Experiments on sexual isolation between Chilean and European strains ofDrosophila subobscura

Summary Males and females of Chilean strains ofDrosophila subobscura exhibit a pronounced tendency toward homogamic mating. This tendency shows a clear relation to the distance between the geographic localities from which the respective strains came. Nevertheless, when the Chilean flies are confronted with European strains, the ethological isolation is observed in some cases but not in others, depending on the geographic origin of the strains.Acknowledgments. This work has been partially supported by grants from the Univ. of Chile (Project B 729-8345) and PNUD/UNESCO (RLA 78/024). We are most grateful to Prof. D. Sperlich of the University of Tübingen who provided theD. subobscura strains from Tübingen and Sicily, and Prof. A. Prevosti from the University of Barcelona and R. de Frutos from the University of Valencia who provided the strains of Mallorca and Almería. We are finally obliged to Mr E. Zárate for his technical assistance.     

The role of assortative mating among age-classes inDrosophila melanogaster: preliminary results

Summary A series of experiments on age-related mating success and productivity provides evidence for assortative mating among three out of four age-classes inD. melanogaster. The preferred mating does not always result in the highest productivity. Three age classes of males contribute to reproduction while only females of the youngest age-class are involved. The progeny size is more affected by the age of the females than that of males. It is assumed that these findings must have important implications for generation overlap in natural populations.     

The evolutionary history ofDrosophila buzzatii. V. Differential survivorship onOpuntia betweenD. buzzatii andD. serido

Summary Survival time ofDrosophila buzzatii adults on anOpuntia (prickly pear) medium was significantly longer than that of its nearest relativeD. serido. A significant difference was also found betweenD. buzzatii adults from two experimental populations, one of them fed onOpuntia rots for more than two years and another one kept on standardDrosophila medium for the same period of time. These results suggest that adult selection may be taking place in cactiphilicDrosophila in their natural habitats and could be responsible for the niche differentiation betweenD. buzzatii andD. serido.This work has been supported by the Comisión Asesora de investigación Científica y Técnica, Spain, by funds to project 4514/79 awarded to the third author.     

Genetic load and effective size of natural populations ofDrosophila melanogaster in Korea

Summary The effect of 750 second chromosomes ofDrosophila melanogaster on viability was studied. 19.3% of them proved letal or semilethal (=drastics) in homozygous condition. Compared to data obtained in previous years at the same sampling site, a significant frequency decrease of drastics during the past decade could be observed. The dynamic processes taking place in the Korean wild populations ofD. melanogaster are discussed.Acknowledgment. This work was supported by a research grant from the Korean Science and Engineering Foundation.     

The effect of DDT on DNA replication in the larval salivary gland cells ofDrosophila melanogaster

Summary The inhibitory effect of DDT on the initial stage of the DNA replication process in polytene chromosomes of larval salivary gland cells ofDrosophila melanogaster was investigated and possible mechanisms for the inhibition are discussed.     

Changes in patterns of ecdysteroid secretion by the ring gland ofDrosophila in relation to the sterol composition of the diet

Summary Brain-ring glands fromDrosophila larvae reared on a defined diet containing campesterol (24-methyl-cholesterol) as the major sterol, secreted-in addition to ecdysone-a compound identified previously as a 24-methyl analogue, 20-deoxy-makisterone A. Using ergosterol or cholesterol as the sterol component of the diet, only ecdysone was detectable in cultures of brain-ring glands.     

Genetic basis of some morphological differences between temperate and equatorial populations ofDrosophila melanogaster

The genetic basis of three morphological traits (ovariole number, sternopleural bristle number and wing length) ofDrosophila melanogaster has been investigated in natural populations that show great differences in these traits, i. e. Bordeaux (France) and Loua (Congo). F1 and F2 crosses, and chromosome substitutions between these two populations, were analysed. Maternal and/or X chromosome effects were found for sternopleural bristle number and wing length. For all traits, significant effects from each of the three chromosomes were found, but in general only one or two chromosomes had a major effect. Moreover, in all cases significant interactions between chromosomes were observed, suggesting the existence of epistatic effects. Our results are discussed and compared to those obtained from the analysis of selected laboratory strains.     

