In two races of European corn-borer moths (ECB), the E-race females emit and males respond to 99:l sex pheromone blend of (€)/(a-11-tetradecenyl acetates, whereas the Z-race females and males produce and respond to the opposite 3:97 pheromone blend of (€)/(a-11-tetradecenyl acetates, respectively. We previously have shown that female production of the final blend ratio i s under control of a major autosomal locus but that the sequence of male upwind flight responses to the blend i s controlled by a sex-linked (Z-linked) locus. This sex-linked control of behavioral responses in crosses of E and Z ECB now is confirmed by use of sex-linked TPI (triose phosphate isomerase) allozyme phenotypes to determine the origin of the sex chromosomes in F2 populations.F1 males from reciprocal E x Z crosses generate similar behavioral-response profiles in wind-tunnel studies, with moderate numbers responding to the Z pheromone and intermediate blends (35%-65% Z), but very few responding to the E pheromone. The F2 behavioral-response profiles indicate that they are composed of 1 :I mixtures of hybrids and paternal profiles. Analysis of TPI allozyme differences allowed us to separate male F2 populations into individuals whoseZchromosomes both originated from their grandfathers, and individuals who had one Z chromosome originating from each grandparent. With these partitioned F2s, the TPI homozygotes exhibited behavioral-response profiles very much like their grandfathers, whereas the TPI hybrids produced response profiles similar to their heterozygous F, fathers. These results demonstrate incontrovertibly that the response to sex pheromone in male ECB is controlled by a sex-linked gene that i s tightly linked to the TPI locus and therefore i s independent of the locus controlling pheromone blend production in females.Acknowledgments: The authors thank M.L. Hessney for rearing the insects used in these studies and J.P. Nyrop (Department of Entomology, NYSAES) and J. Barnard (Laboratory Director of Computer Services, NYSAES) for invaluable advice regarding statistical analysis. We are also indebted to M.R. Nolan and S. Kresovich (Germplasm Resources, National Clonal Repository, NYSAES) and N.F. Weeden (Department of Horticultural Sciences, NYSAES) for advice and encouragement regarding electrophoresis techniques.

Abstract. In genetic studies on the sex pheromone communication system of two races of European corn borer, which use opposite pheromone blends of the E and Z compounds, it was found that antennal olfactory cell response amplitudes to the two compounds were controlled by an autosomal factor, whereas behavioral responses to the blends were controlled by a sex-linked locus. Because of the difference in genetic controls, it was postulated that some unusual males would be produced in F2 crosses between these two races. These unusual males would have antennal olfactory cells that respond as the Z-race males, but would respond behaviorally to the E blend. The present studies combined behavioral studies in a flight tunnel and single cell electrophysiological studies to show that these unusual males do indeed exist. These findings show that the spike amplitude of peripheral olfactory cells is not important in regulating species-or race-specific pheromone responses, as compared to some central nervous system factor assesses the spike frequencies from different pheromone-component-specific cells on the antenna. This factor seems to be essential in governing the pheromone-blend specific behavioral responses of male moths.

The pheromone-mediated flight behavior of male Oriental fruit moths was observed in the field to test the hypothesis that male activation far downwind of a female is initiated by the major, or most abundant, component of the pheromone blend. Males responded at significantly greater distances to the three-component pheromone blend produced by females than to the major component alone or to either binary mixture containing the major component and one minor component. These results support the alternative hypothesis that the active space of a multicomponent pheromone is a function of male perception of the female-released blend of components, rather than of the major component alone, and that so-called minor components have a greater impact on male behavior farther downwind of a female than previously thought.

ABSTRACT. The response specificity of male Oriental fruit moths, Grapholita molesta (Busck) and pink bollworm moths, Pectinophora gossypiella (Saunders), to different blends and doses of pheromone is altered dramatically by temperature. When acclimated and tested in a flight tunnel at 20oC males of both species exhibit a high degree of specificity, with peak response levels occurring to a narrow range of blend‐dose combinations close to the natural blend. When tested at 26oC, however, males exhibit a significantly lower degree of specificity, with peak response occurring to a broader range of treatments. The change in response specificity results from shifts in behavioural threshold effects influencing plume orientation and initiation of upwind flight, as well as from arrestment of upwind flight, occurring later in the flight sequence. The observed changes in male behaviour suggest that the effect of temperature is directly on neural pathways involved in the perception of odour, and not simply the result of an increase in motor activity or a significant change in the release rate of the pheromone. The results support the threshold hypothesis for pheromone perception (Roelofs, 1978) as a general principle in the Lepidoptera, but also show that the degree of response specificity can be significantly affected by temperature.

