HOLOMETABOLOUS INSECTS 55 



males, of small size with relatively small but male-type chelae, 

 ' high ' males of large size, with relatively large male-type 

 chelae, and those of intermediate size, which have extremely 

 small, female-type chelae. 



When chela-size is plotted double-logarithmically against 

 body-size, it is found that the means for the ' low ' and ' high ' 

 males fall on two segments of a single simple curve, thus con- 

 firming Smith's view that these two types are merely breeding 

 males in their first and second seasons respectively, and that 

 those with female-type chelae are males in the non-breeding 

 phase, during which the secondary sexual characters of their 

 chelae have regressed to the female or neuter type. 



Further, on the double logarithmic plot, the curve for these 

 intermediate males first actually declines, and then mounts 

 very steeply until it meets the prolongation of the straight-line 

 curve for the low males, upon which it bends over and con- 

 tinues as the line for the ' high ' males. In other words, after 

 the regression period, the growth-ratio of the claw is much 

 higher than normal, but becomes normal as soon as the theor- 

 etical equilibrium-size is reached. 1 (Table IIIa and Fig. 32). 

 It is also seen that the frequency for chela-breadth is bimodal : 

 this will be discussed in § 5. 



§ 3. HETEROGONY IN HOLOMETABOLOUS INSECTS 



A somewhat different set of special cases is that provided 

 by holometabolous insects. Many of these possess organs 

 (usually of secondary sexual character, and these usually 

 in the male sex), which increase in relative size with increase 

 of absolute size of body. The most familiar of these are the 

 mandibles of the stag-beetles (Lucanidae) and the ' horns ', 

 cephalic or thoracic or both, of various other beetles such as 

 the Dynastidae ; but Champy (1. c.) has collected numerous 

 other examples, ranging from antennae (e.g. Acanthocinus : 

 Champy, 1924, p. 167) and forelegs, to the ' tail' on the hind 

 wing of Papilios and the swollen segments of the hindlegs in 

 certain Hemiptera, such as Anoplocnemis (Champy, 1924, 

 p. 173). See Figs. 33, 34, 91. 



Analysis shows (Huxley, 1927 and 1931) that the relation 

 between the dimensions of the organ and the body here too 



1 It is interesting to find that in I. dorsettensis, studied by Shaw 

 (1928), the regression towards female type in the non-breeding season, 

 though present, appears to be much less marked. 



