1. Basal article of metatarsus longer than two following articles combined......2
– Basal article of metatarsus at most as long as two following articles combined ( Fig. 1)........................................................................................................3
2. Antennal articles 8-10 strongly transverse (Figs 27 a, b); median lobe of aedeagus with narrowly triangular apical part in lateral view (Fig. 91), and bulbus with two lateral projections in dorsal view (Fig. 92); spermatheca with capsule pitcher-shaped (Fig. 96); female sternite 8 rounded apically (Fig. 98) .................................................................................... G. brevicornis Casey
– Antennal articles 8-10 quadrate or slightly elongate (Figs 32 a, b); median lobe of aedeagus with broadly triangular apical part in lateral view (Fig. 130); spermatheca C-shaped, capsule mushroom-formed (Fig. 136); female sternite 8 emarginate apically (Fig. 138)...................................... G. uteana (Casey)
3. Body broad and robust ( Fig. 8), pronotum at base about as broad as elytra ( Fig. 8), abdomen swollen medially and at base as broad as elytra ( Fig. 8); median lobe of aedeagus and spermatheca as illustrated ( Figs 83, 84, 88) ..... ............................................................................... G. groenlandica Lohse
– Body narrow and less robust ( Figs 3, 5, 6, 9, 14, 15), pronotum at base narrower than elytra, abdomen subparallel and at base narrower than elytra ( Figs 3, 7, 9 -15); genitalia differently shaped.......................................................4
4. Elytra at suture approximately as long as pronotum ( Figs 3, 6, 7, 10, 15-19) ................................................................................................................... 5
– Elytra at suture distinctly longer than pronotum ( Figs 4, 5, 11 -13, 20).... 13
5. Antennal articles 7-10 strongly transverse (Figs 21 a, b); median lobe of aedeagus and spermatheca as illustrated ( Figs 39, 40, 41, 45) .............. G. ashei sp. nov.
– Antennal articles 7-10 elongate, subquadrate or slightly transverse (Figs 23-25 a, b, 28 a, b, 31 b, 33-37 a, b); genitalia differently shaped ( Figs 75, 76, 80, 99-101, 105, 139-141, 145, 148, 149, 153, 156, 157, 161, 164, 165, 169, 172-174, 178).....6
6. Antennal articles 7-10 slightly transverse (Figs 24 a, b, 25 a, b, 33 a, b); female sternite 8 without deep median emargination ( Figs 74, 82, 147) ........ 7
– Antennal articles 7-10 elongate or subquadrate (Figs 28 a, b, 34-37 a, b); female sternite 8, except for G. caerulea, with deep apical emargination (Figs 107, 155, 163, 171, 180)............................................................................ 9
7. Body length 3.0-3.4 mm; median lobe of the aedeagus with apical part narrowly produced ( Fig. 66); spermatheca with capsule funnel-shaped and as wide as long ( Fig. 72).................................................. G. sellmani Brundin
– Body length 2.5-3.0 mm; median lobe of aedeagus and spermatheca differently shaped ( Figs 75, 76, 80, 139-141, 145).............................................. 8
8. Body length 2.5-2.7 mm; male tergite 8 with four apical dents on apical margin ( Fig. 78); spermatheca with capsule funnel-shaped ( Fig. 80); median lobe of aedeagus with apical part narrowly triangular with sinuate margins ( Fig. 75)......................................................................... G. dentata sp. nov.