The endogenous regulation of mosquito reproductive behavior

Summary Most female mosquitoes require a meal of blood that provides protein for egg maturation. For reproduction to occur, two behavioral sequences are essential. One is concerned with finding a host for the blood meal and the other in finding a site on which to lay the eggs that result. Stimuli from both hosts and oviposition sites initiate the reproductive behaviors of host-seeking and pre-oviposition, respectively, that are discussed in this review. After sensory receptors perceive these stimuli, the central nervous system must integrate the information and associate it with a biologically appropriate response. Host-seeking appears to be the default behavior, expressed whenever host stimuli are present. However, if the female is successful in locating a host and ingesting blood, subsequent host-seeking is inhibited when the meal distends the abdomen above a certain threshold. Host-seeking inhibition continues during egg development as a result of a humoral mechanism even after the blood volume has been reduced by digestion. At the time when eggs are maturing and host-seeking is inhibited, pre-oviposition behavior predominates if the central nervous system receives oviposition site stimuli. This behavior is also initiated by a humoral factor. Several physiological states, including insemination, age, and nutrition, can modulate both host-seeking and pre-oviposition behaviors.     

Sexual behavior without adult morphogenesis inLocusta migratoria

Summary Injection of azadirachtin into young Vth (=last) instarLocusta hoppers inhibits molt and a considerable portion of the animals survice for more than 40 days as over-aged nymphs; in contrast, the duration of the Vth instar is 8–10 days in normal controls. Males of over-aged nymphs exhibit adult sexual behavior, and injection of juvenile hormone intensifies this behavior. The results demonstrate that the terminal molt leading to morphogenetic adult differentiation is not necessary for an adult behavioral pattern to develop, and/or to become overt, in a hemimetabolous insect.We thank Prof. H. Rembold for a generous gift of azadirachtin and Mr Y. Toren for keeping the locust culture.     

Photoperiodic regulation of mating behaviour in the linden bug,Pyrrhocoris apterus,is mediated by a brain inhibitory factor

Active inhibition of mating behaviour in a male insect is reported here for the first time. InPyrrhocoris apterus L. (Heteroptera), the most important inhibitory pathway runs from the pars intercerebralis (PI) of the brain and does not pass through the corpora allata. The inhibitory activity of the PI is promoted by short day conditions and suppressed by long days. As the effect of photoperiod is delayed, transfer procedures enabled us to record daily rhythms in mating behaviour during short days. While the extirpation of the PI results in a discrete phase shift of the long day rhythm, there is a much less significant phase shift after this operation during short days. Thus the PI has been shown to mediate the effect of photoperiod on both the inhibition and the rhythm of mating behaviour.     

Escape behavior in the cockroach: Distributed neural processing

Summary Escape reactions are often considered to be among the simplest behaviors. The nerve circuits guiding these reactions are also generally thought to be simple. For instance, in several species a single interneuron is sufficient to trigger normal escape. The evasive response of the cockroach, however, appears to be more complex both behaviorally and physiologically. In this review, several complications of the behavior are pointed out, based on a recent computer-graphic analysis of the leg movements. Next described is the cooperative role of several interneurons-not just one-in evoking an escape turn away from the stimulus. A model of this multicellular code for stimulus direction is then presented that correctly predicts the turning behavior under many different experimental conditions. Finally, an overall scheme of the information processing for escape behavior is presented.     

Torus shaped bands at the 2R telomere region and at the region 68 of the salivary gland chromosomes ofDrosophila auraria

Summary The telomere of the 2R arm of the salivary gland chromosomes ofD. auraria exhibits a definite toroidal structure in routine squashed preparations, stained either by propionic orcein-carmine or by fluorescent dyes. There is evidence that a band (or bands) of region 68 (possibly homologous to that ofD. melanogaster) of the 3L chromosome arm also exhibits a toroidal structure. These toroids are associated with heterochromatin, but it is not certain that they are themselves heterochromatic.Acknowledgments. This work was supported by a grant from Volkswagenwerk-Stiftung to C.D.K. The outstanding technical assistance of Ms G. Karamanlidis is acknowledged.     

