AUSTRALIAN CHIRONOMUS         SPECIES

One aim in these studies has been to evaluate as many characters of adults, pupae and larvae as possible in order to evaluate which ones might prove useful for separating the species that can only be recognized at present by the banding patterns of the larval polytene chromosomes or the BARCODE sequence.

Species with an Australia-wide distribution
Chironomus cloacalis Martin, 1971
Chironomus 'februarius' - currently nomen nudum, but described in Martin 1966
Chironomus 'pseudoppositus' - currently nomen nudum, but described in Martin 1966
Chironomus tepperi Skuse, 1889

Species with a tropical or Pacific distribution
Chironomus bicoloris Tokunaga, 1964
Chironomus circumdatus (Kieffer, 1916)
Chironomus nepeanensis Skuse, 1889
Chironomus 'orientalis'
Chironomus pallidinubeculosus Tokunaga, 1964
Chironomus magnivalva Kieffer, 1917
Chironomus vitellinus Freeman, 1961

Species with a north eastern distribution
Chironomus 'queenslandicus' - manuscript name
Chironomus sp. (bathophilus type)
Chironomus n.sp. Qld
Chironomus(?) blandellus Kieffer, 1906

Species with a south eastern distribution
Chironomus australis McQuart, 1847
Chironomus duplex Skuse, 1889
Chironomus 'jacksoni' - manuscript name
Chironomus maddeni Martin & Cranston
Chironomus oppositus Skuse, 1889:
form connori
form oppositus
form whitei
Chironomus 'timmsi' - manuscript name
Chironomus 'tyleri' - manuscript name (formerly C. oppositus f. tyleri)
Chironomus 'tasmaniensis' - manuscript name
Einfeldia australiensis

Species with a western distribution
Chironomus nepeanensis Skuse, 1889
Chironomus occidentalis Skuse, 1889
C. oppositus f. edwardi

Species from Norfolk Island
Chironomus 'februarius' (?)
Chironomus species NI 1 (may be as Chironomus samoensis)
Chironomus species NI 2

The description of Chironomus alternans Walker and the synonyms listed by Freeman (1961) are also included, although they are considered as uncertain.  Further description is provided for those where the types are still available:
C. alternans
C. januarius
C. subdolus

In the descriptions of adult males reference is made to the types of superior volsella shape as recognized by Strenzke (1959).  This is a helpful initial classification, but experience has shown that the types are not discrete, but are part of a continuum.  The three categories as described by Strenzke are:
S-type: The SVo is shoe shaped, i.e. it is drawn out distal-medially into a broad, rounded lobe (Fig. a-c, below) (Strenzke's figure suggests the most distal point will be at the toe of the shoe).
D-type: The SVo is ribbon-like: distally it may have a weakly thickened shoulder (Fig. d, below) (most distal point is not at the internal margin), or bent in a shallow sickle-shape (Fig. e-f, below).
E-type: The SVo has the form of an elephant's tusk; distally it is sharply graded to a point, or with an expanded knob (Fig. g-i, below) (line from base to most distal point goes outside the limits of the SV).

(Abdominal tergites may be as C. cloacalis, or may have dark band across the centre of the segment; AR 2.9-3.4; LR 1.56 - 1.65.), C. 'pseudoppositus' (Abdominal tergites as in C. cloacalis AR 2.5-3.1; LR 1.5-1.8; superior volsella less curved than in other members of the oppositus-group)
Abdomenal tergites with saddle spots: C. oppositus (LR 1.5-1.8; wing length 2.8-3.6, C. maddeni (AR 2.55-2.86; LR 1.6-1.8; wing length 2.4-3.36 mm), C. 'jacksoni' (AR 2.4-3; LR ); Chironomus 'tyleri' (AR 2.9-3.2; LR 1.53-1.66; wing length 4.3-4.5 mm).

Norfolk Island species

Adult females
No key to the females currently exists but some of the characters common to both sexes can apply, as well as additional characters from the antennae, the shape of segment X and the shape of the cercus.  Also, the dorsocentral setae begin more anteriorly than in males, the additional setae anterior to the parapsidal suture are the humeral setae and their arrangement can be useful as a taxonomic character.

