Fig. 2. The Pairberry pattern in Tribolium mimics Drosophila. Tribolium embryos are stained with anti-Pby (in black; A,C,D,F,G,I,J-S) with Dapi counterstains (B,E,H) that correspond to (A,D,G), respectively. In addition, embryos are immunostained with second labels (in brown) of Eve (C,F,I,J,L) or En (M-S). (Q,R) Higher magnification images of A4 and T2 segments of P. Embryos are blastoderm stage (A-C) and increasingly older from D to S. (A-C) At the blastoderm stage, anti-Pby reveals protein in a broad anterior domain, while Eve is expressed in a posterior domain (C). (D-H) The mandibular Pby stripe (Mn arrow) appears anterior to the first of two nascent primary Eve stripes (F). No additional stripes appear before the amniotic fold advances (asterisk, H), concurrent with the onset of gastrulation. (I-K) A weak broad Pby stripe appears between the two primary Eve stripes (arrowhead, I,J) and splits, giving rise to the maxillary and labial stripes (Mx and La arrows, K). (L-N) A second broad stripe appears between two primary Eve stripes (arrowhead, L) and splits (M), giving rise to the first and second thoracic stripes (T1 and T2 arrows, N). Stripes of En appear just posterior to individuated stripes (M,N). (O-S) The third thoracic and first abdominal stripes have appeared, as well as a de novo broad stripe (O). The broad stripe corresponding to the eighth and ninth abdominal stripes splits (P, arrowhead), while more anterior segmental stripes overlap with stripes of En by 
one cell row (P,Q). Still more anterior stripes are restricted to the neuroectoderm (P,R). Later in development, all stripes are present and restricted to the neuroectoderm, with additional Pby staining in preantennal domains, the mandibles, maxillae and labial appendages, as well as the tips of the gnathal palps and limb primordia (S). Anterior is towards the left and all views are ventral except F, which is slightly oblique. J-S have been dissected off of the yolk and L-S have had the amnion removed. Scale bar: 250 µm for A-P,S; 19 µm for Q; and 28 µm for R.
