A .~ 4 .6 ,8 1,o mm j 0 00~ 000 0 Ol 9 ~176 v o amputtory org. 3 O 9 tuberous organ " ! ' I n mormyromQLst 0 m ~ 9 .2- 1.0 mr'T1 .G .8 1.0 1.2 1./.ram r i i O i .... O ~ O n n 0 0 ~I ,2 ~ 2 ~ o ~ "1~ e~ a ~ e e ~ o e a ~ 0 Fig. 3. Distribution of electrosensory organs in two sections of skin excised after 42 days (A) and 112 days (B, cluster of Fig. 2 B) fol- lowing nerve deflection. Dimensions of the histologically examined sections of skin in mm the photographed area (Fig. 2A). It is unclear why a maximum of 90 out of an expected 350 organs were induced in the observed area and why the pro- portion of the three organ types in the newly induced population is different from the original innervated popula- tion (note only one mormyromast in Fig. 3 A). The spatial distribution of the newly induced organs of different types with- in a clusterappearsrandom (Fig. 3). This indicates that every region in the observed sensory skin area is equally capable of differentiation into the re- ceptor type which is coded by the or- gan-controlling substance specific to the regenerated nerve fiber. In Fig. 3 A, accumulation of ampullary and tuber- ous organs is found in the upper and lower half of the cluster, respectively. There is a tendency for tuberous organs to accumulate in the upper right and lower left of the skin section of Fig. 3 B. A reasonable explanation for this phe- nomenon may be that the afferent fibers belonging to one organ type are grouped within the nerve trunk. Supported by the DFG. Received July 9, 1987 1. Bailey, S.W.: J. Exp. Zool. 76, 187 (1937) 2. Roth, A.: Naturwissenschaften 72, 380 (1985) 3. Roth, A. : ibid. 73, 264 (1986) 4. Szabo, T., Fessard, A.: Handbook of Sensory Physiology, Vol III/3, p. 59 (ed. A. Fessard). Berlin-Heidelberg-New York: Springer 1974 5. Harder, W.: Z. vergl. Physiol. 59, 272 (1968) 6. Karnovsky, M.J.: J. Cell Biol. 27, 137 A (1965) Naturwissenschaften 74, 497-499 (1987) 9 Springer-Verlag 1987 Inheritance of Olfactory Response to Sex Pheromone Components in Ostrinia nubilalis B.S. Hansson and C. L6fstedt Department of Ecology, University of Lund, S-223 62 Lund W.L. Roelofs Department of Entomology, New York State Agricultural Experiment Station, Geneva, N.Y. 14456, USA Two pheromone strains of the Europe- an corn borner (Ostrinia nubilalis), oc- cur sympatrically in some areas of Eur- ope and North America [1]. In the so- called Z-strain the females produce, and the males are attracted by, a 97:3 mixture of (Z)-I 1- and (E)-J 1-tetrade- cenyl acetate, whereas the E-strain uti- lizes the inverse blend [2]. F 1 hybrids produce and prefer an intermediate blend, 35:65 [3]. We now report that males can be distinguished by their electrophysiological olfactory response to the pheromonecomponents. Dis- tinct E-, Z-, and intermediary male re- action patterns were found in the F2 generation and in the maternal and pa- ternal backcrosses. The frequencies ob- served correspond to those expected if male pheromone response is deter- mined by one Mendelian gene with two alleles, as was earlier reported for the female pheromoneproduction in O. nubilalis [3]. The E- and Z-strains are morphologi- cally indistinguishable, but according to electrophoretic isoenzyme analysis the strains do not interbreed freely [4]. In addition to the pheromone polymor- phism, North American populations of t h e European corn borer also have a variable number of generations per year [5]. Recent investigations in New York State documented the presence of three population types in this area: a bivoltine E (BE), a bivoltine Z (BZ), and a univoltine Z (UZ) [6]. These three races have all been established as cultures in the USA laboratory. We re- corded the electrophysiological re- sponses to (Z)-JJ- and (E)-ll-tetrade- cenyl acetate (Zll- and EI J-14:OAc) from single olfactory sensilla on the an- tennae of males from these three cul- tures, and from their hybrids. Initially we found that it was possible to distin- guish the reactionpatternsof males from the Z- and E-types with bivoltine life pattern. Furthermore, sons from crosses between these races showed a third reaction pattern (Fig. 1 A). The males were distinguished by having ol- factory cells responding differently to the sex pheromone components. In the E-males the amplitude of the Z-cell ac- tion potential was about 35% of the sum of the amplitudes of the Z- and E-cells. This measure was calculated to provide a quantitative estimate of the sensillarcharacteristics of individual males. In the Z-males it was about 65% and in the hybrids it was 50%. Males from the UZ population conformed to the pattern observed in the BZ popula- tion. Both the Z- and E-type insects also responded with a very small spike Naturwissenschaften 74 (1987) 9 Springer-Verlag 1987 497