Species 3a.  C. decorus larva and cytology

Fourth instar larva a small to medium sized (female 10.7-13.8 mm; male 9.4-13.1) (12 mm according to Johannsen, 1905) bathophilus- or melanotus-type (93-160 µm).  Anterior pair of ventral tubules slightly longer (ant. 1.30 (0.90-1.72 mm; post. 1.21 (0.80-1.57) mm.  In his original description (see above) Johannsen (1905) does not mention lateral tubules but in Johannsen (1937) the larva is noted to possess lateral tubules.  However this is a polymorphic character, apparently present in more northern populations, but lacking in the more southern populations of Mississippi and New Mexico.
Anal tubules 2-3 times longer than wide, variable in length - shortest in Mississippi, and longest in Ontario and Wisconsin, often with a constriction in the middle.
Gular region very dark over posterior half to two thirds, extending beyond the edges of the mentum, higher at lateral margin and wider about a third from posterior margin; frontoclypeus pale.
Mentum (Fig. d) with relatively sharp teeth; c1 tooth relatively broad with parallel sides;  c2 teeth reasonably well but not completely separated (type IIA-III); 4th laterals reduced down to about height of 5th laterals (type (i)-II).
Oesophageal opening about 56-115 µm wide and 2.5-4.4 times wider than deep.
Ventromental plates (Fig. e) about 3.5 times wider than deep, and separated from each other by 0.37-0.42 of the width of the mentum, with about 34.8 (30-51) striae.  Pecten epipharyngis (Fig. a) with about 13.75 (10-15) teeth of type A or sometimes type B.
Premandible (Fig. b) with the broad inner tooth about 2-4 times wider than the outer tooth which narrows markedly along its length, probably about equal length when not worn.
Antenna (Fig. c) relatively short, about 33-46% of ventral head length;  AR about 2.43 (2.19-2.75);  basal segment about 3.2 (2.6-3.7) times longer than wide, ring organ about a third to a half way up the segment from the base; segment lengths (µm) 121 : 27 : 7 : 11 : 6 .
Distance between antennal bases generally greater than that between the S4 setae, which are separated by about 0.7-0.9 of the width of the frontoclypeus at that point.
Mandible (Fig. f) with the third inner tooth slightly darkened and sometimes slightly separated (type I-IIB), about 16.6 (12-20) furrows on outer surface near base; 10.7 (8-13) taeniae in Pecten mandibularis; Mdt-Mat 32.3 (25-38), MTR 0.38 (0.29-0.48).
Larvae from southern regions are bathophilus-type, while those from Wisconsin and Ontario seem to be semireductus- or even plumosus-type.

Cytology:  4 polytene chomosomes (arms A-D or arms E-G) with the thummi arm combination AB, CD, EF, G.  Very polymorphic with inversions in all arms.
Arm G with an a nucleolus near one end - Rothfels and Fairlie (1957) indicate it is in a region about 10 bands from the end.  However the whole region at the end may appear heterochromatic (see figure below) with no nucleolus obvious.  There are three BRs whose relative position depends on the inversion sequence present.  Arm G is often only paired at end away from nucleolus.  No nucleolus in the long chromsomes.
Chromosome AB is somewhat difficult to recognise from the Keyl pattern, since the "olive" in arm A is not obvious and the 4 characteristic bands of arm B are not near the centromere but in variable positions due to inversion polymorphism.  A large puff is sometimes developed in group 7, about one third from the end of arm B.
Polymorphism occurs for all arms.  Rothfels and Fairlie, in their study of 354 individuals, recorded about 30 inversions, including most of those in our smaller studies, with the exception that they found only one sequence for arm F in their Ontario populations, while at least 6 inversions were present in our New Mexico samples.  The inversions from our samples are listed below, with comparison to the R & F sequences where possible.

decA1:    Pattern difficult to identify as the bands of the typical "olive" are dispersed.
decA2:    Large medial inversion.
decA3:    A distal inversion of A2.    May correspond to inversion A of R & F.
decA4:    A small medial inversion.
decB1:    Characteristic bands 20-23 not near centromere but about the middle of the arm, puff (gp. 7) towards distal end of arm.
decB2:    Inversion of about half of the arm, with proximal breakpoint only 10-12 bands from the centromere.
decB3:    Small inversion just proximal to the puff.
decB4:    Small inversion adjacent to the centromere.
decB5:    Small inversion of the more distal region of B2 and apparently sharing the distal breakpoint.
decC1:    Typical groups 3-4 towards the distal end.
decC2:    A very large inversion of about 60% of the arm, with one break distal of the typical bands; as inversion B of R & F.
decD1:    Band groups 16-18 probably towards the distal end of the arm.
decD2:    Large inversion of about 2/3 of arm, proximal breakpoint probably in group 23.
decD3:    Large inversion derived from decD2
decE1:    1 - 3e, 8 - 5, 9 - 10b, 4 - 3f, 10c - 13                      i.e. as maturus, stigmaterus and Inv. A of R & F.
decE2:    1 - 3e, 8i-e, 3f - 4, 10b - 9, 5 - 8d, 10c - 13            i.e. as Inv. S of R & F.
decE3:    appox. 1a-d, 4-3f, 8e-i, 3e-a, 1i-e, 10b-9, 5-8d, 10c-13
decF1:    1, 9 - 2, 10 - 23                                                i.e. as blaylocki, utahensis, etc.
decF2:    1, 3d - 9, 3c - 2, 10 - 23
decF3:    1a-d, 9 - 3d, 1i-e, 3c - 2, 10 - 23(?)                      from F2
decF4:    1, 3d - 9, 3c - 2d, 18 -10, 2a-c, 19 - 23          from F2
decF5:    1, 3d - 9, 17 - 10, 2 - 3c, 18 - 23                         from F2
decF6:    1a-d, 9 - 3d, 1i-e, 3c-2, 10 - 18, 23 - 19              from F3?
decF3+4:    1a-d, 9 - 3d, 1i-e, 3c - 2d, 18 - 10, 2a-c, 19 - 23
decG1:    Subterminal nucleolus and three BR from about 1/3 from nucleolar end to 1/3 from other end, usually only paired at distal end.
decG2:    A small inversion of mid region to just distal of middle BR.
decG3:    A larger complex inversion of almost half the arm, towards the distal end, illustrated in Fig. 1(11) of Rothfels and Fairlie (1957).