Calling,Courtship, and Condition in the Fall Field Cricket,Gryllus pennsylvanicus

Theoretically, sexual signals should provide honest information about mating benefits and many sexually reproducing species use honest signals when signalling to potential mates. Male crickets produce two types of acoustic mating signals: a long-distance mate attraction call and a short-range courtship call. We tested whether wild-caught fall field cricket (Gryllus pennsylvanicus) males in high condition (high residual mass or large body size) produce higher effort calls (in support of the honest signalling hypothesis). We also tested an alternative hypothesis, whether low condition males produce higher effort calls (in support of the terminal investment hypothesis). Several components of long-distance mate attraction calls honestly reflected male body size, with larger males producing louder mate attraction calls at lower carrier frequencies. Long-distance mate attraction chirp rate dishonestly signalled body size, with small males producing faster chirp rates. Short-range courtship calls dishonestly reflected male residual mass, as chirp rate and pulse rate were best explained by a curvilinear function of residual mass. By producing long-distance mate attraction calls and courtship calls with similar or higher effort compared to high condition males, low condition males (low residual mass or small body size) may increase their effort in current reproductive success at the expense of their future reproductive success, suggesting that not all sexual signals are honest.     

Positive Relationship between Signalling Time and Flight Capability in the Texas Field Cricket, Gryllus texensis

A trade‐off between dispersal ability and reproduction is generally thought to explain the persistence of wing dimorphism in insects, although this trade‐off has received minimal attention in male insects. Research on male sand cricket, Gryllus firmus, supports the trade‐off hypothesis insofar as flight capable cricket’s spend significantly less time signalling for potential mates than their flightless counterparts. By contrast, here I show that this expected trade‐off between signalling time and wing dimorphism does not exist in a male congener, the Texas field cricket (Gryllus texensis). In G. texensis, flight capable males signal twice as often as flightless males. Thus, unless male G. texensis express trade‐offs between dispersal ability and other, presently unmeasured components of reproduction, the trade‐off hypothesis may not explain the persistence of wing dimorphism in all male insects.     

Family Effects on Antipredator Behavior in the Field Cricket, Gryllus Integer

Most animals have antipredator mechanisms. These may include a variety of behaviors. One such behavior is “freezing”, i.e. becoming immobile in response to a predator. This paper is focused on freezing behavior in a species of field cricket, Gryllus integer. We studied this behavior in both nymphs and adults, and looked for family effects, as well as the effects of sex. Our research shows that there are no family effects in nymphs, but there are family effects in adults. No sex differences occur between the sexes at either stage of development. Because all of the crickets were reared under identical conditions in the laboratory, such family effects are likely due to genetic effects, maternal effects, or both.     

Agonistic Displays and the Benefits of Fighting in the Field Cricket, Gryllus bimaculatus

Fighting is often composed of discrete agonistic displays. Few studies have partitioned fighting behavior into its component agonistic displays and evaluated the relationships between the frequency of the displays and the potential benefits of fighting, particularly mating success. In this study, we quantified the frequency of male field cricket, Gryllus bimaculatus, agonistic displays. The displays were quantified under three social environments which varied in the potential benefits of fighting: males with other males only, males with other males and female scents, and males with other males and females. We found that (1) the presence of females elicited an increase in agonistic displays characteristic of intermediate levels of escalation, (2) female scents did not produce a similar increase in the frequency of agonistic displays, and (3) in the presence of females, the frequency of agonistic displays was positively correlated with mating success. Aggressive stridulation, an energetically low-cost display, was more strongly associated with mating success than were more costly displays. The results are discussed in the context of the evolutionary theory of aggression and in the context of cricket mating systems.     

No Effect of Body Size on the Frequency of Calling and Courtship Song in the Two-Spotted Cricket,Gryllus bimaculatus

The relationship between body size and vocalization parameters has been studied in many animal species. In insect species, however, the effect of body size on song frequency has remained unclear. Here we analyzed the effect of body size on the frequency spectra of mating songs produced by the two-spotted cricket, Gryllus bimaculatus. We recorded the calling songs and courtship songs of male crickets of different body sizes. The calling songs contained a frequency component that peaked at 5.7 kHz. On the other hand, courtship songs contained two frequency components that peaked at 5.8 and 14.7 kHz. The dominant frequency of each component in both the calling and courtship songs was constant regardless of body size. The size of the harp and mirror regions in the cricket forewings, which are the acoustic sources of the songs, correlated positively with body size. These findings suggest that the frequency contents of both the calling and courtship songs of the cricket are unaffected by whole body, harp, or mirror size.     

