Key to species of the rectus group of Conchopus Takagi (males)

1. Middle section of M1+2 not thickened (Figs. 18 a,b)........................................................... 2

- Middle section of M1+2 thickened (Figs. 18 c–f)............................................................. 4

2. Middle tarsomere 1without remarkably long anterior fine setae (Fig. 19 a)......................................... 3

- Middle tarsomere 1with remarkably long fine anterior setae (Japan, China).............................. rectus Takagi

3. Basal lobe of fore tarsomere 1 with 3–4 rather long marginal setulae (Figs. 1 a,b); ventral lobe as long as cercus, distinctly extended ventrally beyond tip of cercus (Fig. 3 a) (Hawai‘i, Maui, Lāna‘i, Moloka‘i)................ acrosticalis (Parent)

- Basal lobe of fore tarsomere 1 with 4–5 rather short marginal setulae (Figs. 4 a,b); ventral lobe shorter than 2/3 length of cercus (Figs. 6 a,b) (Hawai‘i, Maui, O‘ahu, Lisianski).................................................. ciliatus sp. nov.

4. Middle tibia and tarsomere 1 with remarkably long anterior setae (Fig. 19 b)...................................... 5

- Middle tibia and tarsomere 1 without remarkably long anterior setae............................................ 6

5. Ventral bristle of fore tarsomere 1 weak (Figs. 7 a,b) (Kaua‘i)................................... crassinervis sp. nov.

- Ventral bristle of fore tarsomere 1 strong (Japan, N. America, Peru)............................ borealis Takagi, 1965

6. Fore tarsomere 1 without strong ventral bristle (Japan)..................................... sikokianus Takagi, 1965

- Fore tarsomere 1 with strong ventral bristle................................................................ 7

7. Ventral bristle of fore tarsomere 1situated 1/3 of way from base (Figs. 13 a,b) (Kaua‘i, Nihoa).......... menehune sp. nov.

- Ventral bristle of fore tarsomere 1 situated halfway from base................................................. 8

8. Fore tarsomere 1 with raised keel ciliated with 2–4 setulae between basal lobe and ventral bristle (Figs. 15 a,b) (Hawai‘i, O‘ahu, Kaua‘i, Wake)................................................................... .. pacificus sp. nov.

- Fore tarsomere 1 without raised keel between basal lobe and ventral bristle (Figs. 10 a,b)............................ 9

9. Discal crossvein strongly oblique (Fig. 18 d) (Hawai‘i, Maui, Lāna‘i, Moloka‘i, O‘ahu, French Frigate Shoals)................................................................................................... minutus sp. nov.

- Discal crossvein slightly oblique........................................................................ 10

10. First flagellomere 1.5 times as long as wide, fore tarsomere 2 with two or more erect anterodorsal bristles (Japan, Taiwan).................................................................................... taivanensis Takagi, 1967

- First flagellomere 2.0 times as long as wide, fore tarsomere 2 with one erect anterodorsal bristle (Japan)...................................................................................................... pudicus Takagi, 1965