When Trees Weep

 Entomology, Insects, Natural History, Photography  7 Responses »
May 112011
 

A few days ago I was walking through the University of Guelph Arboretum taking some down time and trying to get back into the photography groove when I noticed a peculiar sight…

 

Tree weeping sap covered in insects

The trees were weeping, and dozens of flies were lapping up the sweet, sweet tears! Since there were several of these patches on two nearby trees (my tree bark ID skills are severely lacking, I’m a leaf man) and the wet marks were 4 to 10 feet off the ground, I felt it was a safe guess that it wasn’t a territorial marking (unless the UofG men’s basketball team was having a summer camp…), and last I checked I wasn’t in Fangorn Forest, so I did a little detective work to discover the story behind the sadness.

Closer inspection revealed these curious holes:

Yellow-bellied Sapsucker holes drilled into tree bark

My first thought was to scan for long-horned beetles (Cerambycidae) or perhaps metallic jewel beetles (Buprestidae), but after seeing nothing but flies and wasps, I took a closer look and noticed that the holes only pierced the bark, and not the xylem (aka sapwood). It dawned on me that what I was looking at was a tricky, sticky lure set by a bird I’d seen plenty of times before in the Arb; the Yellow-bellied Sapsucker (Sphyrapicus varius). This crafty woodpecker will cause superficial injuries to a tree, and then sit back while the sap flows free. The bird will then return to the tree and pick off the insects which are feeding on the sap, as well as some of the sap itself! Clever bird…

Pretty cool biology, so I took the opportunity to see what sort of insects were at risk of becoming an early spring brunch for the hungry sapsucker.

I observed a few butterflies when I first approached the trees, but they quickly flitted away, not to return while I was there. I’m by no means a Leper (i.e. a Lepidopterist), but I think they may have been Red Admirals (Vanessa atalanta, Nymphalidae), which are one of the earlier butterfly species to be found in Southern Ontario.

There were a number of hymenopterans taking advantage of the Saturday afternoon bounty including many Ichneuomoid wasps and this fuzzy female:

Andrenid bee eating tree sap Andrenidae

This andrenid bee (Andrenidae) seemed quite content to sit and lap up the sugary sap running down the tree bark, not caring when I moved in and out trying to get a decent photograph of it’s amazing hairdo.

Tenthridinidae wasp eating tree sap with a calliphoridae and muscidae fly

While the bee was busy enjoying a solitary meal, this sawfly (Dolerus unicolor, Tenthredinidae) was more than happy to share the sap with a couple of calyptrate flies (a blowfly [Calliphoridae] on the right and what I believe to be a Muscidae at the top). In fact, the calyptrates made up the vast majority of the insects visiting the tree, in some places packed so tightly you couldn’t see the tree for the flies!

Blow fly Calliphoridae sponging up tree sap

The sponge-like mouthparts found in many calyptrates are well demonstrated in this blowfly (Calliphoridae, possibly subfamily Chrysomyinae). You can see the maxillary palpi sticking straight ahead as the membranous labrum and associated sclerites mop up any residual tree sap on the bark.

Scathophaga sp. Scathophagidae

Another, lesser known calyptrate family was also making an appearance; the Scathophagidae. I could make out what looked to be two species of scathophagid, including this Scathophaga sp. perched nearby awaiting its turn at the sugar shack.

Tachinidae fly on tree drinking tree sap

Not everything went according to plan on this outing however, as I made a major n00b move – I forgot to pack specimen vials! While normally I’d have a dozen or so snap-top vials in my camera bag in case I ran into something which needed to be examined at a later date and added to the University of Guelph Insect Collection, after transferring my photo equipment into my new camera bag (courtesy of the best wife ever), I neglected to throw in the vials! The first rule of entomology (besides “ALWAYS talk about entomology”) is to collect the damn specimen, and as luck would have it, I came across a fly which I instantly wanted to collect (pictured above & below).

Tachinidae with tree sap fly

This Tachinidae caught my eye right away, and after several attempts, I managed to get a couple of decent images. Unfortunately, tachinid flies are one of the most diverse groups of animals on the planet, and the specimen would be vital in identifying it to the genus or subfamily level on my own. A lesson learned, and needless to say I threw a couple of vials in my bag as soon as I got home!

After getting my fill of photos and not having any means to collect some specimens, I decided to pull back and let nature take it’s course. While I never saw the sapsucker, I certainly appreciated the opportunity it created, allowing me to photograph a great diversity of flies and wasps!

The Blow Flies of Eastern Canada

 Entomology, Insects, Publication  3 Responses »
Jan 112011
 

The Canadian Journal of Arthropod Identification has just published it’s 11th edition and features the blow flies (Calliphoridae) of eastern Canada. This new paper includes richly illustrated keys to the adults of all genera found in eastern North America and the species found in eastern Canada (excluding the cluster flies (Polleniinae), and the rare, mollusk-parasitizing Melanomyinae). Additionally, two species are newly recorded in Canada (or eastern Canada), and Stephen Marshall has populated the paper with his world-class photographs.

Lucilia sericata Calliphoridae Blow Fly Common Green Bottle Fly

Lucilia sericata, the common green bottle fly

The Calliphoridae are important for a number of reasons, and unlike many insects, correct identifications can quite literally be a life or death choice. These flies are a keystone in forensic entomology, and knowing which species colonize a victim’s body, and when, can mean the difference between catching a killer and convicting the wrong person. The importance of Ontario Calliphoridae is perfectly illustrated in the case of Steven Truscott. Sentenced to death by hanging at the age of 14 for the murder of Lynne Harper in rural Ontario, Truscott’s sentence was commuted to life in prison in 1959. Truscott served his 25 year sentence behind bars, and lived with the stigma of a being a convicted murderer for nearly 50 years. It wasn’t until an appeal before the Ontario Court of Appeal in 2006 that entomological evidence collected at the time of the murder was analysed and presented by Dr. Sherah VanLaerhoven of the University of Windsor. This entomological evidence, largely composed of blow fly maggots, helped to overturn Truscott’s conviction, and led to his acquittal. Sure, forensic entomology wasn’t even on the radar in 1959 (although the coroner at the time had the presence of mind to collect and catalog maggots from on and around the body), but forensic entomologists today are called to hundreds of crime scenes every year to help develop a timeline of events to be used in criminal prosecution.

The majority of people using this paper will not be making these life or death decisions, but being able to identify the species you find on your backyard flowers (because blow flies are also major pollinators) is equally important. Plus, if you choose to play CSI on that dead squirrel under the deck, now you can!