Seasonal Variation in Female Response to Male Calling Song in the Field Cricket, Gryllus rubens

Conspicuous traits that make males attractive to females may make them vulnerable to predators. Females that approach conspicuous males may increase their risk of predation. This means that selection for reduced male conspicuousness in the presence of predators may be due to sexual selection resulting from altered female behavior in the face of increased predator risk. We examine this hypothesis in the field cricket, Gryllus rubens, in which male calling song attracts both conspecific females for mating and parasitoid flies (Ormia ochracea) which kill their hosts within a week. Female crickets are also parasitized by these flies as a result of associating with calling males. In northern Florida crickets that emerge in the spring are not subject to fly parasitism whereas autumn crickets encounter large numbers of flies. We predicted that autumn females should be less attracted to male song than spring females. We tested female response to male calls in a rectangular arena in which male calling song was broadcast from a speaker. Spring females readily approached the speaker but autumn females were less likely to approach and remain in the vicinity of the speaker. These results emphasize the importance of considering how risk affects the evolution of conspicuous male behavior both directly through its effect on the male and indirectly through its effect on female responses to males.     

Temporal Shifts in Conspicuousness: Mate Attraction Displays of the Texas Field Cricket, Gryllus texensis

Conspicuous mate attraction displays can simultaneously draw the attention of potential mates and predators, placing the signaller in peril of becoming prey. The balance between these countervailing forms of selection has the potential to shape mate attraction displays. Male Texas field crickets (Gryllus texensis; Orthoptera) signal acoustically to attract mates. Mating signals also attract acoustically orienting parasitoid flies (Ormia ochracea; Tachinidae). Both the abundance of female crickets and parasitoid flies fluctuates throughout the night. We show mate attraction displays exhibit diel shifts that correlate positively with expected female cricket presence and negatively with expected parasitoid fly activity. During early evening, when parasitoids are most common and mating is scarce, crickets signal less often and with reduced conspicuousness. During the second half of the evening, when sexually receptive females are abundant and parasitoids are scarce, crickets signal more often and with enhanced conspicuousness. These diel shifts in mate attraction displays do not appear to result from male crickets detecting parasitoid flies or female crickets and altering their behaviour accordingly. Males in close proximity to parasitoid flies or female crickets do not signal differently than lone males. Instead, diel pattern shifts in mate attraction displays appear to be a selective response to trade‐offs between natural selection via parasitism and sexual selection via mate choice.     

Jhe in Gryllus assimilis: cloning, sequence-activity associations and phylogeny

The 458 amino acid sequence of a mature JHE protein from the cricket Gryllus assimilis was identified after isolating the partial cDNA sequence encoding this protein from a fat body and midgut cDNA library. This hemimetabolan JHE sequence shows over 40% amino acid similarity to the known JHE sequences of several holometabolous insects. It also includes previously determined peptide sequences for G. assimilis JHE as well as two other motifs associated with JHE enzymes in holometabolous insects. The predicted molecular weight of the protein agrees with that of the JHE previously purified from G. assimilis. Partial genomic sequence encoding the Jhe contains two large (1330 and 2918 bp) introns. No coding DNA sequence variation was observed over a 1293 bp region between selected lines differing six to eight-fold in hemolymph JHE activity. However, a 19 bp indel was found in one of the introns; the insertion was strongly associated with elevated hemolymph activity, both in the selected lines and in the F₂ progeny of crosses between them. Phylogenetic analyses localised the G. assimilis JHE to a clade containing dipteran and coleopteran JHEs, with lepidopteran JHEs occurring in a separate clade.     

Selective phonotaxis to high sound-pulse rate in the cricket Gryllus assimilis

Calling song of the cricket Gryllus assimilis is unusual among Gryllus spp. in the high sound-pulse rate, ca. 80 Hz, within its chirps. We asked whether, as in other cricket species, females were able to analyze such a high pulse rate. In phonotaxis experiments, females failed to respond to stimuli with pulse rates substantially higher or lower than the species-typical value, demonstrating that they are indeed selective for this parameter. We also examined how pulse rate was represented by modulation in firing rate of the neuron AN1, the main carrier of information about cricket-song-like stimuli to the brain. For attractive stimuli, i.e. with high pulse rates, modulation of AN1 firing rate through time was surprisingly modest. This suggests that the brain circuits that analyze AN1 spike trains might be more sensitive to slight variations in AN1 firing rate than their counterparts in more slowly singing species.     