In the following descriptions, reference is made to the mentum and mandible types originally devised by Webb & Scholl (1985), Vallenduuk & Moller Pillot (1997), and Proulx et al. (2013).  These classifications were made for relatively small numbers of species, but with the much larger number of species, such as in the North American fauna, they do not cover all the variability seen in these characters and so further modification has been necessary.

The MENTUM TYPE is defined only by the degree of development of the 4th lateral teeth:


Type I - height in same line as the rest of the lateral teeth;
Type II - 4th laterals reduced, height about equal to that of the 5th laterals;
Type III - 4th laterals further reduced, height less than that of the 5th laterals.

The mentum may be further classified by the characters of the CENTRAL TRIFID TOOTH:
Type IA - c2 teeth only partially separate from c1, i.e. as shoulders on c1 (figure a).
Type IB - c2 teeth slightly more separated (figure b).
Type IIA - c1 broad, c2 teeth distinctly separated (figure c).
Type IIB - c1 very broad, c2 less separated (figure d).
Type III - c1 tooth relatively narrow and much higher than the separated c2 teeth (figs e and f).
Type IV - c2 teeth well separated, not much lower than the relatively narrow c1 tooth (figs g and h).

The MANDIBLE TYPE is defined by the degree of darkening and separation of the 3rd inner tooth:
It seems better to consider the two characters separately.

Mandible length and Mdt-Mat:
Hirvenoja and Michailova (1998) illustrated that the distance between the tip of the dorsal tooth and the apical tooth could differ between related species (Mdt-Mat) (blue line in figure below).

Ventromentum
There are several measures that can be made from the ventromental plates including distance between inner margins of the plates (VPA) and the number of striae.  Two others need some explanation:

VENTROMENTAL PLATE RATIO (VMR) - ratio of the width of the marginal region of ventromentum (usually seen as a granular band under light microscopy) (a in figure below) to the distance from the anterior margin to the base of the striae (b in figure below).

VMR = a/b

PECTEN EPIPHARYNGIS -
Proulx et al. (2013) recognised 4 types of PE in North American species.  These are useful if the teeth are not worn down, as they often are in older larvae.  Type D does not occur in any known Australian species.

Type A - fine sharp rather uniform teeth.

PREMANDIBLE -
Assessment of the premandible can be difficult due to quite excessive wear and distortion in mounting. Where they are in good condition and lying flat, they can be categorised into 5 groups based on the relative widths of the teeth and whether they come to a sharp or a broad point. The teeth are measured as close as possible to their bases.
Premandible types
Type A: Both teeth narrow and coming to a fine point.
Type B: inner tooth moderately broad, about 3-5 times wider than, outer tooth. This can be split into 2 subgroups:
B1 Ð both teeth come to relatively fine points.
B2 Ð the inner tooth comes to a relatively broad point.
Type C: Both teeth are moderately broad, coming to relatively broad points.
Type D: Inner tooth very broad, outer tooth moderately broad.
Type E: Both teeth very broad and often quite short.
There is also at least one species (C. sp. Florida) recorded with a five toothed premandible similar to that of C. javanus.
Species of Kiefferulus also have a five-toothed premandible, but it is broader.

ANTENNAL RATIO (AR) - length of A1 divided by the sum of legths of A2-A5, measured on the basis of the chitinised part of each segment only, as the inter-segmental regions can extend to different extents during mounting. For this reason the AR will usually be higher than that obtained by simply measuring the total length from base of A2 to tip of A5.

Relationship on the Frontoclypeus (FC) of the distance between antennal bases and distance between S4 setae
This character gives some indication of the shape of the anterior region of the FC: the amount and extent of the narrowing at the anterior end near the antennal bases, and where the S4 setae are in relation to the broadening of the clypeus (see figure below).  This relationship can be further characterized by the distance of the S4 setae from the margins of the FC Ð most easily expressed by the fraction of the FC width between the two S4 setae.  This has two components: how far the setae are from the FC margin, and how close they are to the widest point of the FC.

Frontoclypeus with approximately equal distance between antennal bases and S4 setae.
Note also the barely visible 'ring organ' of Yamamoto et al. (2015), (more obvious at top) immediately opposite the S5 setae. This is a characteristic of species of Chironomus.

Larval types referred to in Key and in descriptions are defined here.

Einfeldia australiensis does not fit in this key as it is a more squat larva with only one pair of ventral tubules - rather like a Kiefferulus larva.  The dorsal surface has a large heart-shaped fenestra between the S4 setae.