Norfolk Naturalist

Introduced Pine Sawfly

Diprion similis

Diprion similis larva at Algonquin Provincial Park, September 2019.

Sawflies are a group of insects that many people haven’t even heard of. Part of the reason is because, in appearance and behaviour, they are like a hybrid between two major groups: their larval stages look like caterpillars (larvae of Butterflies and Moths ie. Lepidoptera), and their adult stages look like bees or wasps (Order Hymenoptera). Despite appearances and lifestyle, it is the latter category that they actually fall under: Hymenoptera which also includes the Bees, Wasps, and Ants. The major features that set sawflies apart from their relatives is that they eat plants, and they don’t have the constricted “wasp waist”. You might find this a little confusing, as Bees certainly don’t have an obviously thin waist, but they actually do have a constriction between their thorax and abdomen, it’s just more difficult to see than in many wasp species.

Like many insect Orders, the name Hymenoptera refers to a distinct aspect of the members’ wings (‘ptera’ is derived from the Greek for wing). Hymenoptera doesn’t have an easy translation though, like say Diptera for the True Flies (di = two, ptera = wings). The beginning part of the word is either from the word “hymen” which means membranous, or from the word “hymeno” which refers to the Greek God of Marriage. Hymenopteran wings are membranous, but they also have tiny hooks that link their fore- and hind-wings, meaning that they could be said to be “married” wings as well (Grissell, 2010). Whatever the case, the group is one that includes thousands of species of wasps, bees, ants, and of course, sawflies.

The common name “sawfly” is describing the way the female sawfly lays her eggs. Instead of a stinger or stinger-like ovipositor (egg-layer) at the end of her abdomen (like most of the other Hymenopterans), the female sawfly has a saw-like ovipositor, a cutting tool that she uses to open up plant tissue, and then inserts her eggs within.

This is what the Introduced Pine Sawfly (Diprion similis) does to pine needles. D. similis prefers White Pine (Pinus strobus) as its host plant (in North America), but will lay eggs and successfully grow to maturity on several other pine species. The female lays about 10 tiny eggs inside a pine needle (Cranshaw, 2004). After inserting the eggs, the female seals them in with a secretion that hardens for protection (Wagner and Raffa, 1993). The larvae that hatch from the eggs begin to feed on the pine needles. For the first part of their life, they will remain together but begin to disperse as they grow older. These larvae prefer to feed on needles that are at least 1 year old, probably because the younger needles are full of more toxins (Wagner and Raffa, 1993). As they consume needles, they grow, from 2.5 mm long upon first hatching to almost 3 cm before the larva is said to be “mature”. They don’t grow continuously, but rather have to molt and enter a new size class each time they’ve gained enough nutrients. For female larvae, they have six growth stages between molts and the males have five (CABI, 2020).

During this time, you would be forgiven for thinking they were caterpillars, because they look very similar. The way to tell caterpillars from sawflies is to count the number of legs. Their first set of legs will be six, and jointed for both groups, but they will also have a number of legs behind these called “prolegs”. If the larva you’re looking at has more than 5 pairs of prolegs, it’s a sawfly. Another giveaway is the distinct single eyes of sawfly larvae, as opposed to tiny ocelli (miniature eyes in clusters) in caterpillars.

A *Macremphytus* sawfly larva. The head is to the right, behind it is the first three pairs of true legs, then behind those are a series of lumps that denote the pairs of prolegs, which number at least 8 (so more than 5).

Once they’ve reached their final larval stage, they spin a cocoon around themselves with silk, and transform within. Diprion similis larvae prefer to form their cocoons in the pine trees where they feed, rather than on the ground like many other sawflies.

In Europe and most of North America there are two generations per year, which means that what happens next depends on what time of the year it is. If the larvae have grown enough and created their cocoons in the summer, they will develop within in about 2 weeks into adults, but if they have reached this point near the end of fall, they will enter diapause (essentially insect hibernation) for several weeks before emerging in the spring (CABI, 2020). When they emerge, the adult sawflies are entirely different creatures, just as butterflies and moths are very distinct from their caterpillar young. The adults have wings, and with these they search for mates.