Reproductive Success and Body Size in the Cricket Gryllus firmus

Male body size influences mate choice and sexual selection in many animal species. Here we investigate the role of male body size in the reproductive success of the field cricket Gryllus firmus. This species hybridizes with a close smaller relative, G. pennsylvanicus, and it is thought that this size difference may affect reproductive isolation between these species. We paired large and small G. firmus males with a single G. firmus female and genotyped the resulting offspring. Overall, larger males sired a greater proportion of offspring and in a majority of the crosses the larger male sired all of the offspring. For crosses in which both males sired offspring, there was no difference in the proportion of offspring sired by small and large males. Intrasexual competition, female choice, and differences in ejaculates between males could all influence the patterns we observe. We discuss the implications of our findings within the context of reproductive isolation between G. firmus and G. pennsylvanicus.     

Wing-flick Signals in the Courtship of the African Cave Cricket,Phaeophilacris spectrum

The male of the African cave cricket Phaeophilacris spectrum (Saltatoria: Grylloidea: Phalangopsidae) possesses tegmina without stridulatory organs, and both females and males lack tympanal organs. Therefore acoustic communication in the usual sense, which is typical for most crickets, is absent in this species. However, adaptations of the wing articulation allow the males to flick their wings forward over their heads. During courtship these movements are performed in series of 4–5 wing-flicks at a rate of 8–12 Hz (called wing-flick series = WFS) which elicit low-frequency air movements. Such signals may have taken over the functional significance of an acoustic ‘courtship song’. A quantitative analysis of the cricket's behaviour showed that in terms of frequency and total duration, ‘wing-flick series’ and ‘rocking’ behaviour are the most prominent signals of the male's courtship display. Moreover, analysis of the spatial relationships between male and female demonstrates that the wing-flicking is directed towards the female. The response of a female to a wing-flicking, courting male seems mainly to be calmed down and to reach a passive, receptive state, necessary for subsequent copulation. Females confronted with a male's courtship display exhibited a significantly higher threshold to disturbing stimuli than uncourted ones.     

Previous Motor Experience Enhances Courtship Behavior in Male Cricket <Emphasis Type=Italic>Gryllus bimaculatus</Emphasis>

In crickets Gryllus bimaculatus, flight has been shown to be able to promote aggressive encounters between males and to suppress escape behavior. The aim of this study was to examine the influence of flight on male behavior in male–female interactions. We found that flown males demonstrate enhanced courtship behavior. The latency of calling song was significantly shorter, while the relative total duration of singing as well as the duration of singing episodes longer in flown males than in the control. Mating rate was also significantly higher in the experimental group containing flown males. The results suggest that, in addition to previously reported effects on aggressiveness and escape, flying has a profound accelerating effect on male courtship behavior.     

Eicosanoids mediate nodulation reactions to bacterial infections in adults of the cricket,Gryllus assimilis

Nodulation is the temporally and quantitatively most important cellular defense reaction to bacterial infections in insects. Inhibition of eicosanoid biosynthesis in adults of the cricket, Gryllus assimilis, immediately prior to intrahemocoelic injections of the bacterium, Serratia marcescens, sharply reduced the nodulation response. Separate treatments with specific inhibitors of phospholipase A(2), cyclooxygenase, and lipoxygenase reduced nodulation, supporting our view that nodule formation is a complex process involving lipoxygenase and cyclooxygenase products. The inhibitory influence of dexamethasone was apparent within 2h of injection, and nodulation was significantly reduced, relative to control crickets, over 22h. The dexamethasone effects were reversed by treating bacteria-injected insects with the eicosanoid-precursor polyunsaturated fatty acid, arachidonic acid. Low levels of arachidonic acid were detected in fat body phospholipids, and fat body preparations were shown to be competent to biosynthesize eicosanoids from exogenous radioactive arachidonic acid. These findings in a hemimetabolous insect broaden our hypothesis that eicosanoids mediate cellular immune reactions to bacterial infections in most, if not all, insects.     