No abstract

Experiments were conducted to determine whether the biogenic amines octopamine (OA) and 5-hydroxytryptamine (5-HT) exert modulatory effects on pheromone responsiveness and random locomotor activity in male gypsy moths. When injected into males, OA significantly enhanced sensitivity to pheromone, while 5-HT enhanced general locomotor activity, results that were very similar to those previously shown for the cabbage looper. Maximal effect of the amines, however, was observed when injection occurred just prior to the onset of scotophase, rather than photophase, as we had originally hypothesized for this diurnallyactive insect. Male gypsy moths also displayed a prominent scotophase response, with sensitivity to pheromone greater in the scotophase compared with photophase, but with the level of random locomotor activity lower in scotophase than in photophase. The upwind flight behavior of males to a pheromone source in a wind tunnel, as well as the time spent at the source, were also significantly different in the two light regimes. Furthermore, when exposed to a 1 h scotophase (instead of the normal 8), or to continuous dark conditions, while males exhibited response to pheromone and locomotor activity during the same scotophase and photophase periods as observed in a 16:8 1ight:dark cycle, the levels of response, as well as qualitative aspects of the upwind flight behaviors in both periods were a function of the light intensity, Our combined results suggest that male gypsy moths display a bimodal rhythm of locomotor and pheromone response over the die1 cycle, with light intensity and scotophase onset providing critical cues for the expression of behaviors, as well as the modulatory action of the amines. GI 1992WiIey-Liss, inc.Acknowledgments: We thank Kathy Poole for help in rearing the insects, and Geoffrey Rule for preparation of the pheromone standards. We are also grateful to C. P. Schwalbe (Otis USDA-APHIS Methods Development Center) for supplying the insects. We are especially rateful to Drs. Ralph Chartton and Jeremy McNeil, as well as an anonymous reviewer, for tieir thorough and critical comments.

In the present study male redbanded leafroller (Argyrotaenia velutinana), cabbage looper (Trichoplusia ni), and Oriental fruit moths, (Grapholita molesta), were tested in a flight tunnel to (1) the major pheromone component, (2) theZ/E pheromone component mixtures for Oriental fruit moth and redbanded leafroller, (3) and the female-released blends, over a series of dosages. Experiments were designed to test the hypothesis that male response downwind of a female is initiated by the major component and that minor components function only to elicit behaviors close to the female during close-range approach and courtship. The results did not support this hypothesis, but rather showed that males initiated upwind flight in significantly higher percentages to the complete blends of components, at all dosages, compared to single components or partial blends. Addition of minor components also signficantly enhanced male perception of the major component at lower dosages, resulting in completed flights to dosages of the major component that alone did not elicit any upwind flight. Our results support the concept that minor components function to enhance male sensitivity to the pheromone, and the specificity of the signal. Our results also support the hypothesis that the active space of the pheromone is a function of the upper and lower concentration thresholds for the blend of components, and not simply for the major component.

Abstract. Unlike the narrow response windows exhibited by the parent races, hybrid male European corn borers resulting from crosses of the E and Z races respond to a wide range of sex pheromone blends. The F~ response profile consists of some individuals that respond to both the Z pheromone and the 65:35 E/Z blend produced by Fa females. Some F~ males fail to respond to any blend and some do not respond as broadly as others. The hybrid male populations, however, are not tuned optimally to the pheromone blend produced by F 1 females and there is no coupling of F~ blend production and response.Key words. European corn borer; Ostrinia nubilalis; sex pheromone polymorphism; interracial hybrids; F1 male-response profiles; flight tunnel.The European corn borer (ECB), Ostrinia nubilalis, exhibits polymorphisms of important elements of its sex pheromone communication system. Within the species are populations, in both Europe and North America, that respond to and produce unique pheromone blends, which in turn affords considerable genetic isolation to members of these populations 1-5. The within-race female-pheromone production and male-response profiles have been extensively studied for three races occurring in New York State, USA. These races, while morphologically indistinguishable, have distinct differences in voltinism (bivoltine vs univoltine) and in their sex pheromone system (E vs Z) 6-8 as well as some less pronounced differences in host plant range and susceptibility to insecticides 9-11. These races are abbreviated BE, BZ, and UZ to denote their most important differences. In the Z races, females produce a blend of 3 : 97 (E)-I 1-tetradecenyl acetate/(Z)-ll-tetradecenyl acetate (Ell-14: OAc/Zll-14 :OAc) as the sex pheromone, with peak male response occurring to this ratio. A second blend of 99:1E/Z11-14:OAc's is utilized as the sex pheromone by members of the E race 6,12-14. A series of studies have elucidated the genetic bases of the sex pheromone communication system polymorphisms. The female-blend ratio is controlled by an autosomal factor that exhibits incomplete dominance in hybrid females resulting in a sex pheromone of approx. 65:35 E/ZI 1 -14: OAc's 13-14. The behavioral response of the males to appropriate pheromone stimuli in a flight tunnel has been shown conclusively to be under control of sexlinked genetic elements (males are the homogametic sex)14, is. The response profile of male ECB from the Z races is highly canalized with very few individuals responding to blends other than those close to the natural 3 : 97 E/Z ratio. E males, on the other hand, exhibit peak response to the natural blend of 99:1 E/Z, but with significant numbers also responding to the hybrid blend as well as 50:50 and 35:65 E/Z 14'1~. Behavioral responses of parent and hybrid males are summarized in figure 1. Recently, there have been several Studies undertaken to describe the interaction of Z and E races in sympatry16, tT. A difficulty in describing these interactions stems from incomplete characterization of the hybrid male ...