From the scholia to Aristophanes, Birds 1406, where an individual of this name is mentioned as a choregos. As such he was omitted in error from J.K. Davies, Athenian Propertied Families 600-300 BC (1971), but see idem, Wealth and the Power of Wealth in Classical Athens (1981) 161-162.
As the name is so very rare, Kirchner in PA (nos. 9159 and 9160) and LGPN ii s.v. (nos.1-2) are surely over-cautious in not equating this man with the L. who was on the board of generals in 409/8 (Diodorus Siculus 13.65.1-2); for this see Davies loc.cit. He is otherwise unknown as a poet, however. On the dithyramb poets of the new style known to the Suda see delta 1029.
The scholion which provides the present entry (see above) is hard to follow, as it confuses the various levels of discourse in which the adjectives are used. In the rampant criticism by Aristophanes and the other Athenian comic playwrights of the "new dithyramb", adjectives such as light, pallid, soft and thin seem to have been terms descriptive of its style. Leotrophides was extremely skinny, to judge from the reference to him by the comic playwright Theopompus (Kapelides, fr.1 = fr. 24 Kock, 25 Kassel-Austin). Cinesias, the dithyramb poet (kappa 1639), and Thoumantis were also pale and skinny. The word that I have translated "thin" in the passage, lepto/s, may also be used of the limp penis (cf. Aristophanes, Lysistrata 28-30 and epsilon 3006, notes) and sexual references are also possible, suggested by the term for a castrated bullock as a point of comparison.
[1] For this playwright see OCD(4) p.670, ''Hermippus(1)', and PCG 5.561ff. This fragment is from the Kerkopess fr.1 (= fr. 35 Kock, 36 Kassel-Austin), and is quoted by Athenaeus (Deipnosophists 12.551A [12.75 Kaibel], with the opening half-line "For the poor men" oi( ga\r peno/menoi).
[2] This pair reappears in Aristophanes' Gerytades fr.156 PCG 3,2.156, where they are also leptoi/. Thoumantis (theta 461, a poor man; cf. alpha 2331, lambda 868) appears on his own in Aristophanes' Knights (1268); see the scholia there and to Birds 1406.