Chaetocnema (Chaetocnema) confinis Crotch, 1873

Ruan, Yongying, Yang, Xingke, Konstantinov, Alexander S., Prathapan, Kaniyarikkal D. & Zhang, Mengna, 2019, Revision of the Oriental Chaetocnema species (Coleoptera, Chrysomelidae, Galerucinae, Alticini), Zootaxa 4699 (1), pp. 1-206 : 34-38

5. Chaetocnema (Chaetocnema) confinis Crotch, 1873

( Figs. 21 , 22 , 23 ) (introduced species in Asia, originally from North America)

Chaetocnema confinis Crotch, 1873: 75 . TL: USA (Southern States), TD: MCZC.

Chaetocnema flavicornis LeConte, 1878: 418 .

Chaetocnema etiennei Jolivet, 1979: 641 . Synonymized by Döberl, 2010: 509.

Distribution: China (Fujian, Jiangsu, Guangxi, Guangdong, Taiwan); Japan (Ryukyu island), Thailand, Vietnam, India, Philippines; Australian region; Nearctic region; Neotropical region; Afrotropical region.

Host plants: Members of Convolvuaceae are the host plants of C. confinis , commonly known as the sweet potato flea beetle. This is an economically important, invasive pest of sweet potato Ipomoea batatas ( White, 1983; 1996) and I. aquatica , a popular vegetable in Asia. In its native North America, C. confinis has also been reported on a variety plants across families ( Blatchley, 1924; Hallock, 1939). Kalaichelvan et al. (2001) reported its occurrence in India.

We find that Chaetocnema confinis Crotch feed on Ipomoea cairica (L.) Sweet in Shenzhen, Guangdong, China. The phenomenon can be frequently seen in the field, city parks and gardens in Shenzhen. Currently, Ipomoea cairica is considered as an introduced plant species or noxious weed to China and many other contries across the world, it cause harm to other plants in southern China.

Host plant records: Blatchley (1924: 39): soy–beans, basswood, wild cherry, buckeye, velvet beans, oak, and maple.

Hallock (1939: 122): tobacco, potato, tomato, morning glory, Indian mallow, sweet potato, wheat, rape, artichoke, pigweed, and burdock.

White (1996): sweet potato; cultivated morning glory; on corn; on Convolvulus arvensis ; Convolvulus sepium ; on cotton; on fruit of grapes; on Pharbitis cathartica ; accidental on Hibiscus ; peach foliage; pokeroot in tob. field; on nightshade leaves; orchard grass; on Norway maple; on tobacco; swept from alfalfa; on strawberry; on turnip leaves; on bean foliage; Prunus americana ; apple; from B. blue stem; from L. blue stem; on tomato; on Catalpa ; Ipomoea sp.; Ipomoea batatas ; on lima bean; on flowers of Prunus virginiana ; on foliage of white ash; flowers and foliage of Viburnum prunifolium ; night sweeps in resaca; Convulvulus.

Kalaichelvan and Verma (2005): Ipomoea aquatica , I. batatas , I. carnea ssp. fistulosa , I. cairica and I. violacea .

Prathapan and Balan (2010): I. batatas , I. cairica , I. nil , I. obscura , I. pes-caprae , I. pes-tigridis , I. pileata , Merremia tridentata and M. vitifolia .

Description: Body length: 1.50-1.70 mm (size of Oriental specimens. North American specimens are slightly larger). Body width: 0.80–1.00 mm (measured on Oriental specimens). Ratio of length of antenna to length of body: 0.64–0.65. Ratio of elytron length (along suture) to width (maximum): 2.00–2.20. Ratio of pronotum width (at base) to length: 1.70–1.75. Ratio of length of elytron to length of pronotum (along middle): 2.70–2.80. Ratio of width of elytra at base (in middle of humeral calli) to width of pronotum at base: 1.02–1.10.

Dorsum bronzy. Dorsum, head finely reticulated. Antenna completely yellow brown. Tibiae, profemora and mesofemora light brown. Metafemora dark brown. Tarsi yellow.

