Although sublethal dosages of insecticide to nontarget insects have never been an important issue, they are attracting more and more attention lately

The residue of imidacloprid in the nectar and pollens of the plants is toxic not only to adult honeybees but also the larvae. Our understanding of the risk of imidacloprid to larvae of the honeybees is still in a very early stage. In this study, the capped-brood, pupation and eclosion rates of the honeybee larvae were recorded after treating them directly in the hive with different dosages of imidacloprid. The brood-capped rates of the larvae decreased significantly when the dosages increased from 24 to 8000 ng/larva. However, there were no significant effects of DMSO or 0.4 ng of imidacloprid per larva on the brood-capped, pupation and eclosion rates. Although the sublethal dosage of imidacloprid had no effect on the eclosion rate, we found that the olfactory associative behavior of the adult bees was impaired if they had been treated with 0.04 ng/larva imidacloprid in the larval stage. These results demonstrate that a sublethal dosage of imidacloprid given to the larvae affects the subsequent associative ability of the adult honeybee workers. Thus, a low dose of imidacloprid may affect the survival condition of the entire colony, even though the larvae survive to adulthood.

The dramatic loss of honey bees is a major concern worldwide. Previous studies have indicated that neonicotinoid insecticides cause behavioural abnormalities and have proven that exposure to sublethal doses of imidacloprid during the larval stage decreases the olfactory learning ability of adults. The present study shows the effect of sublethal doses of imidacloprid on the neural development of the honey bee brain by immunolabelling synaptic units in the calyces of mushroom bodies. We found that the density of the synaptic units in the region of the calyces, which are responsible for olfactory and visual functions, decreased after being exposed to a sublethal dose of imidacloprid. This not only links a decrease in olfactory learning ability to abnormal neural connectivity but also provides evidence that imidacloprid damages the development of the nervous system in regions responsible for both olfaction and vision during the larval stage of the honey bee.

This paper presents a 9.4/18.8-GHz harmonic radar to investigate the behavior of bees with colony collapse disorder. The challenges of using harmonic radar for bee searching include the requirements of high range accuracy and high sensitivity. A new harmonic radar using the pseudorandom code positioning technique to simultaneously achieve high range accuracy and high sensitivity is proposed. This study also proposes a new method to cancel the local leakage to further improve sensitivity. To realize the transponder, a compact antenna is designed using the topology characteristics of the composite right/left-handed transmission-line concept. The measured sensitivity of the transceiver is -120 dBm, which is 27 dB lower than the noise level. Field testing results demonstrate a 60-m detection range within 1-m distance error with 1.75-W transmitting power. The significant improvement of the sensitivity and the range accuracy reveal the advantages of applying the code-positioning technique to the harmonic radar.