224
paratypes 3 dd' 10.3 (9.0-11.4) mm, 3998.2 (7.98.7)mm.
Streptocephalus dorothae Mackin, 1942
Material examined. DB 191 Navajo Co., Arizona,
USA 12 dd 12.5 (11.4-13.3)mm, 11<;;x.¥11.8 (10.113.5) mm; HMPS VIIIa-2790 Kirkland let. Yavapai
Co., Arizona, USA 4 dd 2l.3 (19.2-22.7) mm, 499
21.3 (20.3-22.0)mm; UJED 183 LaPaz, Baja California Sur, Mexico 2 d'd 25.0,26.0 mm; USNM 184652
Flagstag, Coconino Co., Arizona, USA 5 d'd 14.3
(12.5-15.5) mm, 59913.9 (12.7-15.3) mm.
Streptocephalus linderi Moore, 1966
Material examined. DB 087 SW Sabinas, Coahuila,
Mexic03 dd' 10.3(10.1-1O.5)mm,3<;;x.¥1O.5(1O.011.0) mm; HMPS VIIIa2793 Sabinas, Coahuila, Mexico 5 dd 10.2 (9.8-10.7) mm, 59910.1 (9.4-1l.3)
mm; USNM 120449 W Ozona, Crocket Co., Texas,
USA 5 dd 14.3 (13.0-15.0) mm, 59913.1 (12.014.0) mm.
Streptocephalus mackini Moore, 1966
Material examined. ENEP 91.04. Soianiquilpan,
Estado de Mexico, Mexico 10 dd 13.9 (12.9-15.1)
mm; HMPS VIIIa-4473 Tepezala, Aguascalientes,
Mexico 4 dd' 14.9 (13.7-16.4) mm; HMPS VIIIa4474 Calvillo, Aguascalientes, Mexico 3 dd 17.5
(16.8-17.9) mm, 59917.7 (16.8-18.7) mm; UG 94
Culberson Co., Texas, USA 7 dd 15.7 (14.4-17.0)
mm, 49915.2 (14.0-16.0) mm; UJED 180 Culiacan,
Sinaloa, Mexico 12 dd 26.5 (24.8-28.7) mm, 15
9928.3 (28.0-29.5) mm; UJED 192 EI Sueco, Chihuahua, Mexico 10 dd' 28.9 (25.7-32.2) mm, 899
33.3 (31.0-35.0) mm; UJED 243 Torreon, Coahuila,
Mexico 12 dd 12.3 (11.1-14.0) mm; UJED 290
Aguascalientes, Aguascalientes, Mexico 12 dd 13.4
(12.0-14.4) mm, 109912.9 (12.4-14.0) mm.
Streptocephalus moorei Belk, 1973
Material examined. DB 62 Jimenez, Chihuahua,
Mexico, paratypes 2 dd 14.4, 15.0 mm, 29912.0,
12.2mm.
Streptocephalus texanus Packard, 1871
Material examined. HMPS VIIIa-2792 Paulden,
Yavapai Co., Arizona, USA 4 dd 21.9 (21.1-22.7)
mm, 49922.2 (20.0-23.7) mm; UG 95 Gillespie Co.,
Texas, USA 8 dd 10.4 (9.2--10.9) mm, 99910.8
(10.5-11.2) mm.
Streptocephalus sp. D
Material examined. DB 725 Ciudad del Maiz, San
Luis Potosi, Mexico 12 dd 15.4 (12.9-17.2) mm, 11
9914.5 (12.6-16.1) mm.
Discussion
Among the calculated ratios, the most informative ones
were pd/sl, pdlbj, and aj/pd. The ratios pd/sl (Fig. 9 A)
and ajlpd are useful to discriminate the species groups
with long peduncles from those with intermediate and
short peduncles. A discrimination between intermediate and short peduncles is achieved by using the two
ratios pd/sl and pd/bj. A short peduncle is typically shorter than the basal joint, while an intermediate
one is about as long as the basal joint. In contrast, no
apparent groups were found using the ratios bjlsl, aj/sl
(Fig. 9 B, C), and (bj + pd)/sl. We investigated the
relationship between the standard length and the ratios
pd/sl, pd/bj and aj/pd, by comparing the individual
values of a number of specimens of the same species
but of different sizes (collected at different localities
and dates) (Figs 10, 11). The results demonstrate that
the type of peduncle is the same at any size of the
adult stage. Therefore, the set of ratios pd/sl, pdlbj,
and aj/pd is a reliable discriminating criterion for the
different types of peduncles. It is important to point out
that the determination of the type of peduncle requires
fully grown adult males in good condition of preservation. We found, for instance, that fully grown males of
S. dichotomus have a long peduncle, while conspecific sub adults showed ratios typical of an intermediate
peduncle.
Regarding the rotation of the hand (shown by all
species with a long peduncle, but less pronounced in
species of the cafer group with intermediate peduncle),
it is clear that a structural modification has occurred,
and that this is not an artifact of fixation or preservation.
This is supported by the constancy of this character in
the species of which material was fixed in both formalin
and alcohol. It is required, however, that the antennae
be in the normal, retracted position. Thus, for example,
from material fixed in formalin (UG 227), we identified
paratypes 3 dd' 10.3 (9.0-11.4) mm, 3998.2 (7.98.7)mm.