Adult Male D. similis, displaying the feathery antennae used to track down a female (Photo credit: Scott R. Gilmore.)

Males are attracted to females by pheromones (a chemical signal between members of the same species), as one would guess by the male’s elaborate antennae. The males can be attracted to a female across 61 m of open field, which is a great distance for an insect only a matter of centimeters long (Wagner and Raffa, 1993). Once mated, the female lays eggs in pine needles, and we are back at the beginning of their life history.

One note about mating: it isn’t necessary for the female to mate to be able to lay eggs. She shares with the other Hymenoptera a bizarre (to us) chromosome setup known as haplodiploidy. Females have one set of chromosomes (the mother’s) and males have two (mother and father). What this means in practice is that a female sawfly can lay an egg that will develop into a fully functional male offspring without ever going through the trouble of mating. This has implications for the spread of such organisms, as not all members of the population need to pair up to contribute to the next generation.

Which brings me to my final discussion of this species: they are commonly referred to as the Introduced Pine Sawfly because they were accidentally introduced into North America from Europe, likely in plant nursery stock imported in 1914. They have become well established in North America since then. Thankfully, they only very rarely reach a high enough population density to be considered an “outbreak” invasive species, and though they feed on tree leaves (needles), many predators and parasitoids feed on them (Wagner and Raffa, 1993).

The last time we were camping at Algonquin Provincial Park, I encountered quite a few of their larvae likely because they were in the fairly mobile phase before finding a spot to spin a cocoon (it was the end of September, the beginning of October). They may be an introduced species, and they may feed on White Pines, defoliating some of the branches, but as with any organism, they have a story all their own, and I think it’s worth telling.

Diprion similis larva hanging onto the end of a pine needle in Algonquin Provincial Park.

References:

Wagner, Michael R. and Raffa, Kenneth F. Sawfly Life History Adaptations to Woody Plants, 1993.

Cranshaw, Whitney. Garden Insects of North America. 2004.

Marshall, Stephen. Insects: Their Natural History and Diversity. 2006.

Grissell, Eric. Bees, Wasps, and Ants. 2010.

CABI, 2020. Diprion similis. In: Invasive Species Compendium. Wallingford, UK: CAB International. www.cabi.org/isc.

Tags algonquin provincial park, diprion similis, ecology, macrophotography, Natural history, nature, ontario, sawfly

book review

Pterosaurs, by Mark Witton

Post author By hiebertjeffrey
Post date January 7, 2020
5 Comments on Pterosaurs, by Mark Witton

Anyone who finds fossil animals fascinating will be delighted by this book by Mark Witton. The science is well-explained, yet in-depth, and the illustrations (photographs of fossils, skeletal reconstructions, and paintings) are incredible.

Pterosaurs begins with several overview chapters to bring the reader up to speed on the basics of pterosaur anatomy and terms, demonstrating some of what we know and what we don’t know about these flying reptiles. The majority of the book details each pterosaur group with a chapter. Here you will familiarize yourself with the ornithocheiroids, pteranodontians, and dsungaripterids. As with many dinosaur names, some of the scientific nomenclature can be a bit tongue-twisting, but by reading this book you will begin to tease apart the differences between pterosaur groups and so become more apt to recognize the names even if you have trouble saying them aloud.

Each pterosaur group chapter has a history of the group’s study, an overview of their anatomy (often highlighting differences and similarities between other groups), hypothesized locomotion (how each group of pterosaurs moved both on the ground and in the air), and ideas about the group’s ecology in the Mesozoic. The history of study was often interesting, seeing how a pterosaur group’s identity changed with new fossils or new ideas about old fossils. The anatomy sections are a bit difficult for myself to get through because I’m not a paleontologist and had to often reference the anatomy overview chapter at the beginning of the book. With the overview diagrams’ help, I was able to comprehend most of what was being described, at the least I was able to recognize the major differences between groups that were being highlighted. The sections on locomotion were fuel for the imagination, conjuring images of how these ancient creatures actually moved through their environments. Witton would often compare each groups’ purported flying ability to a modern group of birds to better convey their distinctive flying style. Of course much of this and the ecology sections are speculation, but Witton provides lines of evidence for and against various flying and feeding modes that have been suggested which brings to light what we know and what we don’t about how these animals lived. The ecology sections are my favourite because I love to imagine the animals as part of the Mesozoic environment, living their lives alongside the plants and animals of their time.

