Skusella, Freeman. There, 1961

Cranston, Peter S. & Tang, Hongqu, 2018, Skusella Freeman (Diptera: Chironomidae): new species, immature stages from Africa, Asia and Australia, and expanded distributions, Zootaxa 4450 (1), pp. 41-65 : 57-61

Skusella sp. ‘Opi’

( Fig. 7C, H )

Material examined. NIGERIA, Anambra State, 2L (3rd i., 4th i), Opi Lake ‘A’ [= Ogelube Lake ], 6°45'0"N 7°29'30"E , 1.iii.1977 (Hare) ( NHM); same except 1L (2 i), Opi Lake ‘D’ , 15.v.1980.

Description. Larva 4i (n = 1). Head pale yellow with slightly darker golden-brown occipital margin, mandibles and mentum. Body length (extended exuviae) c. 10 mm, head capsule 500 µm, postmentum 150 µm. Antenna ( Fig. 7C ) segment lengths 115: 18: 45: 30: 10, 5; AR 1.06. Lauterborn organs 10 long; blade c. 60 long, extending to mid-segment 3. Labroepipharyngeal region as in S. subvittata, Premandible 65 long. Mandible 105. Mentum ( Fig. 7H ) 90 wide; ventromental plates 100 wide, separated medially by 50, VmPR 2.2.

Abdomen. Anterior parapod claws mid-yellow, simple, narrow, gently curved. Procercus pale, squat, 20 wide, 12 high, bearing 2 fine lateral seta, respectively 15 and 25 long; apically with 5 pale yellow setae 250–300 long. Posterior parapod claws pale yellow, simple, finely curved.

Larva 3i (n = 1) Head pale. Head capsule 250, submentum 105. Antenna 55, 8, 27, 17, 7, 4; A.R. 0.9. Premandible 65. Mandible 70. Mentum 53 wide; ventromental plates 65, separated medially by 45, VmPR 2.6.

Larva 2i (n = 1). Head pale, body red (stained?). Body length 1.7mm. Head capsule 150, submentum 60. Antenna 30, 6, 15, 9, 4.5, 3; A.R. 0.9. Premandible 30. Mandible 70. Mentum 37 wide; ventromental plates 33, separated medially by 20, VmPR 2.6.

Comments. Material from Landis Hare from Nigeria include larval head capsules of 3rd and 4th instars. Additionally a larval exuviae under 3 coverslips on one slide is seemingly associated with the 4th instar head capsule. A second slide labelled as ‘2i’, contains an unreared larva, of appropriate size for a second instar judging from application of Dyar’s rule (% increment increase in sclerotized structure such as mandible from 3rd to 4th instar) of 1.66 between the associated 3rd and 4th instars.

No larva can be associated specifically with either S. pallidipes or S. freemani (see above). However these unallocated larvae demonstrate that larvae clearly congeneric with those of the Australian genotype ( S. subvittata ) were present at a location in West Africa where two identified species of Skusella occur.

Details of the larval habitat, a dilute water lake in the transition between guinea savannah and lowland moist forest in south-eastern Nigeria can be found in Hare & Carter (1984, 1987).

Figures

FIGURE 7. Skusella larvae. A, Head, frontoclypeus and parts farther anterior (dorsal); B–C, Antenna; D, Central labroepipharyngeal region (frontal); E, Premandible; F. Mandible; G–H, Mentum. A, B, D–G, S. subvittata; C, H, S. sp. ‘Opi’.