y
Numbers of scutal, coxal and sternal setae
were counted in 1393 specimens of 5
Hirsutiella species. All observed
chaetotactic anomalies were classified into 3 groups: 1) "rare"
anomalies, such as absence of one AL, AM, coxal or sternal setae,
presence of additional AL, AM, coxal or anterior sternal setae; 2)
presence of 1—2 post-posterolateral scutal setae (PPL); 3) presence of
additional 1—3 posterior sternal setae.
"Rare" anomalies were found in 2.8% of the
specimens examined. They were observed usually in northern or alpine
populations. Obviously, it is an effect of more frequent ontogenetic
failures in rigorous climate conditions being out of optimum for
The quota of the individuals with PPL in a
set of H. steineri samples varied from 16 to 74%,
while in the other samples of this species the presence of the single
(and not more) PPL were found very seldom, as well as in the other
species examined. In the similar way, the additional posterior sternal
setae were found with the frequency up to 100% in the some samples of
H. steineri, H. hexasternalis and
H. alpina, but in other ones they
were present only in few specimens. Since in a series of cases the
ratio of the number of specimens with PPL to the number of specimens
without PPL, as well as the ratio of the number of specimens with
fSt=2.4 to the number of specimens with fSt=2.2 is almost equal to 2,
one can suppose that the variance of this characters has a genetic
All samples having a high frequency of the
PPL appearance or the appearance of additional posterior sternal setae
were collected in the alpine zone. It is an evident example of the
ecogeographical rules, which were reported previously by the author for
the quantitative characters in species of the genera
Neotrombicula (Stekolnikov, 1996,
1998, 1999) and Hirsutiella (Stekolnikov, 2000).
It is possible that the PPL appearance is caused by the higher humidity
of the climate, and the appearance of additional posterior sternal
setae — by the low temperature. It is supported by the fact that the
samples with high frequency of individuals having PPL are specific to
damp areas of Western Caucasus, while the populations with high
frequency of additional posterior sternal setae appear to be
characteristic for regions with more dry climate (Daghestan, Turkey,
Chelyabinsk Oblast of Russia).
The fact, that in some populations of H.
steineri, the individuals having PPL are prevalent, can
serve as a
serious argument for the abolishment of the genera
Hoffmannina Brennan et Jones,
1959 and Aboriginesia Kudryashova, 1993
distinguished from related groups only by the presence of these setae.