Two new species
of chigger mites (Acari: Trombiculidae) close to Neotrombicula minuta,
application of nonlinear multivariate statistics
Acarina. Russian Journal of
Acarology, 16 (1): 21-29 (2008).
S U M M A R Y
Two new species of chigger mites, Neotrombicula
urartensis sp. n. from rodents and birds and N.
kubanensis sp. n. from rodents, are described from Caucasus.
Neotrombicula urartensis sp. n.
differs from N. scrupulosa Kudryashova, 1993 in
having much more numerous ventral and caudal idiosomal setae (larger
VC, VS, and NDV), lesser number of dorsal idiosomal setae in rows 1—4 (D1-4),
lesser m-t, and longer AM. There are usually 6 setae in 1st
row (13 of 17 specimens measured), while N. scrupulosa
has more frequently 7—11 setae in 1st row (only
28 specimens of 244, i.e. 11.5%, have 6 setae in 1st
row). This material was previously identified as N. corvi
Kolebinova, 1971 (Stekolnikov, 1995), but according to new data N.
corvi is rather similar to N. scrupulosa.
N. kubanensis sp. n. clearly
differs from all other species of the minuta group
in having much longer AM reaching posterior scutal margin (AM = 45—49
versus 25—44). The new species resembles N. agriotricha
Stekolnikov, 1994 in having long barbs on scutal and idiosomal setae
and similar arrangement of dorsal idiosomal setae, but differs from it
(except for the longer AM) in having a nude lateral palpal tibial seta
versus branched, smaller scutum (AW = 64—68, PW = 81—86, PSB = 22—26,
SD = 46—55, AP = 22—26, versus 68—71, 86—92, 27—32, 54—60, and 27—31,
respectively), the much shorter legs (Ip = 702—776 and TaIII = 58—66
versus 844—900 and 76—83), and the lesser number of idiosomal setae (VS
= 21—29 and NDV = 47—62 versus 28—33 and 59—67).
Morphological discontinuity of Neotrombicula
urartensis and N. scrupulosa was
demonstrated using logistic regression analysis. Logistic regression
analysis yielded the following diagnostic equation:
P(N. urartensis) = Exp(–56.237
+ 1.268*VC)/(1 + Exp(–56.237 + 1.268*VC)).
If P > 0.5, the new specimen should be
identified as N. urartensis, otherwise it is
predicted to be N. scrupulosa. Solution of this
equation give boundary value of VC between 44 and 45. Thus, according
to the obtained diagnostic rule, N. urartensis
should have VC = 45 (P = 0.69) or more, while in N. scrupulosa
VC = 44 (P = 0.39) or less.