Developmental periods of Oenopia conglobata contaminata (Col.: Coccinellidae) reared on eggs of Sitotroga cerealella (Lep.: Gelechiidae) and Ephestia kuehniella (Lep.: Pyralidae) at constant temperatures

The coccinellid Oenopia conglobata contaminata (Menteries) is one of the most important predators of orchard pests in Iran. The effect of eggs of Sitotroga cereallela Olivier (Lep.: Gelechiidae) and Ephestia kuehniella Zeller (Lep.: Pyralidae) on development and survival of this beetle was studied and compared under laboratory conditions (five constant temperatures i.e., 22.5 ± 1, 25 ± 1, 27.5 ± 1, 30 ± 1 and 32.5 ± 1 °C 55 ± 5% relative humidity (R. H.) and a 16:8 h light: dark photoperiod). Total developmental time at the above-mentioned temperatures were 28.83 ± 0.17, 24.52 ± 0.37, 21,39 ± 0.21 17.92 ± 0.16 and 18.22 ± 0.29 days on S. cereallelaand27 ± 0.38, 23.32 ± 0.14, 19.57 ± 0.28, 16.14 ± 0.17 and 16.33 ± 0.05 days on E. kuehniella. The lower developmental thresholds (T0) of egg, larva, pupa and egg to adult on E. kuehniella were estimated15.02, 8.6, 7.48 and 8.55 ºC and the thermal constant for these periods calculated as 38.16, 222.22, 71.9 and 370.37 DD. The lower developmental thresholds on S. cereallela were found to be 13.79, 5.6, 5.82 and 6.54 ºC andthermal constant for the mentioned periods were 41.15, 277.77, 91.7, 454.54 DD, respectively. Although significant differences between developmental times at different temperatures exist, no significant differences was observed between 30 and 32.5 °C for two prey species. The results suggest that E. kuehniella serves as a more effective host than S. cereallela for rearing of coccinellid O. conglobata

Mechanism Design on Trust Networks

Abstract. We introduce the concept of a trust network—a decentralized payment infrastructure in which payments are routed as IOUs between trusted entities. The trust network has directed links between pairs of agents, with capacities that are related to the credit an agent is willing to extend another; payments may be routed between any two agents that are connected by a path in the network. The network structure introduces group budget constraints on the payments from a subset of agents to another on the trust network: this generalizes the notion of individually budget constrained bidders. We consider a multi-unit auction of identical items among bidders with unit demand, when the auctioneer and bidders are all nodes on a trust network. We define a generalized notion of social welfare for such budgetconstrained bidders, and show that the winner determination problem under this notion of social welfare is NP-hard; however the flow structure in a trust network can be exploited to approximate the solution with a factor of 1 − 1/e. We then present a pricing scheme that leads to an incentive compatible, individually rational mechanism with feasible payments that respect the trust network’s payment constraints and that maximizes the modified social welfare to within a factor 1 − 1/e.

The role of compatibility in the diffusion of technologies through social networks

In many settings, competing technologies -- for example, operating systems, instant messenger systems, or document formats -- can be seen adopting a limited amount of compatibility with one another; in other words, the difficulty in using multiple technologies is balanced somewhere between the two extremes of impossibility and effortless interoperability. There are a range of reasons why this phenomenon occurs, many of which -- based on legal, social, or business considerations -- seem to defy concise mathematical models. Despite this, we show that the advantages of limited compatibility can arise in a very simple model of diffusion in social networks, thus offering a basic explanation for this phenomenon in purely strategic terms. Our approach builds on work on the diffusion of innovations in the economics literature, which seeks to model how a new technology A might spread through a social network of individuals who are currently users of technology B. We consider several ways of capturing the compatibility of A and B, focusing primarily on a model in which users can choose to adopt A, adopt B, or -- at an extra cost -- adopt both A and B. We characterize how the ability of A to spread depends on both its quality relative to B, and also this additional cost of adopting both, and find some surprising non-monotonicity properties in the dependence on these parameters: in some cases, for one technology to survive the introduction of another, the cost of adopting both technologies must be balanced within a narrow, intermediate range. We also extend the framework to the case of multiple technologies, where we find that a simple model captures the phenomenon of two firms adopting a limited "strategic alliance" to defend against a new, third technology