Bettina Erregger

Rare behavioral phenotypes—behavioral monsters—can challenge hypotheses about the evolution of the neural networks that drive behavior. In crickets, the diversity of song recognition behaviors is thought to be based on the modification of a shared neural network. We here report on a cricket with a novel resonant song recognition pattern that challenges this hypothesis. Females of the species Anurogryllus muticus respond to pulse patterns with the period of the male song, but also to song at twice the period. To identify the mechanisms underlying this multi-peaked recognition, we first explored minimal models of resonant behaviors. Though all of the three simple models tested (autocorrelation, rebound, resonate and fire) produced some kind of resonant behavior, only a single-neuron model with an oscillating membrane qualitatively matched the Anurogryllus behavior with regard to both period and duty cycle tuning. Surprisingly, the rebound model, a minimal model of the core mechanism for song recognition in crickets, fails to reproduce the preference for higher duty cycles observed in the behavior, questioning the universality of the core algorithm. However, the behavior is reproduced with a network model that contains all computations from the song recognition network of crickets, revealing the importance of an additional computation not part of the core mechanism: Following the core rebound mechanism in which post-inhibitory rebounds give rise to the resonant period tuning, feed-forward inhibition further shapes the tuning, resulting in the observed behavioral profile. Overall, this shows how unusual behavioral phenotypes can evolve by combining different nonlinear computations at the level of single cells and networks.

Although certain forms of parental care are relatively widespread phenomena among insects, within Orthoptera, parental care is rare. Short-tailed burrowing crickets (Anurogryllus spp.) are among the few members of this order for which extensive parental care has been documented. However, accounts of parental care in Anurogryllus have been largely under laboratory conditions, and observations of this behavior in the wild are rare. Herein we present photographic observations from a mountain slope in Honduras where we discovered an active Anurogryllus brood chamber where an adult female was tending her brood. We present these results in the context of parental care in insects and compare our observations with those reported in past literature published on Anurogryllus crickets' parental behavior.

Heteroptera, or true bugs populate many climate zones, coping with different environmental conditions. The aim of this study was the evaluation of their thermal limits and derived traits, as well as climatological parameters which might influence their distribution. We assessed the thermal limits (critical thermal maxima, CT_max, and minima, CT_min) of eight seed bug species (Lygaeidae, Pyrrhocoridae) distributed over four Köppen–Geiger climate classification types (KCC), approximately 6° of latitude, and four European countries (Austria, Italy, Croatia, Bulgaria). In test tubes, a temperature ramp was driven down to −5 °C for CT_min and up to 50 °C for CT_max (0.25 °C/min) until the bugs’ voluntary, coordinated movement stopped. In contrast to CT_min, CT_max depended significantly on KCC, species, and body mass. CT_max showed high correlation with bioclimatic parameters such as annual mean temperature and mean maximum temperature of warmest month (BIO5), as well as three parameters representing temperature variability. CT_min correlated with mean annual temperature, mean minimum temperature of coldest month (BIO6), and two parameters representing variability. Although the derived trait cold tolerance (TC = BIO6 − CT_min) depended on several bioclimatic variables, heat tolerance (TH = CT_max − BIO5) showed no correlation. Seed bugs seem to have potential for further range shifts in the face of global warming.

Sexual displays of acoustically signalling insects are used in the context of mate attraction and mate choice. While energetic investment in sound production can increase the reproductive success of the sender, this entails metabolic costs. Resource allocation into sexually selected, reproductive traits can trade off against allocation to naturally selected traits (e.g., growth, immunity) when individuals' energy budgets are limited. Estimating the magnitude of the costs invested in acoustic signalling is necessary to understand this trade-off and its influence on fitness and life-history. To compare the costs associated with acoustic signalling for two ensiferan species, we simultaneously took respiratory measurements to record the rate of CO2 production and used infrared thermography to measure the increase in thorax temperature. Furthermore, to identify what combinations of acoustic parameters were energetically costly for the sender, we recorded the calling songs of 22 different cricket and katydid species for a comparative analysis and measured their thorax temperature while they sang.Acoustic signalling was energetically costly for Mecopoda sp. and Anurogryllus muticus, requiring a 12- and 16-fold increase over resting levels in the CO2 production rate. Moreover, calling increased thorax temperature, on average, by 7.6 and 5.8°C, respectively. We found that the song intensity and effective calling rate, but not simply the chirp/trill duty cycle or the pulse rate alone were good predictors for the thorax temperature increase in males.