Along with the informatively dense but readable text are the illustrations which are amazing. For each pterosaur group there is at least one skeletal reconstruction of a species along with a fully realized painting of them launching. Besides these, there are photos and drawings of particularly well-preserved fossils. Accompanying each chapter is at least one full-page painting of a scene from the time of the pterosaurs, whether it’s Pteranodon diving into the ocean after a bait-ball of fish, or a Rhamphorynchid investigating a Jurassic snail. These paintings are wonderful at giving life and colour to the fossils and placing these creatures in their setting.

Sprinkled throughout the information-rich text is humour. My personal favourite is a caption for a painting of Azhdarchids which describes them as fleeing the next chapter about pterosaur extinction.

All in all, the book is a wonderfully informative, beautifully illustrated volume, full of descriptions and context for a group that doesn’t get as much press as the Dinosaurs. After finishing this book, you’ll be convinced that pterosaurs were an amazing and unique group of fossil animals as well, that deserve to be treated with the same amount of awe and wonder.

Tags book review, Fossil, Mark Witton, prehistoric life, Pterosaur

Nature Observations

Pinery Birds, Winter 2019

Post author By hiebertjeffrey
Post date December 22, 2019
10 Comments on Pinery Birds, Winter 2019

Pinery Provincial Park is a great place to visit any time of the year, and Winter is the season when you can get closest to a few of the bird species that make their home there.

We always bring along bird-seed to Pinery when we go in the Winter, because there are a number of birds that will come very close when presented with a nutritious food supply. Some (Black-capped chickadees and White-breasted nuthatches) can be induced fairly quickly to landing on your hand and feeding from it. This year, we were a bit early in the season and most of the birds except a few brave chickadees were too wary to feed from our hands. Despite this, we were able to feed many birds by leaving out a pile of seeds on the railing on our site (we were staying in one of the yurts they have there). If you’re planning to do this yourself, remember to not leave the birdseed out overnight. During the day, you will attract small foraging songbirds but at night, you’ll most likely be feeding raccoons, who can devastate snapping turtle populations in the park, if they overpopulate themselves.

The first birds we attracted to our food supply were the bold chickadees, ever-eager to exploit any opportunity available.

A perched Black-Capped Chickadee (*Poecilie atricapillus*)

Next came the nuthatches, with their impressive ‘talons’ which they use to grip bark as they scale down tree-trunks to pry out insect food.

White-Breasted Nuthatch (*Sitta carolinensis*)

Tufted titmice were quite abundant as well. I’ve never been able to feed one from my hand, but they were quite content to fling seeds about in the pile, picking out the ones they desired.

The final visitor to our railing was a downy woodpecker. Downys are the smallest woodpeckers in Canada, at approximately 15-17 cm (Backhouse, 2005). Still jabbing as though he were piercing bark, the woodpecker walked awkwardly along the railing. It truly appeared strange to be perched and moving horizontally, as they are so superbly adapted for their vertical orientation on tree trunks.

Downy Woodpecker (*Dryobates pubescens*)

Although only a few landed on our hands to pick at seeds, we were pleased to see these little birds foraging nearby, bringing cheer to the wintry woods of Pinery Provincial Park.

The view of the seed pile being visited by the winter birds.

References:

Backhouse, Frances. Woodpeckers of North America. 2005.

Tags Birds, nature, ontario, photography, Pinery Provincial Park, Woodpecker

book review

Flora of Middle-Earth

Despite paying a lot of attention to the little invertebrates that scurry about in the undergrowth, I tend not to pay too much attention to plants. This isn’t on purpose, or because I dislike them for any particular reason, but I think it’s difficult for us to look at them in the same way that we look at animals because they don’t move about (on the same timescale or in the same ways) and they don’t seem to display varied behaviours. If we can move past these false ideas about plants we may realize that life doesn’t flourish against a green background, but rather, the drama of life plays out amid the foliage and thorns and seeds and roots just as much as it does amid the fur and feathers, claws and teeth.

