Nicrophorine beetles (Nicrophorus and Ptomascopus spp.) use small carcasses as a food source for young, a breeding ecology distinct from other silphid beetles. While adaptations to the use of small carcasses are well known for Nicrophorus (emitting sex pheromone, burying, rounding and removing hair from carcasses, regulating brood size, regurgitating to young, and preventing predation), there is little information regarding its sister group, Ptomascopus. Like Nicrophorus, Ptomascopus morio males emit pheromone to attract females. In the absence of carrion competitors Ptomascopus morio parents were found to stay with a carcass and their brood for up to 10 days. We tested six hypotheses to examine whether young bene®t from this long period of parent±offspring contact. (1) There was no evidence that parents buried or otherwise pre-empted carcasses to reduce competitive pressure. (2) We found no evidence that parents in¯uenced the decomposition of the carcass. This was supported by experimental manipulations in which brood production (number of larvae and total brood mass) was no greater on carcasses on which parents were present than on carcasses not`prepared' by parents. In addition, the carcass was not rounded and little hair was removed by the adults. (3) The presence of parents bene®ted the brood by reducing the negative effects of competition with carrion¯y larvae. This likely resulted from predatory feeding by adult beetles. (4) Females adjusted clutch size to the size of the carcass. Parents, however, did not make a second adjustment in brood size after young reached the larval stage (®lial cannibalism), as occurs in Nicrophorus. (5) Although parents were observed to open feeding holes in the carcass, this was not necessary for normal larval growth and survival. Parents were not observed to feed young directly by regurgitation. (6) Lastly, parents did not reduce predation on their brood when a conspeci®c intruder was present. These ®ndings suggest that after the female parent adjusts clutch size to the size of the resource, the only parental bene®t is clearing the carcass of¯y larvae. Other differences with Nicrophorus include an extended period of oviposition (5 days) and less pronounced changes in ovarian mass and juvenile hormone titers in response to discovery of a carcass. In a ®eld experiment in Kyoto, Japan, 17 of 21 broods of N. concolor during August contained larvae of P. morio. Mixed Nicrophorus±Ptomascopus broods were less common at other times of the year and when N. quadripunctatus occupied carcasses. In the laboratory, P. morio was able to parasitize 19 of 20 broods of N. concolor. The pattern of oviposition, the absence of explicit parental behaviours, and the interactions with N. concolor in the ®eld suggest that Ptomascopus morio is a brood parasite of Nicrophorus.
-Mating behaviour and associated songs were compared between 2 sympatric congeneric species, Nezara antennata and N. viridula, between which interspecific mating was known to occur under natural conditions. The fundamental sequence of mating behaviour for these species was the same. Three kinds of songs were recorded from each sex of N. antennata. For N. viridula, 4 kinds of male songs and 3 kinds of female songs were recorded. The songs which corresponded with definite behavioural bouts were distinct between these species. Some consideration was made as to why interspecific differences in the songs did not sufficiently engender ethological isolation. In addition, some geographic variations in the songs were shown among Yugoslavian (~okl et al. 1972), American (Harris et al. 1982) and Japanese populations of N. viridula.These variations were relatively inconspicuous when compared with the interspecific differences from N. antennata.
Molecular phylogenetic relationships among 25 species of the wood-feeding cockroach belonging to the genus Salganea Stål (Panesthiinae; Blaberidae) in Southeast Asia were analyzed based on the DNA sequence of the complete mitochondrial cytochrome oxidase II (COII) gene. Most basal relationships among species of Salganea are poorly resolved by both neighbor-joining and nonweighted parsimony analyses, suggesting the possibility of a hard polytomy due to a rapid and potentially simultaneous radiation early in the history of the genus. For more apical relationships, however, some interesting phylogenetic relationships were recognized. The monophyly of the two species groups, morio and foveolata, the former of which is distributed mainly in the Sunda lands (containing the Malay Peninsula, Sumatra, Java, and Borneo), whereas the latter is Sulawesi endemic, was strongly supported. Based on the inferred phylogenetic patterns and recent palaeogeographic scenario for Southeast Asia, it is suggested that a radiation of Salganea species occurred in Southeast Asia presumably in the early Tertiary, and several barriers against dispersal and gene flow, such as the formation of straits or high mountains, have arisen from the middle Tertiary.
Abstract. 1. Under natural conditions in Kyoto, Japan, the reproductive activities of Nicrophorus quadripunctatus Kraatz (Coleoptera: Silphidae) decreased in summer and the species showed a bimodal life cycle.2. In the laboratory, most adult pairs raised at 20 C under a LD 12:12 h regime reproduced when provided with a piece of chicken. In adults raised at 20 C under a LD 16:8 h regime, however, both reproductive behaviour and ovarian development were reduced. It is concluded that these adults entered a reproductive summer diapause.3. High temperature (25 C) also suppressed the reproductive behaviour even under a favourable LD 12:12 h regime. In the field, therefore, adults reduce their reproductive activity in summer because of diapause induced by long-day photoperiods and direct inhibition of reproduction by high temperatures.4. When the temperature was changed from 20 C to 25 C immediately after hatching of larvae, they reached the wandering stage in 95% of adult pairs. When the temperature was changed from 20 C to 25 C immediately after oviposition, however, no larvae hatched in 85% of pairs. Egg mortality was significantly higher at 25 C than at 20 and 22.5 C; no eggs hatched at 27.5 C. The physiological mechanisms for reducing reproduction probably prevent the beetles from inefficient oviposition in summer.
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