Head hypognathous. Frontal ridge narrow and convex. Frontolateral sulcus present. Suprafrontal sulcus poorly developed. Orbital sulcus deep. Ratio of width of frontal ridge (excluding margin) to width of antennal socket (excluding margin): 1.40–1.45. Number of punctures on vertex: 5–6 on each side near eye. Number of punctures on orbit: 0–2 on each side. Number of punctures on frons (triangular area surrounded by frontolateral sulcus and clypeus): 0. Number of setae on clypeus: approximately 20. Number of setae on labrum: 6. Anterior margin of labrum slightly convex at middle.

Pronotum without longitudinal impressions near basal margin. Deep row of large punctures at base of pronotum absent. Pronotal base evenly convex. Lateral margins of pronotum slightly convex, converging forward. Anterolateral prothoracic callosity truncate, oblique and long. Posterolateral prothoracic callosity poorly developed. Diameter of pronotal punctures 2 to 4 times smaller than distance between them.

Excavation on metatibia moderately deep. Large lateral denticle on metatibia sharp. Metatibial serration obtuse.

Elytra with slightly convex lateral sides. Elytral punctures larger than those on pronotum. Punctures on elytra arranged in regular rows, including peri-scutellar row. Interspaces between striae of punctures smooth and glabrous. Number of rows of minute punctures on each interspace: 1–2. Elytral humeral callus well developed.

First male protarsomere slightly larger than second, not distinctly larger than that of female. Excavation on metatibia moderately deep. Large lateral denticle on metatibia obtuse. Metatibial serration proximal to large lateral denticle absent or poorly developed.

Apex of aedeagus in ventral view narrowing gradually with obscure polygonal markings laterally. Ventral lon- gitudinal groove absent. Apical denticle absent in ventral view. Minute transverse wrinkles absent on ventral side. Aedeagus in lateral view unevenly curved, somewhat sinusoidal near apex. Maximum curvature in lateral view situated at middle.

Spermatheca with receptacle globose. Spermathecal duct curved. Spermathecal pump much shorter than receptacle, with rounded apex. Apex of vaginal palpus subtriangular. Anterior end of anterior sclerotization broadly rounded. Vaginal palpus parallel-sided. Posterior sclerotization longer than wide. Posterior sclerotization wider than anterior.

Last visible abdominal tergite of female with a longitudinal groove in middle. Two rows of punctures present in longitudinal groove. Last visible abdominal tergite of female fully covered with distant punctures, punctures closer to each other in apical half.

Types: Photos of Holotype examined: 1♂ (Holotype) (MCZC), 1) orange disc = Southern States; 2) Gulf States; 3) Va., N.C., S.C., eastern Tenn.?, Ga., Ala., Miss., Fla., Ark.?, La.; 4) J. L. LeConte Coll.; 5) Type 5007; 6) confinis Crotch ; 7) Lectotype Chaetocnema confinis Cr. by R. White '96".

