Biological Control

This week in lab we observed ladybeetles (Coccinellidae) and their predatory behavior towards aphids (Aphididae). In this particular lab we only observed the functional response of one lady bug at a time. First we observed individually, looking at a petri dish containing a leaf with aphids on it and one ladybeetle. We had to note the number of feedings our ladybeetle did and for how long. Each feeing was noted as an event. Our second task was in groups of four we placed one infested leaf and one uninfested leaf in a box with a glass cover. Then we placed a ladybeetle in and traced its path while timing each action (walking, grooming, resting, feeding). We observed one ladybeetle for five minutes and then repeated the experiment with a second ladybeetle. For both experiments the ladybeetles were starved for one day.

Part 1. 
A functional response has to do with an individual and their behavior, change in response. Type II functional response as the predator increases, the prey attacked also increases until a point where it levels off and plateaus. This point is known as satiation- or the individuals become full. This happens because consumption at some because the number of attacked will remain constant, even as the number of prey increased. Variables that determine the level of the plateau is the carrying capactity. Other factors would be the density of the prey and predators, space, and environmental conditions.


For experiment 1, with the individual ladybeetle observed under a microscope, I observed six events. I classified each event as when the ladybeetle first picked up the aphid to begin feeding. I ended each event when either the aphid was fully eaten or in a couple of cases the ladybeetle "spit" out the aphid after chewing on it until the aphid was dead. Below are my results, the time was recorded in seconds. The feeding behavior of my ladybeetle was interesting, it would eat one really fast and then it seemed to take its time with the next, and then eat another one really fast. It only ate apterous adult aphids as well.

Experiment 1
Event #	Feeding duration (seconds)
1	21
2	144
3	4
4	242
5	284
6	31

The mean feeding duration for the ladybeetle was 121 seconds, and the standard error was 49.5. These results do not compare very closely to the table in the lab handout for a couple of reasons, the first being that the insects in the handout table too much longer than the ladybeetles to have one event (the time was measured in hour compared to seconds) Also, the insect in the table went after all life stages while the ladybeetle I observed only appeared to be going after adults. A lot of the time for my ladybeetle was spent either eating, walking or grooming. Grooming is particularly important to insects to avoid diseases.

I really enjoyed this experiment because I have never seen ladybeetles under a microscope eating aphids. I was surprised by how long sometimes my ladybeetle just sat there with an aphid in it's mouth not eating, it just looked like it was holding it. I think that ladybeetles would be a good biological control agent in the field, but aphids outnumber them by a lot. So since this ladybeetle was starved for a day, and only ate six aphids in the 30 minutes I observed it, you would need A LOT of ladybeetles to mitigate an aphid population.



Part 2.

My group consisted of myself, Denae, German, and Matt. My job was to trace where the ladybeetle went on the glass. The results of the experiment are below.

Experiment 2
Beetle #	Action	Duration (seconds)
1	walking	62
1	walking	18
1	walking	41
1	walking	6
1	grooming	64
1	grooming	7
1	grooming	24
1	grooming	29
1	resting	34
1	resting	15
1	feeding	0
2	walking	51
2	walking	31
2	walking	4
2	walking	7
2	walking	21
2	walking	7
2	grooming	9
2	grooming	12
2	grooming	22
2	grooming	26
2	grooming	92
2	resting	18
2	feeding	0

On average the beetles spent the following:
24.8 seconds walking with standard error 6.54
31.6 seconds grooming with standard error 9.41
22.33 seconds resting with standard error 5.89
no time grooming










Ladybeetle #1 was a male and ladybeetle #2 was a female. Both of the ladybeetles had random paths. They both wandered around the center a bit but stayed on the sides (see pictures above). Neither of the ladybeetles found the aphids to feed on, however, they both did walk right by them. I did find this surprising after knowing that they hadn't eaten for a day.

I think this experiment showed just how difficult this would be to use in the field because if they beetles couldn't find the aphids as food in a small box, they might be more difficult in nature to find. These results were also not very comparable to the table given to us being that the ladybeetles never found the aphids, so it is hard to compare.