For each population, our goal was to quantify the variation in diapause-related traits among individuals from several families under two treatments of photoperiod and two treatments of prey that induce the full expression of variation in aestival diapause observed in previous studies (e.g., Tauber and Tauber, 1986).
Individuals undergoing aestival diapause were recognized by the following criteria: lack of reproduction and the assumption of a plump, waxy appearance, which indicates the lack of ovarian development and development of fat tissue.
Heterogeneity among familes in the proportional occurrence of aestival dispause was analyzed with three-way tables using log-linear models (unreplicated data) (Sokal and Rohlf, 1981).
-- Of the seven populations tested for responses to photoperiod, only the multivoltine population from eastern North America (IC) had no aestival diapause within any family under either constant long daylength or with an increase in daylength (Table 2).
Under constant long daylength (in the absence of prey), most western populations showed significant among-family heterogeneity in the incidence of aestival diapause ([two females and [two males]: PL, AT, TP; [two males] only: LS; G test, [Alpha] = 0.05) (Fig.
In the three-way analyses of the incidence of aestival diapause, all western populations combined, and two individual populations from the Sierra Nevada Range (AT, TP), showed significant photoperiod x family interactions in the incidence of aestival diapause, and both photoperiod and family had significant individual effects on the two populations from the Central Valley and foothill regions (DA, PL) (Table 2, Fig.
The two western populations from the Central Valley and foothill regions (DA and PL) had very low levels of aestival diapause whether aphids were present or not.
Visual assessment and three-way analyses indicated highly significant prey x family effects on the incidence of aestival diapause in three of these populations (SC, LS, and TP) (Table 2, Fig.
There are chapters on Dark Irish Fillies, Dark Irish Colts, Northern Horses, Older Horses, and I admired the assessment of a yet-unplaced three-year-old bay gelding called Aestival
, who cost pounds 100,000 as a yearling, has a best Racing Post Rating of 53 and a pedigree that makes last season's performances over five and six furlongs irrelevant, while the weight he will get to carry for his first race as a three-year-old, irresistible.