Larval development and voracity of Eupeodes americanus (Diptera: Syrphidae): comparison of the focal prey Aphis gossypi (Hemiptera: Aphididae) and the banker prey Rhopalosiphum padi (Hemiptera: Aphididae)

Unlike European species,the potential of Nearctic syrphids as biological control agents is still poorly studied.However,the American hoverfly,Eupeodes americanus(Wiedemann),has recently demonstrated promising traits as a biocontrol agent,notably against the foxglove aphid,Aulacorthum solani Kaltenbach,on pepper.The present study aims to extend our knowledge of the American hoverfly by evaluating its potential as a biocontrol agent in a banker plant system against the melon aphid,Aphis gossypi Glover,in a greenhouse cucumber crop.The preimaginal development and voracity of E.americanus were compared when preying upon the focal prey/pest(A.gossypi)or the banker prey(bird cherry-oat aphid,Rhopalosiphum padi L.)by daily observations of larvae from egg to adult.Preimaginal development time,survival rate,and occurrence of deformation were similar on both prey species.The weight of third instar and pupae,however,was higher for larvae that fed on the banker prey.The ad libitum voracity of the syrphid larvae was generally very high and did not significantly differ between prey species,except for the third-instar larvae which consumed more focal prey.Results suggest that a banker plant system involving the bird cherry-oat aphid may be a promising tactic for utilizing E.americanus for melon aphid biocontrol.

独眼巨人

这12栋房子作为Hilversum的林中高档住宅区域和从Diependaal来的二级公路防噪音路堤融为一体。虽然基地环境不那么优越，甲方在一开始也抱有怀疑态度，此设计带有未来感而非幻想感的设计还是吸引了住户。他们在看到设计图纸后就当即买下。而建成则是几年之后的事情了。

Gregarious pupation act as a defensive mechanism against cannibalism and intraguild predation

Coccinellid pupae use an array of defensive strategies against their natural enemies. This study aims to assess the efficiency of gregarious pupation as a defensive mechanism against intraguild predators and cannibals in coccinellid. The study was designed specifically （i） to determine the natural occurrence of gregarious pupation in the field for different coccinellid species, and （ii） to evaluate the adaptive value of gregarious pupation as a defensive mechanism against 2 types of predators （i.e., cannibals and intraguild predators）. In the field, gregarious pupation consisted of a group of 2-5 pupae. The proportion of gregarious pupation observed varied according to species, the highest rate being observed with Harmonia axyridis Pallas （Coccinellidae; 14.17%）. Gregarious pupation had no impact on the probability that intraguild predators and cannibals locate pupae. Intraguild predation occurred more often in site with gregarious pupation, while cannibalism occurred as often in site with gregarious pupation as in site with isolated pupa. However, for a specific pupa, the mortality rate was higher for isolated pupae than for pupae located in a gregarious pupation site both in the presence of intraguild predators and in the presence of cannibals. The spatial location of pupae within the group had no impact on mortality rate. Since it reduces the risk of predation, it is proposed that gregarious pupation act as a defensive mechanism for 11. axyridis pupae.

Oviposition behavior of the mirid Macrolophus pygmaeus under risk of intraguild predation and cannibalism

Zoophytophagous mirid species,that feed and develop either on prey or plant resources,are often found simultaneously on the same host.Hence,these species can engage in both intraguild predation and cannibalism,which can pose a threat to mirid eggs.Ovipositing females may respond to such risks of predation on their eggs by reducing the number of eggs laid or selecting safer oviposition sites.We tested the oviposition behavior of Macrolophus pygmaeus(Rambur)(Hemiptera:Miridae)females under the risk of cannibalism by M.pygmaeus males and intraguild predation by Nesidiocoris tenuis(Reuter)males(Hemiptera:Miridae)under laboratory conditions.Intraguild predators and cannibals were introduced during or after the oviposition period.The number of eggs laid(using counts of newly hatched nymphs)and their proportion on each part of a tomato plant were both measured.The results reveal that only cannibalism by M.pygmaeus males after the period of oviposition significantly decreased the number of hatched eggs.Cannibalism thus represents a greater risk to mirid eggs than intraguild predation.The M.pygmaeus female responded to the presence of potential intraguild predators(or competitors)by decreasing the nu mber of eggs laid in the upper leaves.The results suggest that M.pygmaeus females avoid competition by N.tenuis,by laying fewer eggs on upper leaves.Cannibalism could regulate zoophytophagous predator populations under prey scarcity conditions and minimize the risk of crop damage associated with those biological control agents.

5 Wonders of Mexico

说起墨西哥，人们自然会联想到高耸的玛雅金字塔、延绵的山峦、热情的椰林沙滩、辛辣的美食和奔放的音乐。下面我们就一起去墨西哥转转吧。