Fig. 5. Size-dependent variation in the number of bristles in the acrostichal row on the notum of Calliphora vicina. (A-E) Thoraces of adult Calliphora together with enlargements of the boxed areas which are shown directly beneath. All thoraces are to scale. Those from large flies (70 mg; A,B) regularly display more bristles than a ‘wild-type’ thorax (55 mg; C). Conversely, thoraces from smaller flies frequently have fewer bristles (40 mg; D,E). Variability in bristle number extends to both the presutural (E) and postsutural (A,B,D) domains. Comparison with the contra-lateral hemithorax reveals that an increase or decrease in the number of bristles is sometimes associated with a displacement of the ‘wild-type’ bristles (B,E), whilst at other times the changes are superimposed on the ‘wild-type’ pattern, leaving it unchanged (A,D). (F) Variation in bristle number between individuals of different sizes of Calliphora vicina. Individual flies were weighed and their bristle patterns examined; each bristle row was treated separately. The average, or ‘wild-type’, pattern is shown in Fig. 2D and Fig. 5C. The graph indicates departures from this pattern. Variation was discovered in all four scutal rows, and also in the scutellar row: both ‘additional’ and ‘missing’ bristles occurred relatively frequently. The highest variation was seen in the bristles of the scutellar and acrostichal rows, which were also the only rows in which variation correlated with the size of the individual.
