The Sawflies
I have collected 51 sawfly over 3 days from a single location. 3 collected 3/31 were discarded due to accidental crushing, leaving 48 larvae. Some had black prickles and some did not, representing different instars. Under a dissecting scope, I noted all from 3/30 have parasites. The parasites vary in size but are all white and oval. Many of the larvae have several parasites. So far there are 4 from 3/31 and 2 from 4/1 that I did not find evidence of parasites. Since collection many have molted, both those with parasites and those that do not appear to have parasites. After molting, I noticed that these later instars do not have prickles. Under the scope, one of the molted sawflies has curled up and has produced a lot of webbed fiber that it appears to be pulling from it's butt. I am curious to see if it will produce a cocoon and if this instar without prickles is the ultimate or the penultimate instar. My hypothesis is that the 4 sawflies that did not appear to have parasites are in fact parasitized but the parasites are either beneath the surface or are maybe smaller and in a location that is hard to see, like beneath a proleg. All sawflies were collected from a group of parking signs. I did not see any larvae in the nearby grass and only noticed 1 on a nearby tree trunk but it was too high up to reach. Some of my hypotheses for why the majority of the sawflies are parasitized:
- collection bias: maybe their behavior of climbing upwards conspicuously is abnormal and is induced by parasitism
- collection bias: maybe parasitism is much higher in this season
- collection bias: maybe the behavior of climbing up a signpost is normal prepupal behavior but the unparasitized sawfly larvae will perform this behavior later or sooner this season
- this sawfly species has an incredibly high rate of parasitism
I am looking forward to seeing what the parasite larvae will become and whether the hosts will be killed or survive. I was hoping to collect non-parasitized sawfly larvae to see which species they become, but I think it is unlikely any sawflies will emerge.
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This is a great experiment! I'm excited to see the outcome. 😊
Update 4/4. the sawflies I collected 4/1 I am keeping in one container because i ran out of individual containers. I clean out the frass and molted skins from every container daily but it seems not enough. 4/3 yesterday I had to remove 2 dead sawflies from the 4/1 collection container so that their rot did not contaminate all the still living sawflies. Yet many were either dead or moribund yesterday. Not certain if this was due to parasitism or poor husbandry. I placed a drop of sugar water in their containers yesterday and many drank. Still, whether housed separate or communally, today 4/4 almost all have died, blackened, and shriveled. Some of the dead have plump oval parasites and some have parasites that seem shrunken or flattened. Those that appear to still be alive: U, Y, (unparasitized) and maybe 3 of the sawflies in the communally housed 4/1 container (parasitized) Today I have not had to remove much frass indicating that soon enough that any living will sawflies will need to either pupate or die. I am hoping that the dead sawflies are dead due to parasites and not poor husbandry and that their death will not kill the parasites. One of the larvae (E) has a big crater in its body I noticed 4/3, but I can't find any wasp in the container. I did find a very long antennae but I think this was just detritus from previous bug captures and I hadn't cleaned the enclosures sufficiently. I hope this crater was just something I had not noticed when I first collected, and not an escapee! The holes in the containers are very very small so an escapee would need to be smaller than the naked eye. I hope that's not the case because my dissecting scope can only magnify so much.
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