Hydrotaea affinis Karl, 1935

Vikhrev, Nikita E., 2023, Review of the Hydrotaea meteorica group (Diptera, Muscidae), Amurian Zoological Journal XV (4), pp. 838-846 : 839-840

Hydrotaea affinis Karl, 1935

Fig. 5

Hydrotaea affinis Karl, 1935: 38 . Type locality: Tainan, Formosa (= Taiwan).

Hydrotaea zao Shinonaga & Kano, 1971 . Type locality: Japan, Honshu , syn.nov.

Hydrotaea affinoides Feng & Feng, 1997 . Type locality: China, Sichuan prov., Yaan env., Mt. Zhougong (29.946 ° N, 103.040 ° E), 1700 m, syn.nov.

Hydrotaea affinis Karl, 1935 : Emden (1965, redescription).

Hydrotaea zao Shinonaga & Kano, 1971 : Shinonaga & Kano (1971); Shinonaga (2003, redescription).

Hydrotaea affinoides Feng & Feng, 1997 : Fan (2008: 484, redescription in Chinese; 1017– 1023, identification key, in English.

Material examined: INDIA, West Bengal state, Kalimpong , 27.06 ° N, 88.43 ° E, 16– 30.11.2013, K. Tomkovich, 1♂ ; RUSSIA, Primorsky Reg.: Andreevka env, 42.7 ° N, 131.1 ° E, 26– 31.07.2018, N. Vikhrev, 3♂, 21♀ , first record for Russia. THAILAND: Chanthaburi province, Khao Khitchakut National Park , 12.82 ° N, 102.13 ° E; 1– 4.11.2009, N. Vikhrev, 1♂ ; 3– 6.12.2011, D. Gavryushin, 1♂; N. Vikhrev , 1♂ ; Nakhon Ratchasima province, Khao Yai National Park , 11.02.2009, N. Vikhrev, 1♂ .

Distribution. SE Asia. China: Taiwan and Sichuan provinces; India: Madras and West Bengal states; Japan, Honshu; Russia, Primorsky region; Central Thailand.

Discussion on synonymy. Males of H. affinis are unmistakable due to a row of 4–6 long apically downcurved pv setae in the apical quarter of t3 ( Fig. 5 ). More precisely, they were easily distinguishable before two more species with the same modification of hind tibia were described from Japan and China. Shinonaga & Kano (1971) and Shinonaga (2003) compared H. zao with H. meteorica but did not compare it with H. affinis . H. affinoides was described as a species with calypters ‘dirty white’ while H. affinis has calypters ‘pale brown’ ( Fan 2008).

1. Let us compare the diagnostic value of the two mentioned characters: the modified t3 and the colour of calypters. The most appropriate analogy belongs to William Paley and is widely known from Richard Dawkins’s book The blind watchmaker: a stone has a common natural origin, whereas a watch implies the presence of an intelligent design. The row of curved pv setae on t3 is a ‘watch’: it is a complex and ordered structure that was created by the directed action of natural selection. It is obvious that such a modification occurred only once; therefore, all its owners are at least closely related organisms. Another ‘watch’ character is the unusual shape of apical teeth on the male fore femur: swollen spines dilated basally and sharpened apically ( Fig. 4 ). This synapomorphic character is shared by the species of the H. meteorica group, and actually this was the reason of recognizing this group. In such terms the characters like dirty white/pale brown colour of the calypters or the number (4 to 6) the apically curved pv setae on t3 are ‘stones’. Below, I will use the terms ‘strong’ or ‘weak’ characters instead of ‘watch’ and ‘stone’.

The description of new species on the base of weak characters is not convincing unless there are at least two correlating independent weak characters and intraspecific variability has been studied on a large enough series of specimens. Neither H. zao nor H. affinoides satisfies these conditions.

2. By analogy with ‘case law’ (in Russian: прецедентное право), I’d like to propose on this example the principle of ‘case taxonomic approach’ (i.e. in Russian: прецедентный таксономический подход). H. affinis is an uncommon species poorly represented in insect collections. Instead of describing new H. affinis -like species from few available specimens on the base of difference of the calypters colour, the authors should have started with studying variability of the same character in related, much more common and much better represented in collections H. meteorica . In H. meteorica the colour of calypters varies widely from yellow to dark brown, commonly there are yellow and brown-calypter specimens from the same locality. I consider this variability as intraspecific, either inherited or induced by external conditions, such as temperature. Only if someone convincingly justifies the need for splitting H. meteorica into several species on the base of variability of the calypters colour, it would be reasonable to discuss the same approach to H. affinis .

3. The third principle — ‘no difference, no validity’ — is a practical application of the main approach to any scientific investigation, namely Occam’s presumption ‘not to produce unnecessary entities’. If author(s) forgot (or ‘forgot’) to compare a newly described species with a really similar one(s) but compared it only with an obviously different one(s), then such new species goes to synonymy without long discussions. This principle may well be applied to H. zao .

So, Hydrotaea affinis Karl, 1935 = H. zao Shinonaga & Kano, 1971 , syn.nov. (using the above suggested principles 1 and 3) = H. affinoides Feng & Feng, 1997 , syn. nov. (using the above suggested principles 1 and 2).

Figures

Figs. 2–5. 2 — H. spinigena, male head, lateral; 3 — H. spinigena, male mid leg (modified from Xue & Chao 1998: 905, figs 2097Fe and 2097Fp); 4 — H. nigribasis, male fore leg (as H. australis, from Emden 1965: 313, fig. 83b); 5 — H. affinis, male hind tibia (as H. affinoides, from Fan 2008: 484, fig. 153c) Рис. 2–5. 2 — H. spinigena, гоΛова самца сбоку; 3 — H. spinigena, среΑняя нога самца (с изменениями по Xue & Chao 1998: 905, figs 2097Fe и 2097Fp); 4 — H. nigribasis, переΑняя нога самца (как H. australis, по Emden 1965: 313, fig. 83b); 5 — H. affinis, заΑняя гоΛень самца (как H. affinoides, по Fan 2008: 484, fig. 153c)