C. occidentalis Skuse, 1889

Fourth instar larva:  Large bathophilus-type larva.  Head capsule heavily darkened over most of the gula, widest at the posterior margin and highest at the centre the gula; Fronytoclypeus very dark and other regions of dorsal head darkened.  Dorsal and ventral anal tubules rather different in shape, ventral pair longer and more rounded at tip (505-885 µm), the dorsal pair shorter and more pointed (430-505 µm).  Oesophageal aperture about 99.3 (78-127) µm wide and 3.9 (3.4-5.0) times wider than deep.
Mentum Fig. c with generally sharp teeth; 4th laterals reduced to about level of 5th laterals (type II); c2 teeth reasonably well separated (type IIA), pointed, c1 tooth relatively broad with straight sides.
Ventromental plates Fig. d about 257.1 (212.5-277) µm wide and 3.7 (2.9-4.2) times wider than deep, 1.03 (0.88-1.1) time the mentum width; with about 45.8 (39-44) moderately spaced striae.
Pecten epipharyngis Fig. a with 15.1 (13-17) mostly broad teeth that were quite worn in the available specimens.  Premandible with inner tooth usually coming to a relatively broad point and about 3-5 times wider than the outer tooth that comes to a fine point (ty. 2b).
Basal segment of antenna Fig. b relatively long and about 3-4 times longer than wide; RO from a quarter to almost half up from base of segment; AR about 2.34 (1.67-2.90); A2/A1 about 0.23; A2 less than width of A1; A5 almost as long as A3; antennal proportions (µm) 157 : 36 : 9 : 14 : 8.
Distance between the antennal bases (200.9 (157-230) µm) essentially about the same as that between the S4 setae (196.3 (170-207) µm) so that either can be greater on any particular larva.  S5 setae abt. level with nearby RO or slightly posterior.
Mandible Fig. e with 3rd inner tooth pigmented and relatively well separated (type IIIB-C); about 18.1 (15-23) furrows on outer surface near base; 13.3 (10-16) taeniae in the Pecten mandibularis; Mdt-Mat 37.2 (25-40); MTR 0.36 (0.23-0.43).

Cytology:  3 polytene chromosomes with the modified pseudothummi arm combination AEG, BF, CD.
Arm G with a subterminal nucleolus followed by a large Balbiani ring, separated by about 12 bands; a further BR is involved in a polymorphic inversion.
Polymorphism in arms B, D and G-E.
occA1:    1a-e, 4c-a, 12a-c, 3i-f, 9 - 8a, 2d - 3b, 6c - 4d, 11 - 10a, 2c - 1f, 3e-c, 6d - 7, 13a - 19
occD1:    1 - 2c, 17c-a, 10c - 7c, 2f-h, 16 - 10d, 3 - 7b, 2ed, 17d - 24
occE1:    approx  7 - 3f, 10c - 12, 10b - 8, 3e - 1, 13                  3 inv. steps from australis A1
occF1:    1 - 2a, 10 - 2b, 11 - 23                                                      as oppositus F1

Nucleoli and location of C-bands studied by Lentzios & Stocker (1979) and Lentzios et al. (1980).

Pupa:  Dark, relatively large exuvia, shagreen pattern of dark spines on posterior 2/3 of segment II, extending to the whole length by segment V and bilobed in VII & VIII.  In female exuvia there is a clear region in the midline of each segment, less obvious in males.  Pedes spurii B well developed on segment II, but much less so on segment II; pedes spurii A well developed on segment IV, about 154-300 µm in length (the smallest figure is from a female), with spine patches on segments V-VII.
Respiratory base more or less oval, about 116-187 µm long, 38-68 µm wide, but base of filaments almost bilobed.
L-setae at anterior margin of intersegment of III/IV and IV/V quite long (up to about 140 µm), but those of IV/V probably the longer.

Some characters given in Table below:











Length (mm)



10.3 - 11.3

Inner margin wing case (mm)



Cephalic tubercles (µm)




 40 - 89

Cephalic bristles (µm)

 abt 90


 abt 75


Recurved hooks on abd. seg. 2


66 - 71

Spines on postero-lateral spur



5 - 7

Swim fin taeniae (one side)


96 - 100

Cephalic tubercles about40-90 µm and 0.75-1.2 times higher than width at base, in female about 137 µm and 1.4 times higher than wide.
About 66-72 recurved hooks on segment II, covering about 52-66% of segment width (again lowest value is for a female).  About 5-7 closely applied spines on the posterolateral spur of segment VIII.
About 96-110 taeniae on each side of the swim fin.

C. occidentalis can be readily separated from C. duplex at the pupal stage on the basis of the pupal spurs, in which the spines are closely applied in C. occidentalis but spread in C. duplex. The pupal spur of C. occidentalis resembles that of C. australis but with fewer spines.

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Modified: 20 March 2024
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