Material: 1♀ ( IZCAS), China, Guangxi, Longzhou, Nonggang, 330m, 2000.VI.16, Jian Yao, IZCAS, Chaetocnema confinis Crotch., 1873 , Det. Yongying Ruan, 2016; 5♀ ( IZCAS), China, Fujian, Yongtai, 1997, leg. Bangkan Huang, Host plant: Ipomoea aquatica , Ipomoea batatas ; 4♀ ( IZCAS), China, Fujian, Yongtai, 1990, Host plant: Ipomoea aquatica ; 16♀ ( BMNH), Taiwan ( China), Sanhsia, Nantou Hsia, 13. X. 1995, Ex Ipomoca aquatica, L. Y. Chou leg., Pres. by Int. Inst. Ent., BMNH (E) 1997–202; 9♀ ( TARI), Taiwan ( China), Chiayi (#28668), Agri. Res. Inst., 06.II.2017, Leg. Y.-P. Liang; 13♀ ( IZCAS), China, Guangdong province, Shenzhen, Nei-lingding Is., Leg. Ruan, 2018-V-4, N22.4043° \ E113.8024°, 23m, host plant: Ipomoea cairica (Convolvulaceae) . 1♀ ( BMNH), Thailand, Nan Province, Lainan, 21–22.IX.2012, cabbage farm, 18.579N, 100.757E, LN3 Malaise trap, leg. D. L. J. Quicke, BMNH(E) 2015–75; 1♀ ( BMNH), Sabah, Malaysia, A. R. C. Tuaran, V. F. Wong, French bean, 16.VII.1982, 94, C.I.E. Coll., A.14281, Chaetocnema sp. det. M. L. Cox, 1982, Pres. by Comm Inst Ent, B.M. 1982–1; 6♀ ( USNM), Malaysia, Sabah, Tanjung Aru Beach, 8.VIII.1983, leg. G. F. Hevel & W. E. Steiner. Loan from USNMNH 2065634; 10♀ ( BMNH), Sabah, Malaysia, A. R. C. Tuaran, Peter Goh, P. G.160, on sweet potatoes leaf, 26.X.1994, I.S.A.F. 1319, 874, Pres. by Int. Inst. Ent., BMNH{E} 1997–III; 19♀ ( USNM), Malaysia, Sabah, VIII–IX.1983, leg. G. F. Hevel & W. E. Steiner, loan from USNMNH 2065634; 2♀ ( USNM), South India, Easten Ghats Karnataka, 14 km, E. Tumkur, leg. Konstantinov, Prathapan, Saluk; 2♀ ( USNM), Sri Lanka, Gannoruwa, 13.II.2002 on Kankung, leg. S. Basnagala, loan from USNMNH 2065634.

Material from Palearctic Region: 4♀ ( BMNH), Kunigami Okinoerabu Ryukyu ( Japan), 5. XI. 1996, A. Tanaka; Pres. by Int. Inst. Ent., BMNH(E) 1997–202 .

Material from Austrilian Region: 3♀ ( USNM), New Caledonia, 20m, Koumac, 6–12.I.1991, leg. Wiesner & Worm, Chaetocnema indica det. Döberl.

Material that has been compared with type by R. White: 1♀ ( USNM), USA, San Antonio, Chaetocnema confinis Crotch det. White, Compared with type; 1♂ ( USNM), USA, on Spinach , Hill, N. M. 13.X.1943, Chaetocnema confinis Crotch det. White, 1992; 1♀ ( USNM), USA, Iowa, Polk Co., Walnut Woods Pk., 16.V.1983, J. E. Wappes .

Remarks: Chaetocnema confinis is native to Nearctic Region (see White, 1996), and was introduced to China and Oriental Region. Specimens from the Oriental Region are distinctly smaller (body length: 1.50–1.70 mm) than those from North America (body length: about 2.00 mm); Males do not occur outside North America, where it is introduced, and only females occur in the Oriental Region, indicating parthenogenesis (we have examined 80 specimens from the Oriental Region and all of them are females, which is very unusual for Oriental Chaetocnema ).

This species closely resembles C. indica and C. jinxiuensis sp. nov. However, punctures on pronotum are much closer and coarser in C. confinis compared to the other two species. Three females from New Caledonia were examined and they are slightly larger in size compared to the Oriental specimens.

Chaetocnema minutissima from south America appears to be identical with C. confinis , based on external characters. More studies may prove them to be conspecific.

Figures

FIGURE 21. Chaetocnema confinis (specimens from Nearctic Region). A Male habitus. B Pronotum. C Head, frontal view. D Aedeagus, ventral view. E Aedeagus, lateral view. F Apex of aedeagus, dorsal view. G Vaginal palpi. H Spermatheca. I Pygidium (tergite 7) of female.

FIGURE 22. Chaetocnema confinis (specimens from Oriental Region). A Female habitus. B Pronotum. C Head, frontal view. D Vaginal palpi. E Spermatheca. F Pygidium (tergite 7) of female. G Feeding troughs on leaf of Ipomoea batatas.

FIGURE 23. Chaetocnema confinis on host plant (specimens from Oriental Region). A individual on host plant, lateral view. B Host plant: Ipomoea cairica (Convolvulaceae) [the host plant is a well-known invasive plant in China]. C patterns of injuries on leaves of host plant caused by adults. D a photo of collecting location [Guangdong province, Shenzhen, Nei-lingding island, 2018-V-4, N22.4043° \ E113.8024°, 23m].