Journal #5
USA, Hawaii, Honolulu Country, Mililani, 95-1096 Auina St., Elev: 880 ft., 5 May 2020, Coll: C. Deptula
Method: Active Observation.
Time: 4:00-5:30 PM.
Today I decided to hang out outside and just observe some organisms around my backyard without trying to disturb them with iNaturalist photos or collecting, as I am done with my collection (I’ll give the insects a brief respite before I go out and collect more)! It was a sunny (only a few clouds), very warm day at 86 degrees F. However, where I was looking was mostly shaded by the tall eucalyptus trees behind my yard. There were occasional, strong gusts of wind.
While walking around outside, I noticed a large number of flies congregating around a dead gecko (that my dog probably killed and left to rot). The smell told me why there were so many flies as it smelled very strongly of death and decay. The gecko was at the base of a bottle palm and was surrounded by various types of ferns. I saw something similar a week or two back with another dead gecko, but there was more fly diversity today. I saw numerous Calliphora flies, around 10-15 which would hang out on vegetation around the gecko and occasionally jump onto the dead carcass. There were also the usual houseflies (Muscidae), around 5, through these were smaller and harder to count, and also a few green colored blow flies (Calliphoridae). Included in this group was numerous small gnats and minute flies that I would occasionally see. However, what surprised me the most was a large flesh fly (Sarcophagidae), which proved to be very elusive to spot. I saw it land on the rock wall near the gecko, but not on the gecko itself. This could be because of the other flies, but also, I may have disturbed it by being there. It had large red eyes, hairy legs, and grey and black alternating longitudinal stripes along its thorax. It also had large hoof-like feet. This fly was very noticeable as it was .5 inches to .75 inches long —easily one of the largest flies I’ve ever seen behind the tachinid I found at Blodgett forest. Because of this, I was disappointed I didn’t have my net! I was getting grossed out by the smell though, so I tried to move away. Doing so caused most of the flies to scatter, especially the Calliphora flies, which I’ve observed previously.
Poking around some of the dead fern leaves in my yard, I was able to find some interesting things, though no new insects (I haven’t been able to find many insect decomposers in the leaf litter since coming to Hawaii, I’ve mostly seen isopods). The only insect I was able to find besides some Yellow Crazy Ants (Anoplolepis gracilipes) crawling on the soil’s surface, were numerous small Surinam roach nymphs. I remembered these well growing up as they’d always crawl up your legs at public parks, or while you were playing at soccer practice. I don’t quite remember so many being at my house though! These are cool since they can also reproduce parthenogenically. The most interesting thing I was able to find was a giant red centipede (most likely Scolopendra subspinipes). This moved relatively slowly so I was able to run inside to get my camera and grab a photo of it, unlike the flesh fly. The reason I did so was because of how remarkable the size of the centipede was, it was easily 8-9 inches long. So, although it was not an insect, this made observing very interesting. It also got me wondering what this centipede eats—probably a lot of isopods and roaches, but maybe these introduced centipedes have impacted a lot of ground dwelling insects as well? I do not know the ecological impact of these invasive centipedes, but to maintain their large size I’m sure requires a large appetite.
Species list:
10-15 Calliphora flies (Blue-green color)
Numerous small, unidentified gnats
1 large Sarcophagidae
5 Muscid house flies
3 green Calliphorids
1 Scolopendra subspinipes
Numerous Anoplolepis gracilipes
Numerous Pycnoscelus surinamensis
Species Account:
It was interesting to see how the Calliphora flies would react to movement. I mentioned in a previous observation how they sound like bees, but these flies are much stronger and more agile flyers than bees, and their flight pattern is rather erratic, involving flying in circles before landing. Would this be to perhaps gain more depth perception of their surroundings? I’ve heard that wasps are known to hover and fly back and forth in order to paint a better picture of its surroundings. Given that the Calliphora flies don’t have much separation between their compound eyes, I can see that a behavioral adaptation to overcome this physiological drawback would make sense evolutionarily! Unlike many other insects, these flies also have red eyes, which is interesting to see. They also lack pseudo pupils which indicates to me that the flies are not absorbing all the visible wavelengths of light for humans. For example, my mantis has black pseudopupils and green eyes—the green may just be due to pigment, but the pseudopupil is clearly due to ommatidia absorbing light. Are the flies rejecting all red light, and if so, why? Also, why is it that these flies don’t seem to be absorbing visible light, or at least aren’t showing it with pseudopupils? These flies are quite big, so it was easy for me to see these details. Based on their quick reflexes, whatever the evolutionary logic behind their current anatomy, it’s apparent their eyes are serving their function! I tried to agitate the flies more to see how they would fly, but I mostly just scared them all off. When they did try to come back, I noticed that while the house flies would dive head first into the dead gecko, the Calliphora flies would mostly all ease back towards the carcass by perching on vegetation around it and flying to closer and closer perches before also landing on the gecko. At any given time, most of the Calliphora would be perched, not actively eating/laying eggs on the dead creature. These flies are certainly interesting and entertaining insects, though they are also quite frightening because of their speed and the loud noise they make while flying (also they were all just landing on a dead lizard, and were getting close to my face—yuk)!
