Deweyanae are lax plants having setaceous bracts, spikes that are usually gynecandrous, distigmatic pistillate flowers, and perigynia that are spongy-based, non-papillate, unwinged
at the margins, and relatively long-beaked.
This is reflected in their morphology and the distance they are likely to travel, with the unwinged individuals relatively more sedentary than the winged individuals, which in this study are the migrants.
Here the theory of aerodynamics and a model of the optimum partitioning of energy in aphids are used to account for the relative size of winged and unwinged aphids, and the size of the gonads and wing beat frequency of migrant aphids of different sizes.
For quantification of the relative size of winged or unwinged aphids the Kindlmann and Dixon (1992) model, which generates life table data for unwinged aphids, can be used to generate similar data for winged aphids with the following modifications:
Results from Kindlmann and Dixon (1992) indicated that under particular conditions of temperature and food quality the relationship between fitness, [Phi], expressed as the instantaneous population growth rate, [r.sub.m], and body size, [m.sub.A], in unwinged aphids is a unimodal curve, f([m.sub.A]), for which df([m.sub.A])/dt [greater than] 0 if [m.sub.A] [less than] [m.sub.apt] and f[prime]([m.sub.A]) [less than] 0 if [m.sub.A] [greater than] [m.sub.apt].
The gonads make up about one-half of the total body mass in unwinged aphids (Kindlmann and Dixon 1992).
Therefore, a part of the energy assimilated, proportional to [Mathematical Expression Omitted], needs to be devoted to the building of the flight apparatus during larval development, after which the rest of the energy assimilated is partitioned in exactly the same way as in unwinged aphids.
Generally, for the same [Alpha], R, and [s.sub.0] (somatic birth size) values, the predicted adult size of winged aphids is smaller and the developmental time longer than for unwinged aphids.
Shrubs or subshrubs stout to trailing, stem winged to unwinged
. Leaves alternate; sessile to short-petiolate; blades simple to pinnately compound, with or without terminal tendrils, linear, subulate, lanceolate to ovate, pinnately to one-veined, margin entire to runcinate, sometimes revolute, glabrous to pubescent.
Based on the cladistic analysis by Anderberg (1994a) Enkianthus seems to have originally been shrubs with deciduous leaves, racemose inflorescences, camp anulate corollas, and winged seeds, whereas the more derived species possess coriaceous leaves, umbellate inflorescences, flowers with tubular or urceolate corollas, and unwinged