Immatures of Palaearctic species of the weevil genus Tychius (Coleoptera, Curculionidae): new descriptions and new bionomic data with an evaluation of their value in a phylogenetic reconstruction of the genus
Author
Skuhrovec, Jiří
Author
Gosik, Rafał
Author
Caldara, Roberto
text
Zootaxa
2014
2014-07-23
3839
1
1
83
journal article
5426
10.11646/zootaxa.3839.1.1
6d32f9c2-3094-425b-bb7e-9c6e0517d4fd
1175-5326
4927721
AA7FEED5-5C1F-48D0-A172-5C25C4001DF3
Tychius
(s. str.)
brisouti
Tournier, 1874
Caldara 1990: 203
;
1995b: 610
.
Material examined
.
29 larvae
from pods of
Astragalus monspessulanus
L. collected
29.v.2008
at
Castellar
near
Menton
,
Alpes-Maritimes
(southern
France
), leg.
R
.
Caldara
, and
5 pupae
obtained from larvae collected similarly to the others, all determined by association with reared adults.
Differential diagnosis.
See
Tables 2
and
3
.
Description of mature larva.
COLORATION. Head brown to dark brown. All thoracic and abdominal segments light yellow.
HEAD CAPSULE AND MOUTH PARTS. Head width:
0.68–0.75 mm
(see
Table. 1
). Endocarinal line present, exceeding middle of frons.
Des
1
located almost in central parts of epicarnium;
des
2
located very near frontal suture, near
des
3
;
des
3
located along frontal suture;
des
4
absent;
des
5
located anterolaterally;
des
2
5 times shorter than
des
3
and
des
5
(
Fig. 47
).
Fs
1
and
fs
2
absent;
fs
3
short, located medially;
fs
4
located anteromedially (along epistoma);
fs
5
located anterolaterally (along epistoma), 4 times longer than
fs
3
(
Fig. 47
).
Les
distinctly shorter than
des
3
.
Ves
short. Post-epicranial area with group of 4 minute
pes
. Antennal segment membranous, bearing conical sensorium and 2 finger-like, sensilla (
Fig. 50
).
Labrum (
Fig. 51
) approximately 3 times as wide as long;
lms
1
slightly longer than
lms
2
and
lms
3
; anterior margin rounded. Clypeus (
Fig. 51
) 3.9 times as wide as long; without setae; anterior margin slightly rounded inside. Epipharynx (
Fig. 52
) with 2 pairs of
als
, almost of equal length; with 2 pairs of short
ams
,
ams
2
distinctly shorter than
ams
1
; with 3 relatively short and finger-like
mes
; labral rods relatively long, elongate, slightly converging posteriorly. Mandibles (
Fig. 49
) with 2 short
mds
, almost of equal length. Maxilla (
Fig. 48
): stipes with 1
stps
, 2
pfs
of equal length, and 1
mbs
, distinctly shorter than
pfs
, and 1 sensillum; with 4 straight
dms
, different in length; with 4
vms
, short and almost of equal length. Maxillary palpi: length ratio of basal and distal palpomeres 1:1.25; basal palpomera with 1 short
mpxs
; distal palpomera with group of 3–4 conical, cuticular apical processes. Prementum (
Fig. 48
) heart-shaped, with 1
prms
; margin of ligula slightly rounded; ligula with 1
lig
; premental sclerite distinct. Postmentum (
Fig. 48
) with 3 pairs of
pms
, different in length.
THORAX AND ABDOMEN. Body length
4.3–6.6 mm
(see
Table. 1
), elongate. Abdominal segments I–VI almost equal in length (
Fig. 53
). Spiracles on abdomen in anteromedian parts of segments (abdominal seg. I–VIII).
Chaetotaxy of body rather reduced. Setae moderately long or short, and light yellow.
Thorax.
Prothorax (
Fig. 54
) with 7
prn
, 5 macro- and 2 microsetae; 2 moderately long
ps
of same length; 1
eus
. Meso- and metathorax (
Fig. 54
) with 1
prs
; 3
pds
, different in length; alar area with 1 very short
as
; 1 very short
ss
; 1
eps
; 1
ps
; and 1 short
eus
. Each pedal area of thoracic segments well-separated and with 2 long and 2 short
pda
.
Abdomen.
Abdominal segments I–VII (
Fig. 55
) with 1
prs
; 3
pds
different in length; 2
ss
of different length; 2
eps
of different length; 2
ps
; 1
lsts
; and 2 short
eus
. Abdominal segment VIII (
Fig. 56
) with 1
prs
; 2
pds
; 1
ss
; 2
eps
of different length; 2
ps
; 1
lsts
; and 2 short
eus
. Abdominal segment IX (
Fig. 56
) with 2
ds
of different length; 2
ps
; and 1
sts
. Each anal lobe on abdominal segment X (
Fig. 56
) with 1 very short, feebly visible seta.
Description of pupa.
COLORATION. Body salmon.
MORPHOLOGY (
Figs. 57–59
). Body length
3.2–3.8 mm
; widest part
1.3–1.9 mm
(see
Table. 1
). Body rather stocky. Rostrum long, approximately 6 times as long as wide, reaching mesocoxae. Pronotum 1.7 times as wide as long.
CHAETOTAXY (
Figs. 57–59
). Setae distinct, moderately long, unequal in length, light brown; on pronotum and head placed on small protuberances. Head capsule including 2
vs
, 1
os
, and 1
pas
. Rostrum with 1
rs
located medially.
Vs
1
and
os
as long as setae on pronotum, distinctly longer than
vs
2
,
pas
and
rs
. Pronotum with 2
as
, 2
ls
, 2
ds
, and 1
pls
;
ds
distinctly smaller than other setae on pronotum. Dorsal part of meso- and metathorax with 1 seta. Each apex of femora with 1
fes
. Setae on abdominal segments I–VIII placed medially and laterally; all abdominal setae located on small, conical protuberances. Pseudocerci slender, slightly curved inside.
Biological observations.
Some adults were collected at the end of April when the plants were flowering and there were no mature pods. At the end of May the pods were mature in most plants and the adults were lacking. About 15 % of collected pods were infested by larvae of
T. brisouti
. Pupation was observed 10 days after the introduction of the larvae in the soil. Adults were observed in the cells 10 days later. After 30 days they had not left the cell and were manually removed.
Remarks.
Tychius brisouti
is a rare monophagous species on
Astragalus monspessulanus
and only known from a few localities of south-eastern
Spain
, southern
France
and north western
Italy
. However the observation about the collecting methods for
T. alpinus
can be applied also for this species.