Multilaminar/ Vesicular Bodies Accumulating Glycoconjugates in Primary Spermatocytes of Cricket, Gryllus bimaculatus

Lectin cytochemistry was carried out on thin sections of 6th-instar cricket testis using two GalNAc-specific lectins, Dolichos biflorus agglutinin (DBA) and Helix pomatia agglutinin (HPA), and the binding sites in primary spermatocytes were surveyed. Gold particles showing DBA-binding are observed specifically in dense-body clusters. These bodies are about 100-300 nm in diameter and exhibit multilaminar or multivesicular structure. HPA can bind to the dense-body clusters and another kind of larger multivesicular structures. These bodies seem to contain some heterogeneous substances, and sometimes show an autophagosome-like structure. The ultrastructures of these organelles surveyed in conventional Epon sections confirmed the structures of these multilaminar/vesicular bodies in cricket spermatocytes, which may play certain roles in intracellular circulation and degradation of glycoconjugates.     

Early embryonic development of the head region of Gryllus assimilis Fabricius, 1775 (Orthoptera,Insecta)

We report our investigations on the embryonic development of Gryllus assimilis, with particular attention to the head. Significant findings revealed with scanning electron microscopy (SEM) images include: (1) the pre-antennal lobes represent the anterior-most segment that does not bear any appendages; (2) each of the lobes consists of central and marginal regions; (3) the central region thereof develops into the protocerebrum and the optic lobes, whereas the marginal region thereof becomes the anterior portion of the head capsule; (4) the initial position of the antennal segment is posterior to the mouth region; (5) appendage anlagen are transitorily present in the intercalary segment, and they later vanish together with the segment itself; (6) a bulged sternum appears to develop from the ventral surface of the mandibular, maxillary and labial segments. Embryonic features are then compared across the Insecta and further extended to the embryos of a spider (Araneae, Chelicerata). Striking similarities shared by the anterior-most region of the insect and spider embryos lead the authors to conclude that such comparison should be further undertaken to cover the entire Euarthropoda. This will help us to understand the embryology and evolution of the arthropod head.     

Reproductive Isolation in the Wood Cricket Gryllus vernalis (Orthoptera: Gryllidae)

Two species of closely related wood crickets, Gryllus vernalis (Orthoptera: Gryllidae) and G. fultoni, occur together in the eastern USA and have a similar calling‐song structure, consisting of three‐pulse chirps. Previous studies revealed that male calling song and female selectivity were divergent between sympatric and far allopatric populations of G. fultoni, consistent with the pattern expected of reproductive character displacement. We studied the reproductive isolation of G. vernalis in relation to G. fultoni by investigating the geographic variation in calling songs of G. vernalis and by examining close‐range mating behaviors. Neither field nor laboratory studies revealed differences in any of the calling‐song characters between sympatric and allopatric populations, but this could reflect the limited sampling within the relatively small region of allopatry for G. vernalis. Although close‐range mating trials revealed that females of both species discriminated against heterospecific mating partners, the strength of discrimination was especially strong in females of sympatric G. vernalis populations. Our studies of long‐range and close‐range mating behaviors suggest that selection pressures for reproductive isolation are exerted primarily on close‐range mating behaviors in G. vernalis but on long‐range mating behaviors in G. fultoni.     

On Some Peculiarities of Mechanisms of Phonotaxis Selectivity in the Cricket Gryllus bimaculatus

It is shown that positive phonotaxis of female crickets Gryllus bimaculatus is characterized by a band-pass tuning to the pulse repetition period (PRP) in the male communicative calling song; this feature can be provided by two neuronal mechanisms—high-frequency (HFF) and low-frequency (LFF) filters. With elevation of temperature, PRP becomes shorter. The tuning of phonotaxis to this parameter changes correspondingly. It is suggested that this coupling is provided by differences in properties of LFF and HFF with respect to the environmental temperature as well as to the sound pressure level (SPL) of the signal. In behavioral experiments on a Y-maze labyrinth, the tuning of the female phonotaxis selectivity to PRP in a model calling song was determined for 20 and 25°C at 70 dB SPL and for SPL changing from 70 to 85 dB at 20°C. At an increase both of temperature and of SPL, the optimum of the phonotaxis tuning shifted towards the lower values of PRP. The agreement of the results of this study with the above-exposed hypothesis indicates in favor of possible existence in the cricket of neuronal mechanisms that are different in their characteristics with respect to temperature and signal intensity.