Yamamoto (2002) has suggested that this species should be in a separate subgenus Austrochironomus, as type of the subgenus. However there is doubt that there is a consistent set of characters for the species he included.
C. javanus and C. vitellinus are closely related and there is clear evidence that some hybridization can occur in the limited area where both species occur together, e.g. in Malaysia.
Adult:
Many specimens attributed to C. javanus are actually C. vitellinus and C. javanus appears to have a relatively restricted distribution in India, Java, and Malaysia.
Other than the original description, the only reliable further descriptions for this species are those of Johannsen (1932) and Chaudhuri et al. (1992)(whose specimens appear to be larger, possibly due to being reared in laboratory), plus a specimen from Penang:
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Hypopygium with long tubular anal point, strongly turned down. Superior volsella well developed and curved, perhaps closest to E(h) of Strenzke (1959); Inferior volsella reaching just beyond the end of the Superior volsella, about 1/3 of gonostylus length, with 12-14 incurved setae. Gonostylus quite swollen and conspicuously narrowed over posterior half with 5+1 or 1+4+1 setae at tip.
Female
The female has hardly been described as Kieffer gave few metrics, so the only information appears to be from Chaudhuri et al. (1992):
Body length 3.69 (3.57-3.89) mm. Wing length not given.
Antennal segments (micron): 10 : 7 : 8 : 9 : 13; AR 0.38; A5/A1 1.3. Necks of segs. 2-4 about 50%.
No information on palps, clypeus, thoracic setae or legs. Kieffer gives abdomen as green, unmarked. Cercus almost pointed at posterior end, large bulge on ventral margin.
Pupa and Fourth instar larva: See C. javanus immatures.
Cytology: The chromosomes of C. javanus have not been studied, but there is a photograph which is probably this species (below): Four polytene chromosomes with the thummi-cytocomplex combination AB, CD, EF, G. Centromeres are obvious but not heterochromatic. Essentially terminal nucleolus in arm G, possibly with a BR close to it. A large puff is developed about one third from the distal end of arm B. No reported polymorphism.Molecular: The mitochondrial CO1 barcode sequence is available in GenBank and the BOLD database for a few specimens. Although the sequences in BOLD are in a single Bin, there is a suggestion that the distribution is bimodal, with the few C. javanus sequences separated to the right of the main group. The BARCODE sequences differ by about 47 base positions (this does not include some rare polymorphisms where one or two C. vitellinus specimens carry the sequence present in C. javanus), and the majority are in the 5' region (as is common for differences between closely related Chironomus species):
There is one specimen from Penang (MYA.1.3 BMAES 11F) in which the COI sequence is that of C. javanus, but the larva is typical of C. vitellinus – suggesting that the female parent was C. javanus and the male parent C. vitellinus. This is in the small region in which both species are known to co-exist.
The present measurements differ in some significant details from those of Kieffer's description, although the other details of colour and the unusual genitalia correspond.
The males are easily recognised by the unusual genitalia, particularly the tubular anal point, and the larvae by the 6-toothed premandible. The pupa is a fairly typical for Chironomus.Males can be separated from the relatively similar C. vitellinus by the tubular anal point rather than expanded at the distal end (see below ) and the placement of the setae on TIX, although that species has been regularly misidentified as C. javanus as can be readily seen from the figures of the male hypopygium. The larvae can be separated by the number of teeth on the premandible (6 vs. 7 – so the excellent photograph of the premandible in Cranston (2007) is C. vitellinus, not C. javanus), the unusually short 3rd segment of the antenna (shared with C. vitellinus) and the teeth of the mandible (type II-IIIA vs type IIIC).
Found:Type locality - Buitenzorg, Java, INDONESIA, also Sumatra (Johannsen 1932).
India - Bankura, Chinsura, Dhaniakhali, all West Bengal (Chaudhuri et al. 1992); Madurai (9.925°N, 78.120°E), Tamil Nadu; University
of Jammu Campus (32.73°N 74.87°E) Jammu & Kashmir; Kasar Lake (18.82°N, 76.20°E), Kulcatta.
Indonesia - Sumatra.
Malaysia - Minden, Penang; Tregganu; Bukit Merah Agricultural Experimental Station (BMAES) Permatang Pauh, Penang
(5.13°N, 100.13°E); Parit, Perak.
Apparently limited distribution through India, Java and Malaysia, in rice paddies and small temporary water bodies, even sewage works.
The redescription of adults and immatures from Malaysia by Al-Shami et al. (2012) clearly refers to C. vitellinus but they did also collect at least one specimen of C. javanus (figure above).
Dr. Midya has an alternative species from India identified as C. javanus and L. Karunakaran described another species as C. javanus in an unpublished thesis (Martin 2022).