Wax Worm/P. larvae LD50

From 3-14-15.

It has been seven days since the early instar wax worms were fed BAD spiked with P. larvae spores. Started on 3-3-15. The raw survival data is saved to an Excel file, but the data is also displayed in the two tables below. Statists were calculated as three replicates of 10 wax worms each.

Raw data results

Normalized data to give percent survival

Concentration of spores that were put onto each plate (taking into account the 100 uL volume)

1:5 = 2000 spores

1:25 = 400 spores

1:125 = 80 spores

The above concentration of spores were added to each container with 10 early instar wax worms in each container. So, it is likely that each wax worm only ingested about one tenth of the concentration above.

Discussion:

Early instar wax worms that were fed the only the BAD without spores had only about 78% survival after seven days, which isn't that bad, but not as good as it should be or I'd like it to be. I believe that the low survival is due to the small storage container that was used. There were 10 wax worms in each small container and the container eventually filled with feces and other debris. Interestingly, the wax worms will eat organic matter, including each other. This is especially evident when there are different sizes of wax worms present in the same container. On one day a wax worm was completely missing from the container when I checked survival. There was no sign of it anywhere and I am absolutely sure it did not escape, however, the container was full of early instar wax worms that were about three times the size of the missing wax worm. I cannot confirm its fate, but I believe it was eaten either to a diseased state making it more vulnerable, or just simply being a runt of a wax worm.

There was a trend of survival seen depending on the amount of spores that the wax worms were fed. The 1:5 dilution resulted in the most deaths and at the quickest rate and so on. However, the error bars indicate that this trait is not statistically significant, meaning there was no distinction between the amount of spores given (1:5 to 1:125) and the survival rate. It is also evident that I should have gone longer beyond seven days to check survival and will likely do so in the future.

I will attempt this experiment again in the future, hopefully with more early instar wax worms and a higher concentration of spores. I need to find a way to categorize the instars of the wax worms and then sort them for the experiment.


LD50 Injection
I checked the late instar wax worms that were injected with P. larvae and B. thur spores yesterday. All of the wax worms that were injected with B. thur are now dead. Pictures of what they looked like only ~18 hours after injection are seen below. They were non-responsive when prodded with a forceps and visibly look dark and deceased. These wax worms were injected with 4x10^5 B. thur spores, which is a very high concentration.

WW injected with Bacillus thuringiensis after one day.

WW injected with Bacillus thuringiensis after one day.

After the above wax worms were disposed of, I realized that maybe they were not dead, but in fact have begun of pupating... It could be that after injection of the B. thur spores triggered pupation in the wax worms. I will most likely repeat this experiment using B. thur as a positive control, albeit at a lower concentration.


//EWW