Field effects of faecal residues from ivermectin slow-release boluses on the attractiveness of cattle dung to dung beetles.

A 2-year study was performed in two sites in southern France to assess the effect of ivermectin residues on the attractiveness of cattle dung to colonizing insects. Insect captures were compared between pitfall traps baited with dung from untreated cattle and dung from cattle that had been treated with a slow-release (SR) bolus of ivermectin. Cattle dung was collected at different times after treatment (4, 14, 42, 70 and 98 days). Excretion showed a plateau, with levels ranging between 0.688 µg and 1.123 µg ivermectin per gram of wet dung. Faecal residues affected insect captures at both sites. Effects were independent of the time dung was collected after treatment, except for one result subsequent to a severe drought during the baiting period. Ivermectin-contaminated dung showed a significant attractive effect, with increased captures regardless of the guild to which beetles belonged. This study demonstrates the attractiveness of ivermectin residues over a long period after the treatment of animals. It draws attention to the danger of widespread use of this endectocide-based SR bolus, which is attributable to the preferential attraction of insects to treated dung, which potentially puts at risk the survival of their offspring.

Temporal coexistence of dung-dweller and soil-digger dung beetles (Coleoptera, Scarabaeoidea) in contrasting Mediterranean habitats.

The western part of the Mediterranean basin is a transitional biogeographical region for the distribution of the representatives of the main guilds of dung beetles; towards the south, Aphodiinae (dung-dwellers) become scarce, whereas northwards Scarabaeinae (soil-diggers) progressively disappear. The number of species in local dung beetle assemblages is enhanced by this double faunistic contribution. Annual dung beetle assemblages were sampled in two sub-Mediterranean sites, which differed by 600 m in elevation, in order to determine the phenological dynamics related to the way of using dung (dung-dwellers/Aphodiinae vs. soil-diggers/Scarabaeinae and Geotrupinae). Aphodiids were active all year round, although they were affected by summer drought and, at high elevation, by the length of the cold season. This reduced activity was related to an impoverishment of Aphodiinae and to reduced temporal segregation between species. In contrast, soil-diggers were not active all year round and showed different species assemblages in the two sites. An extension of the activity period of these beetles was observed due to the occurrence of cold resistant species at high elevation. Our results suggested that the occurrence of soil-diggers seemingly did not affect the seasonality of dung-dwellers; their local abundance showed no negative correlation and, most importantly, phenological differences between dung-dwellers were always significantly higher than the seasonal differences between dwellers and diggers.

Environmental risk assessment of veterinary pharmaceuticals: development of a standard laboratory test with the dung beetle Aphodius constans.

The environmental risk assessment of veterinary pharmaceuticals for dung beetles is required if the substance is an anti-parasiticide for the treatment of pasture animals. However, the demonstration of the environmental safety of those substances for dung fauna is hampered by the fact that no standardized laboratory test system is currently available. Here a test system using the temperate dung beetle species Aphodius (Agrilinus) constans (Scarabaeidae: Aphodiinae) Duftschmidt is described. The survival of first instar larvae of A. constans exposed to a model substance, dimethoate, spiked into formulated (i.e. dried, formulated and re-wetted) or fresh dung was measured over a period of three weeks. Larvae performed better in formulated dung which also proved to be more suitable for mixing-in test substances homogenously. Dimethoate caused significant larval mortality with LC50 values within a range of 1.3-2.8 mg a.s./kg dung (d.w.), depending on the dung type. Based on the data presented here, it is recommended to incorporate this new test system in the risk assessment process for veterinary pharmaceuticals. However, an international ringtest should to be performed beforehand to ensure adequate validation of the method.

Taxonomy of Iberian Hoplia (Col., Scarabaeoidea, Hopliinae) based on mtDNA analysis.

The morphology of some Hoplia species (Scarabaeoidea: Hopliinae) is so variable that parapatric populations have often been considered different species or subspecies. In this study we analyze the nucleotide sequences of a fragment of mitochondrial gene cytochrome c oxidase subunit I (COI) of six species and two subspecies of Palaearctic Hoplia to reexamine the species limits. Based on the analysis of sequences from COI and morphological and ecological observations, we consider Hoplia freyi Baraud to be a junior synonym of Hoplia chlorophana Erichson and H. philanthus ramburi Heyden to be a junior synonym of H. philanthus philanthus (Fuessly). However, complete resolution of relationships among H. philanthus subspecies requires the addition of sequences from genes evolving faster than COI. Phylogenetic relationships among the species studied are discussed.

Suspected side effects of a herbicide on dung beetle populations (Coleoptera: Scarabaeidae).

This paper addresses the association between use of a herbicide and anecdotal reports of reduced dung degradation and dung beetle populations. Dung beetles were monthly collected at two adjacent ranches in Mexico. Ranches were similar in area, elevation, exposition, soil, and vegetation, but differed in weed control. Ranch A controlled weeds manually, and ranch B controlled unwanted vegetation with applications of the herbicide Tordon 101M. The main species recovered on each ranch (Ataenius apicalis) was significantly more abundant at ranch A than at ranch B. Conversely, similar numbers of a second species, Ataenius sculptor, were recovered from both ranches. Three lines of evidence support the tentative conclusion that herbicide applications may be causing a decline in populations of A. apicalis on ranch B. First, the greatest reductions of A. apicalis were observed during periods of herbicide application. Second, A. sculptor, apparently little affected by these same herbicide applications, is active primarily during months without herbicide applications. Third, preliminary results of laboratory studies show that exposure to herbicide can impair reproductive function of the dung beetle Canthon cyanellus.

The negative effects of the residues of ivermectin in cattle dung using a sustained-release bolus on Aphodius constans (Duft.) (Coleoptera: Aphodiidae).

This paper reports the findings of two trials into the effects of the treatment of cattle with ivermectin slow-release (SR) bolus on the larval development of the dung beetle Aphodius constans Duft. Rectal faecal samples were collected prior to treatment and every 3 and 2 weeks in a first and second trial, respectively, and up to 156 days post-administration of the SR bolus. Faecal ivermectin concentration reached a peak at 63 days post-treatment (1427 ng g(-1)) and ivermectin was detected up to 147 days post-treatment in the first trial (7.2 ng g(-1)). First stage larvae of A. constans were reared with control or contaminated dung and adult beetles were counted after emergence. In the first trial, the comparison of pairwise samples showed that ivermectin prevented the development of larval A. constans until day 105, while at day 135 the rate of emergence was still significantly lower than the corresponding series of control (p < 0.05). In the second trial, the difference between control and treated series remained significant until 143 days post-treatment, with no emergence until 128 days post-administration of SR bolus to cattle. These results show the negative effect of ivermectin on the development of larval A. constans, even at a low concentration (38.4 ng g(-1)). The administration of ivermectin sustained-release bolus to cattle was highly effective in killing dung beetle larvae for approximately 143 days after treatment. The results were similar when dung was obtained from a single animal kept alone, or from a blending of faecal pats obtained from a group of animals kept in field conditions during the whole trial period.