New Neotropical and Nearctic species of water beetles in the genera Hydraena Kugelann and Ochthebius Leach, a key to North American genera and subgenera of the family, new distribution records, and a synopsis of ecology, behavior and morphology related to aquatic life (Coleoptera: Hydraenidae)
Author
Perkins, Philip D.
text
Zootaxa
2023
2023-11-07
5367
1
1
86
https://www.mapress.com/zt/article/download/zootaxa.5367.1.1/52225
journal article
10.11646/zootaxa.5367.1.1
1175-5334
10145106
5A1E5321-D2BA-4B92-BA23-A7C1CDBA5723
Ochthebius
(
Gymnochthebius
)
falli
(Perkins)
Species Status Reinstated
(
Figs. 34–36
)
Gymnochthebius falli
Perkins 1980: 281
Ochthebius
(
Gymnochthebius
)
fossatus
LeConte
;
Jäch 1994
(invalid synonymy)
The
following collection/deposition data include the first records for
Mexico
.
The
data also includes several first museum depositories for the species.
The
new records increase the number of identified specimens in museum collections from 40 to 60.
The
range of this species (
Fig. 36
) extends northward from
Oaxaca
,
Mexico
to
western Kansas
and
southern Idaho. The
one male
specimen known from the northernmost locality, Idaho, was collected in a thermal spring in 1957. The
two specimens
from one site in Arizona were collected in 1920. It is possible that the species has been extirpated from these localities. The records from
western Texas
were collected relatively recently, from 1991–2000
.
New
records:
Mexico
:
Estado de México
,
Aguascalientes
,
3–5.viii.1963
, leg.
P. J. Spangler
(10
NMNH
)
;
km 15
Almoloya-Apán
,
2.iii.1989
,
R. Arce
col. (3
IEXA
)
.
Oaxaca
,
3 km
E Santiago Yolomecatl
,
9.x.1990
, leg.
R. Baranowski
(1
LUM
)
;
U.S.A.
:
Texas
,
Brewster
,
Big Bend National Park
,
Buttrill Springs
,
17.vii.1991
, leg.
R. C. Vogtsberger
(2
TAMU
)
;
Stillwell
RV
Park
on hwy 2627,
4–5.vi.1994
, leg.
E. G. Riley
(3
TAMU
)
;
Presidio Co.
,
Drying Creek
,
12 mi.
N. Ruidosa Rd
2810,
4.v.2000
, leg.
G. L. Challet
(1
MCZ
)
.
Discussion.
When species are placed into synonymy it is contingent upon experienced taxonomists to clearly discuss and illustrate the characters that are known to be highly diagnostic in that taxon. In
Hydraenidae
the male genitalia are widely known as the most highly diagnostic character to use to differentiate species. For this reason,
Perkins (1980: 278)
illustrated the male genitalia of representatives of all forms that were placed into synonymy, including the junior synonyms of
H.
(
Gymnochthebius
)
fossatus
, including examples from
Brazil
, Florida,
Mexico
, and Texas.
Contrastingly,
Jäch (1994)
, when publishing a supposed synonymy, did not illustrate any male genitalia, and significantly did not discuss the marked differences in the male genitalia of
H.
(
Gymnochthebius
)
falli
and
H.
(
Gymnochthebius
)
fossatus
that were illustrated by
Perkins (1980: 278)
. He also did not examine the
holotype
of
H.
(
Gymnochthebius
)
falli
. These are significant omissions.
Even though the differences in the male genitalia of the two species were illustrated adequately by line drawings in
Perkins (1980)
, additional documentation, in the form of photographic images, is given herein, in order to make the differences abundantly clear to all students of the group.
Aedeagal characters differentiating the two species: (1) In
H.
(
G.
)
falli
(
Fig. 34
) the internal tubule is straight over the midlength, then has an abrupt bend in the distal ¼. In
H.
(
G.
)
fossatus
(
Fig. 35
) the internal tubule is arcuate for the entire length, without a bend in the distal ½. (2) The lumen aperture of
H.
(
G.
)
falli
has a more oval-elongate shape, whereas the aperture is as wide as long in
H.
(
G.
)
fossatus
. (3) The strongly sclerotized distal ends of the main-piece of
H.
(
G.
)
falli
are more narrowly separated than those of
H.
(
G.
)
fossatus
. (4) The main-piece, in dorsal or ventral views, compared to the length of the aedeagus, is wider in
H.
(
G.
)
falli
(l/w ca. 3.9) than in
H.
(
G.
)
fossatus
(l/w ca. 5.1). (5) The ratio of the width of the lumen opening and the maximum width of the main-piece is about 1:
5.5 in
H.
(
G.
)
falli
vs. about 1:
2.6 in
H.
(
G.
)
fossatus
.
The shapes and sizes of these structures are all integrated by behavior: the aedeagal tube is everted during copulation (
Perkins 1980: 20
). These significant differences are not easily overlooked.
The specimens used to illustrate these structural differences were collected at the same locality in
Mexico
, during the same collecting event. Although the aedeagi used to illustrate these structures are approximately the same length, the adults differ notably in size, the specimen of
H.
(
G.
)
falli
being larger (1.89 vs.
1.65 mm
total length). There is considerable body size variation of
H.
(
G.
)
fossatus
over its extensive geographical range (see
Perkins 1980
). Specimens of
H.
(
G.
)
falli
average larger than the upper end of this size variation. Another difference in the figures is that the specimen of
H.
(
G.
)
fossatus
is teneral. This of course has no bearing on the decision that the specimens represent two species.