Question

Soybean aphids and their parasitoids are part of a rather complex drama that is playing out in miniature in the soybean fields you see any time you leave Champaign-Urbana (see panel a) above). Two different wasps (a braconid wasp and an aphelinid wasp) parasitize aphids. These two aphid parasitoids are themselves parasitized as larvae inside the aphid by a cynipid wasp (we call the cynipid wasp a hyperparasitoid, meaning it is a parasitoid of another parasitoid - it lays its eggs inside a parasitized aphid, and upon hatching its larvae consume the other parasitoid larvae - not the aphid). The cynipid wasp is itself parasitized by a second hyperparasitoid (a megaspilid wasp) whose larvae consume the pupal stage of the cynipid wasp inside the mummified aphid case.

Panel b) shows data on aphid population size from a 10-year study on the effectiveness of using parasitoid wasps as a biocontrol agent of aphids. (Data from every second year shown. Note that aphids overwinter as eggs and their populations on soybeans rapidly increase each year once soybean plants emerge.).

Data from year 1 shows a soybean plot covered in insect netting to prevent any parasitoids reaching the aphids.

Data from year 3 shows the same soybean plot, but this time braconid wasps were introduced into the net-covered plot. Despite resulting in pronounced population cycles, the braconid wasp was able to drastically reduce aphid population size.

In years 5-9 the insect netting was removed to test the effectiveness of braconid wasps in open air field conditions. Braconid wasps were again released in the field at the beginning of the summer season. However, in years 5-7, the effectiveness of the braconid wasp in controlling the aphid population was much reduced.

Despite no change in treatment in year 9, the effectiveness of braconid wasp biocontrol on aphids again improved.

Match the most likely changes in the food-web that could account for these data:

reduced effectiveness of the braconid wasp in controlling the aphid population in years 5 & 7	Answer 1
improved effectiveness of the braconid wasp in controlling the aphid population in year 9	Answer 2

answer options for question 1 and 2 are

arrival of megaspilid wasps in the soybean field

arrival of aphelinid wasps in the soybean field

arrival of cynipid wasps in the soybean field

Answer 1

Answer 1 -> Arrival of eynipid wasps in the sojabean Feild. Ariswer 2-> Arrival of megaspilied 'wasp in the soyabean field