Academic literature on the topic 'Jack jumper ants'

We caught solitary foragers of the Australian Jack Jumper ant, Myrmecia croslandi , and released them in three compass directions at distances of 10 and 15 m from the nest at locations they have never been before. We recorded the head orientation and the movements of ants within a radius of 20 cm from the release point and, in some cases, tracked their subsequent paths with a differential GPS. We find that upon surfacing from their transport vials onto a release platform, most ants move into the home direction after looking around briefly. The ants use a systematic scanning procedure, consisting of saccadic head and body rotations that sweep gaze across the scene with an average angular velocity of 90° s −1 and intermittent changes in turning direction. By mapping the ants’ gaze directions onto the local panorama, we find that neither the ants’ gaze nor their decisions to change turning direction are clearly associated with salient or significant features in the scene. Instead, the ants look most frequently in the home direction and start walking fast when doing so. Displaced ants can thus identify home direction with little translation, but exclusively through rotational scanning. We discuss the navigational information content of the ants’ habitat and how the insects’ behaviour informs us about how they may acquire and retrieve that information.

Background: Myrmecia pilosula (the jack jumper ant, JJA) is the principal cause of ant venom anaphylaxis in Australia. Whereas honeybee and wasp venom allergy can be treated by venom immunotherapy (VIT), no such treatment is available for ant sting allergy. In addition, information on the natural history of JJA sting allergy is required to identify those most likely to benefit from immunotherapy. The main objectives of this research were to establish: (i) the prevalence, natural history and determinants of reaction severity for JJA allergy, and; (ii) the efficacy and tolerability of JJA VIT. Methods: A search of the Royal Hobart Hospital (RHH) forensic register, a random telephone survey, and a review of emergency department (ED) presentations were performed. Three hundred eighty-eight JJA allergic volunteers were assessed, including serum venom-specific IgE RAST, and then followed up for accidental stings over a 4-year period. Finally, a randomised double-blind, placebo-controlled, crossover trial of JJA VIT was performed. Laboratory parameters measured during the trial were; leukocyte stimulation index (SI), IL-4 production, IgE RAST, histamine release test (HRT), leukotriene release test (LRT) and basophil activation test (BAT). Intradermal venom skin testing (VST) was also performed at trial entry. Findings: The prevalence of JJA sting allergy was 2.7% in the Tasmanian population, compared to 1.4% for honeybee. People aged 35 or older had a greater risk of both sting allergy and hypotensive reactions. Four deaths were identified, all in adults with significant comorbidities. During follow-up, 79 (70%) of 113 accidental jack jumper stings caused systemic reactions. Only prior worst reaction severity predicted the severity of follow-up reactions, with the majority of people experiencing similar or less severe reactions when stung again. Sixty-eight otherwise healthy JJA allergic adult volunteers were enrolled in the clinical trial. Systemic reactions to therapy were recorded in 34% during VIT. Objectively defined systemic reactions to sting challenges arose in 1/35 after VIT (mild self-limiting urticaria only) versus 21/29 in the placebo group. Treatment with oxygen, intravenous adrenaline infusion and volume resuscitation was effective and well tolerated. Hypotension was always accompanied by a relative bradycardia, which was severe and treated with atropine in two patients. In the placebo group, only VST and HRT were predictive of sting challenge results. Although IgE RAST, leukocyte SI and IL-4 production, LRT and BAT all correlated well with VST, they did not predict sting challenge outcome. After successful VIT, venom-induced leukocyte IL-4 production tended to fall, whereas IgE RAST increased and a natural decline in HRT reactivity was reversed. Interpretation: VIT is highly effective in prevention of JJA sting anaphylaxis and is likely to be of most benefit to people with a history of severe systemic reactions, which usually occur in people aged over 35. Neurocardiogenic mechanisms &/or direct cardiac effects may be important factors in some anaphylaxis deaths. Systemic reactions to immunotherapy are common and require immediate access to resuscitation facilities. The HRT warrants further investigation as a test for selecting those most likely to benefit from VIT. None of the tests evaluated appear to be reliable markers of successful VIT.

A solitary foraging ant needs to rely exclusively on her navigational skill set to successfully navigate to and from goals such as the nest and food sites. Of interest is how ants are able to acquire this navigational information at a young age, before they become experienced workers and how this eventually shapes them into becoming efficient foragers. Ants of Myrmecia croslandi are highly visual, solitary foragers that exhibit no evidence of chemical trail following or recruitment. Therefore, a forager leaving the nest for the first time, must do so completely on her own, first by deciding where to go and second by utilising the information she has acquired from the environment to journey between sites. By identifying and individually following ants, I demonstrate that ants exhibit highly individual behaviour in most tasks, from early learning, and daily foraging to navigating from unfamiliar locations. First, I document the spatial and temporal variation in individual foraging behaviour at two nests of M. croslandi over a two-year period. Ants can take variable routes to the same food site and travel the longest distance when they forage on trees. Individual ants depart the nest at different times and a few ants perform multiple trips per day. Surprisingly, not a single ant foraged on consecutive days. By examining the behaviour of inexperienced ants at the nest, I provide a detailed analysis of the learning walks of M. croslandi. Most learning walks take place in the morning with a narrow time window separating the first two learning walks. There are no common bearing or gaze directions between ants, however, (a) in subsequent walks ants always explore directions that they have not previously visited and (b) ants engage in a systematic, saccadic scanning behaviour. I also discuss the significant differences between learning walks of M. croslandi and those previously studied in two other ant species, especially in relation the ‘turn back and look’ behaviour. In displacement experiments, I provide supporting evidence of a quick scanning behaviour that occurs as soon as ants are released. I examine the effect of a conflict in navigational information on successful homing by comparing full and zero vector ants. Zero vector ants are significantly better at navigating home, especially when released at unfamiliar sites. With the aid of the extensive individual foraging histories available to me, I show how in most cases, scene familiarity plays a role in driving ants home from unfamiliar displacement locations and discuss in detail behaviours that are exceptions to this. Finally, I provide the first evidence of the use of artificial landmarks near the nest in this species, which increases the accuracy with which ants pinpoint the nest entrance, even though they do not appear to make use of such landmarks in the wild and discuss my findings in relation to other ants. I also document the occurrence of re-orientation walks in response to an altered visual environment which show that ants are more directed as a result of re-learning.