Pupation-temperature range in 12Drosophila species from different ecological backgrounds

Summary A comparison of pupation-temperature range was made in the laboratory on a temperature gradient (3–38°C) using 12 species ofDrosophila representing four species groups and four different ecological backgrounds (temperate-montane forest:virilis group; desert;repleta group; cosmopolitan:melanogaster group; tropical forest:willistoni group). Within groups, differences are found which usually reflect species' distributions. Comparisons of species' mating-, oviposition- and pupation-temperature ranges reveal that pupation most-often occurs at temperatures beyond those for mating and oviposition. Each species reflects a different combination of temperature effects. Individual species have different temperature-limits for mating, oviposition and pupation. Temperatures permissive for one response are not predictive of limits on other responses. Among species, temperature can affect a particular response differently. Within groups, species differences can be at high and/or low temperatures for any response, and temperature effects among closely related species can manifest themselves in one, or any combination of responses. One cannot predict which responses will be most and least limited, or at which end of the temperature scale a response will be most limited. Among groups,common, but notabsolute temperature ranges generally correspond to the geographic distributions and ecological backgrounds of the species triads. The evaluation of temperature effects on species, based on a single activity, may not be adequate for predicting adaptive strategies.     

Cattle grazing behavior regulates tick populations

Summary Analysis of field population data showed that host-seeking larvae of the tickBoophilus microplus were less successful in attaching to their hosts when larval densities were high. Experimental results showed that cattle hosts detected and avoided high densities of larvae in pasture. The finding reveals a previously unknown population-regulating mechanism for ticks, which are important pests of livestock.Acknowledgment. The authors wish to thank G. Maywald, D. Stegeman, R. Tozer, A. Voll, G. Milne and J. Osborne who helped with the observations. The Australian Meat Research Committee (AMRC) and the Australian Centre for International Agricultural Research (ACIAR) provided some financial support for the project and A. Edwards assisted greatly with the photography.     

The sensitive period for yellow phenocopy induction inDrosophila melanogaster

Summary Yellow phenocopies ofDrosophila melanogaster were produced by raising larvae on -DMT contaminated media. Using a survivorship test, the sensitive period for phenocopy induction was found to occur during the third larval instar of development, with increased survivorship at 1% -DMT compared with lower concentrations. It was also found that treatment with -DMT significantly slowed development. These findings are related to the relevant morphological and behavioral developmental pathways and to phenocopy induction.Publication No. 35 from the Evolutionary Genetics Laboratory, University of Auckland.Acknowledgments. We thank the New Zealand Entomology Society for a grant from their Anniversary Fund to R. D. Newcomb and the University Grants Committee, Research Grant No. 394.597 to D.M. Lambert.     

Synthesis of a ubiquitously present new HSP60 family protein is enhanced by heat shock only in the Malpighian tubules ofDrosophila

A homologue of the chaperonin protein of the HSP60 family has not been shown so far inDrosophila. Using an antibody specific to HSP60 family protein in Western blotting and immunocytochemistry, we showed that a 64-kDa polypeptide, homologous to the HSP60, is constitutively present in all tissues ofDrosophila melanogaster throughout the life cycle from the freshly laid egg to all embryonic, larval and adult stages. A 64-kDa polypeptide reacting with the same antibody in Western blots is present in all species ofDrosophila examined. Using Western blotting in conjunction with³⁵S-methionine labeling of newly synthesized proteins and immuno-precipitation of the labeled proteins with HSP60-specific antibody, it was shown that synthesis of the 64-kDa homologue of HSP60 is appreciably increased by heat shock only in the Malpighian tubules, which are already known to lack the common HSPs.     

The isolation,identification and synthesis of the alarm pheromone ofVespula squamosa (Drury) (Hymenoptera: Vespidae) and associated behavior

Summary A material that elicits alarm and attack behavior byVespula squamosa (Drury) workers was isolated from venom extracts and identified by spectroscopic methods as N-3-methylbutylacetamide. This compound elicited attack responses from worker wasps identical to those responses observed when venom was applied at the same dosage. This is the first behavioral role reported for this compound.The authors thank E. Adamak, R. Murphy and F. Takken for technical assistance. This article reports the results of research only. Mention of a proprietary product does not constitute an endorsement or the recommendation for its use by USDA.