– Body length 2.7-3.0 mm; male tergite 8 without teeth and with minute median emargination on apical margin (Fig. 143); spermatheca with apical part of capsule approximately spherical (Fig. 145); median lobe of aedeagus with apical part moderately narrowly triangular, narrowly bottle-shaped (Fig. 139)...................................................... G. carbonaria (Mannerheim)
9. Integument moderately glossy with minute pubescence (Figs 18, 19); basal three tergal impressions virtually impunctate except for the margins of tergites ( Figs 1, 18, 19); body length 2.4-3.0 mm; genitalia as in Figs 164, 165, 169, 172-174, 178 ...........................................................................10
– Integument strongly glossy with pubescence moderately long (Figs 10, 16, 17); basal three tergal impressions with dispersed punctation (Figs 10, 16, 17); body length 2.7-3.5 mm; genitalia as illustrated (Figs 99-101, 105, 148, 149, 153, 156, 157, 161)..........................................................................11
10. Pronotum and abdomen at base distinctly narrower than elytra (Fig. 18); first three visible tergal impressions lacking coarse punctation except for the posterior margin ( Fig. 1); median lobe of aedeagus with tubus swollen laterally (Fig. 164), spermatheca club-shaped (Fig. 169) ......... G. nigrella (LeConte)
– Pronotum and abdomen at base slightly narrower than elytra (Fig. 19); first three visible tergal impressions with dispersed coarse punctation; genital structures differently shaped (Figs 172-174, 178) ..... G. saccharina sp. nov.
11. Body length 3.0-3.5 mm; genitalia as illustrated (Figs 99-101, 105) ............ ................................................................................ G. caerulea (Sahlberg)
– Body length 2.5-3.0 mm; genitalia differently shaped (Figs 148, 149, 153, 156, 157, 161).......................................................................................... 12
12. Median lobe of aedeagus with moderately broad and slightly produced ventrally apical part (Fig. 148); spermatheca with thin stem (Fig. 153); western Canada............................................................................. G. helenae Casey
– Median lobe of aedeagus narrowly triangular and strongly produced ventrally (Fig. 156); spermatheca with moderately wide stem (Fig. 161); eastern Canada..................................................................... G. canadensis sp. nov.
13. Antennal articles 7-10 strongly elongate (Figs 23 a, b); median lobe of aedeagus and spermatheca as illustrated ( Figs 57-59, 63)....... G. atrolucens Casey
– Antennal articles 7-10 subquadrate to transverse (Figs 22 a, b, 29-31 a, b, 38 a, b); genital structures differently shaped ( Figs 48-50, 54, 108-110, 114, 117, 118, 122, 127-129, 181-182, 186, 187) ...........................................14
14. Abdomen broad, at base approximately as broad as elytra ( Figs 11, 13); genital structures as illustrated (Figs 108-110, 114, 127-129)..........................15
– Abdomen moderately broad, at base distinctly narrower than elytra ( Figs 4, 12, 20); genital structures differently shaped ( Figs 48-50, 54, 117, 118, 122, 181, 182, 186, 187) .................................................................................16
15. Antennal articles 7-10 subquadrate (Fig. 31 b); spermatheca C-shaped (Figs 127-129) ..................................................................... G. manitobae Casey
– Antennal articles 7-10 transverse (Figs 29 a, b); spermatheca S-shaped (Fig. 114).......................................................................... G. lohsei sp. nov.
16. Pronotum almost as wide as elytra (Fig. 20); punctures in abdominal impressions very coarse (Fig. 20); abdomen strongly narrowed at base (Fig. 20); genital structures as illustrated (Figs 181, 182, 186, 187).............................. ....................................................................................... G. minuta sp. nov.
– Pronotum distinctly narrower than elytra ( Figs 4, 12); punctures in abdominal impressions fine or moderately coarse ( Figs 4, 12); genital structures differently shaped ( Figs 48-50, 54, 117, 118, 122)........................................17
17. Body small, length 2.7-3.0 mm (Fig. 12); median lobe of aedeagus with apical part narrowly produced ventrally (Fig. 117); spermatheca C-shaped, tubular (Fig. 122).................................................. G. crebrepunctata (Casey)
– Body large, length 3.2-3.6 mm ( Fig. 4); median lobe of aedeagus with apical part broadly triangular in lateral view ( Fig. 48); spermatheca with funnel-shaped capsule and thin and sinuate stem ( Fig. 54) ...................... ........................................................................................... G. brincki Palm