The ratio of males to females in a species is often considered to be relatively constant, at least over ecological time. Hamilton noted that the spread of "selfish" sex ratio-distorting elements could be rapid and produce a switch to highly biased population sex ratios. Selection against a highly skewed sex ratio should promote the spread of mutations that suppress the sex ratio distortion. We show that in the butterfly Hypolimnas bolina the suppression of sex biases occurs extremely fast, with a switch from a 100:1 population sex ratio to 1:1 occurring in fewer than 10 generations.

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Experientia 44 (1988), Birkh/iuser Verlag, CH-4010 Basel/Switzerland 423 17 Kupfermann, I., Carew, T. J., and Kandel, E. R., Local reflex, and central commands controlling gill and siphon movements in Aplysia. Development and modulation of bursting in the identified neuron RI5 of juvenile Aplysia. Soc. Neurosci. Abstr. 12 (1986) 952. 20 Nolen, T. G., and Carew, T. J., The cellular analog of sensitization emerges at the same time in development as behavioral sensitization in Aplysia. J. Neurosci. 8 (1988) 212-222. 21 Nolen T. G., Mindell, J. A., and Carew, T. J., Development ofneurotransmitters implicated in learning in Aplysia. Soc. Neurosci. Abstr. 12 (1986) 399. 22 Ohmori, H., Development of intrinsic burst generation in identified neuron R15 of Aplysia. Brain Res. 222 (1981) 383-387. 23 Rankin, C. H., and Carew, T. J., Development of learning and memory in Aplysia. II. Habituation and dishabituation. J. Neurosci. 7 (1987) 133-143. 24 Rankin, C.H., and Carew, T.J., Dishabituation and sensitization emerge as separate processes during development in Aplysia. J. Neurosci. 8 (1988) 197 211. 25 Rankin, C. H., Stopfer, M., Marcus, E. A., and Carew, T. J., Development of learning and memory in Aplysia. I. Functional assembly of gill and siphon withdrawal. J. Neurosci. 7 (1987) 120-132. 26 Rayport, S. G., and Camardo, J. S., Differential emergence of cellular mechanisms mediating habituation and sensitization in the developing Aplysia nervous system. J. Neurosei. 4 (1984) 2528-2532. 27 Stopfer, M., and Carew, T.J., Development of sensitization in the escape locomotion system of Aplysia. J. Neurosci. 8 (1988) 223-230. 28 Stopfer, M., Schuerman, G., and Carew, T. J., Development transition of locomotor programs in Aplysia californica. Soc. Neurosci. Abstr. 13 (1987) 1506. Mechanoafferent neurons innervating the tail of Aplysia. II. Modulation by sensitizing stimuli.

Free-flying individual Lasiurus cinereus semotus were observed as they foraged near incandescent lights on the island of Kauai, Hawaii. Two types of vocalizations were recorded from the bats: an echolocation–hunting signal with peak frequency of 27.8 kHz and an agonistic social signal, emitted while the bats were in aggressive pursuit of one another, with a peak frequency of 9.6 kHz. The tendency to vocalize agonistically increased with increased numbers of bats in the foraging area and increased as the density of insects available to the hunting bats decreased. Our observations suggest that the bats may gather echolocation information from their social signals. The bats at the site foraged under most weather conditions, including fog, moderate rain, strong winds, and temperatures as low as 13 °C. Groups of up to eight animals were common, although bats hunted in airspaces that were vigorously defended against other individuals. Small flies and small moths (< 10 mm body length) were the most common insects available as prey, but larger moths (16–20 mm) made up the bulk of the bats' diet. Moths larger than 20 mm were available but not fed on by the bats. This unique study site provides a rare opportunity to compare both prey availability to prey consumption in a population of bats. Our results suggest that this bat, at least on a short-term basis, exhibits a high degree of selectivity in its foraging, a behaviour similar to the mainland subspecies.

The authors apologise for this mistake and any inconvenience caused to readers. 4689The evolutionary arms race between insectivorous echolocating bats and moths has long fascinated biologists (Roeder, 1967;Fullard, 1998;Miller and Surlykke, 2001;Jones and Rydell, 2003;Waters, 2003). The primary purpose of the moth's simple ear -to detect bat echolocation callshas made this a particularly useful model for study (Fullard, 1988;Waters, 2003). The ears of moths have evolved as a direct result of selective pressure by bats; they are broadly tuned to the frequency ranges of sympatric insectivorous bat communities and inform the central nervous system to initiate erratic flight behaviours and/or stop flying (Fullard, 1988;Hoy et al., 1989). As part of the acoustic startle response, some species of tiger moths (family Arctiidae) produce clicks using thoracic tymbals that appear to deter attacks from nearby bats (Dunning and Roeder, 1965; Hirstov and Conner, 2005a). Many arctiid species contain sequestered or synthesized defensive chemicals (Rothschild et al., 1970;Weller et al., 1999;Nishida, 2002) unpalatable to a variety of predators, including bats (Dunning, 1968;Coutts et al., 1973;Goss, 1979;Boppré, 1990;Hristov and Conner, 2005b).The clicks of arctiid moths have been proposed to function as acoustic aposematic signals (Blest et al., 1963;Dunning and Roeder, 1965;Dunning, 1968;Hristov and Conner, 2005a) and as signals that interfere with information processing facilitating escape, by startling the bat (deimatism) and/or jamming echolocation (Bates and Fenton, 1990;Fullard et al., 1979Fullard et al., , 1994Miller, 1991;Masters and Raver, 1996;Tougaard et al., 1998Tougaard et al., , 2004. These functional hypotheses are not mutually exclusive although they are often portrayed as such (e.g. Surlykke and Miller, 1985;Fullard et al., 1994;Waters, 2003; Hristov and Miller, 2005a). Until recently (Hristov and Conner, 2005a), all laboratory studies had used (1) synthetic bat echolocation calls and stationary moths, (2) synthetic arctiid clicks and stationary bats or (3) free-flying bats capturing mealworms while synthetic clicks were broadcast >1·m away from the prey trajectory (see Waters, 2003 and We studied the efficiency and effects of the multiple sensory cues of tiger moths on echolocating bats. We used the northern long-eared bat, Myotis septentrionalis, a purported moth specialist that takes surface-bound prey (gleaning) and airborne prey (aerial hawking), and the dogbane tiger moth, Cycnia tenera, an eared species unpalatable to bats that possesses conspicuous colouration and sound-producing organs (tymbals). This is the first study to investigate the interaction of tiger moths and wild-caught bats under conditions mimicking those found in nature and to demand the use of both aerial hawking and gleaning strategies by bats. Further, it is the first to report spectrograms of the sounds produced by tiger moths while under aerial attack by echolocating bats. During both aerial hawking and gleaning trials, all muted C...

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