Phase polymorphism in Locusta migratoria: the relative effects of geographical strains and albinism on morphometrics

An albino strain, which had originated from Okinawa, Japan, and a normally coloured strain, which had originated from West Africa, have been used to s tudy density-dependent morphometric phase characteristics and their changes in adults of the migratory locust, Locusta migratoria (L.). By repeated cr ossings we also obtained congenic albinos and normal phenotypes and investi gated their morphometrics with increasing West African genome, eventually r eaching 99.6% West African and 0.4% Okinawa gene pool. The data were analys ed by the classical morphometric ratios (F/C and E/F; F=length of the hind femur, C=maximum width of the head, E=length of the fore wings), as well as by canonical discriminant (multivariate) analysis. The latter was based on measurements of F, C and E (as above), as well as of M (minimum width of t he pronotum) and H (maximum height of the pronontum). Okinawa albinos showe d more solitarious morphometrics and a smaller amplitude of morphometric ph ase change than West African normal phenotypes. Both the morphometric ratio s and the canonical discriminant analysis demonstrated clearly that these d ifferences were caused primarily by the strain (Okinawa vs. West African). However, the pigmentation (albino vs. normal colouration) also affected mor phometric phase differences; albinos showed more solitarious morphometrics and somewhat more restricted morphometric phase change than congenic normal phenotypes. The effect of the pigmentation was considerably smaller than t hat of the strain. The results refute Nolte's claim that albino locusts con stitute an extreme solitarious phase, even under crowding. However, Nolte's less extreme claim, that albino locusts have more solitarious morphometric s than normally coloured locusts, is validated by the present results.