Streptocephalus dorothae Mackin, 1942
Material examined. DB 191 Navajo Co., Arizona,
USA 12 dd 12.5 (11.4-13.3)mm, 11<;;x.¥11.8 (10.113.5) mm; HMPS VIIIa-2790 Kirkland let. Yavapai
Co., Arizona, USA 4 dd 2l.3 (19.2-22.7) mm, 499
21.3 (20.3-22.0)mm; UJED 183 LaPaz, Baja California Sur, Mexico 2 d'd 25.0,26.0 mm; USNM 184652
Flagstag, Coconino Co., Arizona, USA 5 d'd 14.3
(12.5-15.5) mm, 59913.9 (12.7-15.3) mm.
Streptocephalus linderi Moore, 1966
Material examined. DB 087 SW Sabinas, Coahuila,
Mexic03 dd' 10.3(10.1-1O.5)mm,3<;;x.¥1O.5(1O.011.0) mm; HMPS VIIIa2793 Sabinas, Coahuila, Mexico 5 dd 10.2 (9.8-10.7) mm, 59910.1 (9.4-1l.3)
mm; USNM 120449 W Ozona, Crocket Co., Texas,
USA 5 dd 14.3 (13.0-15.0) mm, 59913.1 (12.014.0) mm.
Streptocephalus mackini Moore, 1966
Material examined. ENEP 91.04. Soianiquilpan,
Estado de Mexico, Mexico 10 dd 13.9 (12.9-15.1)
mm; HMPS VIIIa-4473 Tepezala, Aguascalientes,
Mexico 4 dd' 14.9 (13.7-16.4) mm; HMPS VIIIa4474 Calvillo, Aguascalientes, Mexico 3 dd 17.5
(16.8-17.9) mm, 59917.7 (16.8-18.7) mm; UG 94
Culberson Co., Texas, USA 7 dd 15.7 (14.4-17.0)
mm, 49915.2 (14.0-16.0) mm; UJED 180 Culiacan,
Sinaloa, Mexico 12 dd 26.5 (24.8-28.7) mm, 15
9928.3 (28.0-29.5) mm; UJED 192 EI Sueco, Chihuahua, Mexico 10 dd' 28.9 (25.7-32.2) mm, 899
33.3 (31.0-35.0) mm; UJED 243 Torreon, Coahuila,
Mexico 12 dd 12.3 (11.1-14.0) mm; UJED 290
Aguascalientes, Aguascalientes, Mexico 12 dd 13.4
(12.0-14.4) mm, 109912.9 (12.4-14.0) mm.
Streptocephalus moorei Belk, 1973
Material examined. DB 62 Jimenez, Chihuahua,
Mexico, paratypes 2 dd 14.4, 15.0 mm, 29912.0,
12.2mm.
Streptocephalus texanus Packard, 1871
Material examined. HMPS VIIIa-2792 Paulden,
Yavapai Co., Arizona, USA 4 dd 21.9 (21.1-22.7)
mm, 49922.2 (20.0-23.7) mm; UG 95 Gillespie Co.,
Texas, USA 8 dd 10.4 (9.2--10.9) mm, 99910.8
(10.5-11.2) mm.
Streptocephalus sp. D
Material examined. DB 725 Ciudad del Maiz, San
Luis Potosi, Mexico 12 dd 15.4 (12.9-17.2) mm, 11
9914.5 (12.6-16.1) mm.
Discussion
Among the calculated ratios, the most informative ones
were pd/sl, pdlbj, and aj/pd. The ratios pd/sl (Fig. 9 A)
and ajlpd are useful to discriminate the species groups
with long peduncles from those with intermediate and
short peduncles. A discrimination between intermediate and short peduncles is achieved by using the two
ratios pd/sl and pd/bj. A short peduncle is typically shorter than the basal joint, while an intermediate
one is about as long as the basal joint. In contrast, no
apparent groups were found using the ratios bjlsl, aj/sl
(Fig. 9 B, C), and (bj + pd)/sl. We investigated the
relationship between the standard length and the ratios
pd/sl, pd/bj and aj/pd, by comparing the individual
values of a number of specimens of the same species
but of different sizes (collected at different localities
and dates) (Figs 10, 11). The results demonstrate that
the type of peduncle is the same at any size of the
adult stage. Therefore, the set of ratios pd/sl, pdlbj,
and aj/pd is a reliable discriminating criterion for the
different types of peduncles. It is important to point out
that the determination of the type of peduncle requires
fully grown adult males in good condition of preservation. We found, for instance, that fully grown males of
S. dichotomus have a long peduncle, while conspecific sub adults showed ratios typical of an intermediate
peduncle.
Regarding the rotation of the hand (shown by all
species with a long peduncle, but less pronounced in
species of the cafer group with intermediate peduncle),
it is clear that a structural modification has occurred,
and that this is not an artifact of fixation or preservation.
This is supported by the constancy of this character in
the species of which material was fixed in both formalin
and alcohol. It is required, however, that the antennae
be in the normal, retracted position. Thus, for example,
from material fixed in formalin (UG 227), we identified