Monday, March 21, 2011

A (brief) break

Today is officially the first day of spring break, joy! Well, technically spring break started on Saturday, but that's besides the point. The point is that everyone (most everyone?) gets a week off to relax, go someplace relaxing, and enjoy the weather...or not. I can't put my finger on it, but there's just something off Mother Nature's timing, because it is indeed raining. Again. Or maybe it's because the powers that be in the school system knew of the incoming rainfall and deliberately scheduled break so that it would coincide with these storms. I guess we'll never know.

But never fear because spring quarter is near! I'm excited for my last academic quarter, and the work/fun that the quarter will bring. Looking back, I didn't think that I had done much this past quarter, but looking back at all the work that was done, it was quite an accomplishing quarter. There was the herbivory counting on the shrub sub-samples, all 21 of them), which was followed by going through the full samples and separating them by new and old shrub growth that were dried and massed. Then work with the arthropods come in, starting with measuring the length and dry weight of larvae pre-bird exclosure experiment, and then sorting the post-experiment arthropods. *whew*

So in this upcoming quarter, I'll be continuing the lab work that I've been doing, which includes finishing the sorting of the arthropod vacuum samples and vouchering them as well as picking up the phenology work that I did during the fall. On top of that, I'll be writing my scientific research paper on this past quarter's work and present it at my ESYS symposium in May.

In the meantime, I'll enjoy my opportunity to mentally vegetate for a week and be ready to go starting next Monday!

Thursday, March 17, 2011

And back again

Hello all! Now that finals are over, for me at least, I bring you back to the dry weight of arthropod larvae that I did a while back and publish this post on the comparisons of the bug biomass to its length. But before I get started, some graphs that I ran in R to help illustrate what is going to be discussed.
Figure 1: Here is the original graph when simply plotting out the length of the arthropod larvae to its biomass. Though some details escape the plot, there are 3 points on this graph that show a different type of larvae (dark red circles).
Figure 2: After doing a log transform, this is what the data looks like; much data pertaining to body size are non-linear. There is now more of a distinction between the two types of arthropod larvae. 
Figure 3: Voila! These fit lines better help illustrate the relationship of each type of larvae length to biomass.
And so, we get to the meat of this discussion. To start off, I had collected 37 individual arthropod larvae samples, in which they totaled to about 0.2375g in dry weight. A majority of these samples happen to be of a type of Coleoptera larvae, with the 3 exceptions that were Lepidoptera larvae, and they show that there is a significant increase in weight as their length increases. This appears to be influenced by factors such as body shape, feeding habits (herbivorous or predatory), and the metabolic rate of animals etc[1]. The general idea that can be assumed is that the more an arthropod eats (higher herbivory counts on A. californica), the bigger in mass it becomes, until a certain threshold point. Looking at Figure 1, there seems to be a cutoff value at around 12 mm for arthropod larvae length, which I assume is the maximum size larvae grow to before they are either consumed or pupated. This is useful to know because in such cases, species biomass may reflect functionality more accurately than abundance[2].

It might be more presumable to think that this is due to bird predation because the larger these larvae are, the more conspicuous it is on the sagebrush leaves. This leads to the possible conclusion that there could a top-down effect on the arthropod community, but only on the larvae in the earlier months, and not necessarily on the mature arthropods that appear closer to summer. Maybe the earlier hypothesis that I came up with should also include a comparison of temporal variation of herbivory; it would be interesting to see if the data changes at different times of the year.

1. Sage, R.D. 1982. “Wet and Dry-weight Estimates of Insects and Spiders Based on Length.” American Midland Naturalist 108(2): 407-411.
2. Saint-Germain, M; Buddle, C.M.; Larrivee, M; et al. 2007. “Should Biomass be considered more frequently as a currency in terrestrial arthropod community analyses?” Journal of Applied Ecology 44: 330-339.

Wednesday, March 2, 2011


At least, that's what I think most times I find a new type of arthropod that I haven't seen yet in Lizzie's vacuum samples. She got me started on sorting her bug samples by morphospecies by first going through them and meticulous scanning and collecting them from the trays. I find it rather like a "Where's Waldo?" book, but much more complex and more miniscule. Here are some pictures to illustrate this process:

Just keep searching, just keep searching, just keep searching searching searching...
Bug of interest has been found!
Naturally, this is repeated many times over and it is more eyestraining than looking for herbivory on the shrub samples through the microscope, but I find it much more enjoyable. The only problem with this is that I end up spending too much time on each sample bag combing through the litter for bugs that are sometimes <1 mm large and often in a contorted shape. I am hoping to figure out a tempo for how I look for these critters soon so I can become more efficient at searching and memorizing their features. I also hope to be able to take pictures and make some sort of comprehensive pictionary of these insects, but we'll see how time will work out. There's effectively 1.5 weeks left until finals week, got to get cracking!