Cricotopus cataractaenostocicola, Tachibana, 2022

Tachibana, Satoru, 2022, A new species, Cricotopus cataractaenostocicola, living in a cyanobacterial colony on vertical rocky substrates with trickling water film in Japan (Diptera: Chironomidae), Zootaxa 5178 (3), pp. 241-255 : 246-249

Cricotopus cataractaenostocicola sp. nov.

Figs. 4 , 5

Material examined. Type material. Holotype: 1 male adult (ST-CR-A1), Paratypes: 1 female adult (ST-CR-A2), 1 larva (ST-CR-L2), and 1 cyanobacterial colony with larva (ST-CR-C1); 12 May 2020, 1 male adult ( STCR-A2 ), and 1 larva (ST-CR-L1); 15 March 2021; on the natural rock wall, Kyoto (35.318285° N, 135.719367° E) , 1 pupa (ST-CR-P1); 11 March 2020; on the artificial concrete wall, Kyoto (35.312363° N, 136.692217° E), 1 cyanobacterial colony with larva (ST-CR-C2); 21 September 2020; on the artificial concrete wall, Miyazaki (31.907728° N, 131.243919° E). S. Tachibana .

Adults emerged from larvae collected. The holotype and paratypes are deposited in the Natural History Museum Vienna , Burgring 7, 1010 Vienna, Austria .

Egg. Unknown. During our field surveys, egg laying and eggs were not confirmed.

Larva: Larva consists of 13 segments, excluding the head. First segment colour darker than that of other segments. Body colour cream. Head capsule entirely black, body side brown. Eyes black. Anterior and posterior parapods present. Each parapod with more than 10 brown claws on its flat tip. Antenna composed of seven segments. Basal segment with two segments; one of the segments composed of 5 segments.

First to third instar larva: Body colour cream and lighter than that of the 4th instar larva.

Fourth instar larva: Body length approximately 5.0–6.0 mm. Head capsule approximately 0.30–0.38 mm wide. Some larvae with second segment bigger than other segments. It is unknown whether the large 2nd segment is present in all fourth instar larvae or only in larvae in the last stage of the fourth instar just before transitioning to pupa. The field was surveyed once a month for one year, and we found larvae with a bigger 2nd segment in March and May only. No data were obtained in April because the site was destroyed by construction work.

Pupa: Body length approximately 4.5–5.0 mm. Body colour deep cream. Larva metamorphosises into a pupa within a Nostoc colony. The dorsal surface almost entirely covered with fine, short spines, except for the upper one fifth in each tergites. The side of body covered with scattered approximately 50 µm long setae, no more than 20 per one tergite, spaced approximately 50 µm apart. In the ventral side, a pair of small depressions around the lower centre, between which short setae grow in dense clusters. Larva and colonies were found year-round, whereas pupae were observed only in March. Pupae did not hatch at low temperatures (<10 °C); therefore, it was assumed that many individuals hatch in spring.

Adult male: Body length from head to tip of the abdomen 4.1 mm. Body colour black. Wing membrane light brown. M-cu crossvein of wings absent. Eyes pubescent. Length of the legs is listed in Table 3 . Front tarsus I shorter than front tibia. Postnotum with median longitudinal protrusion. Scutum without median longitudinal fissure. Wing length 2.79 mm. Squama fringed with few setae. Dorsolateral setae of scutum minute, arising from small indistinct pits. Anal point approximately 20 µm long. Antenna approximately 1.0 mm long. Top segment of the antenna longer than other segments. One segment with four pits, each pit with two setae. Palpal with four segments. Genitalia with setae almost all over. The length of the setae is approximately 5 µm. A number of longer setae, approximately 100 µm, present outside of gonocoxite. Inside gonocoxite, there are few setae. The setae approximately 10 μm long.

Unit: µm. Fe: femur; Ti: tibia; Ta1-5: tarsal segments 1–5.

Adult female: Body length approximately 10.3 mm. Width of the abdomen approximately 1.7 mm. Antennas approximately 1.2 mm long. Each segment of antennas with few setae approximately 50 µm long. Abdomen with eight yellow fasciae between segments.Antenna with six flagellomeres. Genitalia with short setae. The length of the setae is approximately 5.0 µm. A number of longer setae present, approximately 100 µm.

Etymology. The name of this species is a combination of two Ancient Greek words, cataracta- meaning waterfall and - nostocicola meaning living in a Nostoc colony. As many insect larvae may live in a waterfall on a rocky wall, using only cataracta- would not have been appropriate. Thus, these two words were combined to name this species. It expressed the difference from Cricotopus living in Nostoc colony reported already. Its Japanese name is Ashitsuki-yusurika. Ashitsuki means Nostoc and yusurika means Chironomidae in Japan.

Figures

FIGURE 4. Cricotopus cataractaenostocicola sp. nov. Adult male (A–G’), A: general appearance, B: antenna, C: thorax, D: hypopygium, E: eye, F: thorax and head, G, G’, and G”: right wing. Adult female (H–L), H and H’: general appearance, I: head, J and J’: genitalia, K: antenna. Abbreviations (adult). Al: alula; An: anal vein; Ap: anal point; Ce: cercus; Clw: craw, Cp: cibarial pump; Dc: dorsocentrals; Gc: gonocoxite; Gs: gonostylus; Hl: halter; Ivo: inferior volsella; La: labrum; Pm: palpal segments; Po: Postnotum; Sct: scutelium; Scu: scutum; Sq: squama.

FIGURE 5. Cricotopus cataractaenostocicola sp. nov., larva and pupa. Larva (A–G), A and A’: general appearance, B: dorsal view of head capsule, C: frontal view of head, D: larval left antenna, E: top of the head, F: anterior parapods, G: posterior parapods. Pupa, H, H' and H”: general appearance. H’ is a combination of three pictures, two dotted lines are borders. I: tergite IV from the side, J: tergite VII from the side, K: face. Photos C–F, H’ and K were obtained by an electronic microscope. Abbreviations (larva). Ap: anterior parapods; As: anal seta; Pp: posterior parapods; Ta: anal tubules. Abbreviations (pupa). Al: anal lobe.