One book that has opened my eyes to this world of green, growing things is Flora of Middle-Earth by Walter S. Judd and Graham A. Judd.

I have been an avid fan of Tolkien’s mythos and the science of living things for most of my life, so when I found this book, I felt that it had been written specifically for me. What really drew me to the book was that it was written by a world-renowned plant scientist and this knowledge shows through details of plant biology and ecology within its pages. The book succeeds on both a scientific and a literary level, as the author and illustrator understand plants and Middle-Earth extensively. They even draw on the History of Middle-Earth series which are unfinished manuscripts by J. R. R. Tolkien put together by Christopher Tolkien, to fill out the botanical landscape of this fictional, yet powerful world. The first chapters give an overview of plant biology, evolution and ecology, as well as outlining the biogeography of plant ecosystems in Middle-Earth throughout its known history (First to Third Ages). After this, there is a chapter that contains a key to identifying the plants that are detailed through the majority of the book so that if you encountered a plant in our world you could follow the descriptions to its genus or species. This section isn’t particularly useful in my opinion because although Tolkien mentions over a hundred plant groups within his legendarium there are many more plants that exist, so that you could very easily follow the keys to a dead end. Next is a chapter devoted to the two most important plants in Middle-Earth: Telperion and Laurelin, the Two Trees of Valinor. This was interesting, seeing where Tolkien might have drawn his inspiration for the fictional Trees from plants that exist in our time and place.

Following this is the largest section of the book which runs through over 140 plant types mentioned in Tolkien’s writings. For each plant, there is a quote containing a mention of it, a general overview of its place within Middle-Earth ecology and culture, a study of the plants names (how Tolkien can you get?), a description of the plant’s ecology and biology in our world, a mention of its place in human culture and a botanical description of its form. Alongside this impressively detailed treatment, many of the plants receive a woodcut-style illustration which shows them in the context of Tolkien’s stories and world.
The final chapter is a Note from the Illustrator, so if you’re interested in this book primarily for the artwork, there is a description at the end of how and why he created the illustrations the way he did.

Part of what enhanced my appreciation of the book was reading it while in Algonquin Provincial Park, a place filled with memory and meaning for myself, just as Middle-Earth is. Reading about a plant’s place in Tolkien’s writings while encountering some of the same plants in Algonquin Park was an experience that is a microcosm of what is so special about this book and the Tolkien legendarium as well. Tolkien’s writings shed a new light on the world around us, just as this book sheds light on a piece of that world (Middle-Earth) and our own world.

The greatest accolade I can give this book is that I learned a lot about Tolkien’s Middle-Earth and the ecology of plants in our own world. If you’re interested in either of those things, I would highly recommend this excellent, beautiful book.

Tags book review, botany, ecology, flora, middleearth, plants, tolkien

Species Profile

Eastern Band-winged Hover Fly

Post author By hiebertjeffrey
Post date December 8, 2019
3 Comments on Eastern Band-winged Hover Fly

Ocyptamus fascipennis

Ocyptamus fascipennis adult, spotted at Algonquin Provincial Park, August 2019

When you’re interested in insects, you’re always going to be running into something new. There is always one more creature that you have never seen before, one more behaviour you haven’t heard of, and that’s because insects are incredibly diverse. Today, I’m going to pick out just one of the many species of insects to zoom in on, and explore its story.

The species I’ve chosen is Ocyptamus fascipennis, or the Eastern Band-winged Hover fly. Let’s start from the top: Ocyptamus fascipennis is a “True Fly”, a member of the Order Diptera, which is a division of the Class Insecta. Diptera means “two wings” which gives you the easiest way to identify this group of insects when you encounter them. Almost all insect groups have 4 wings (two pairs) but these pairs of wings have been modified into very different structures in different lineages of insects. For the True Flies, one pair of wings still provides lift and flight, while the other has been reduced into tiny knobs known as halters. These reduced wings act as stabilizers, giving the flies the ability to perform aerobatic feats of agility (as I’m sure we’re all familiar with in House Flies (Musca domestica)). The halters of Diptera are more than just balancing beams, they’re actually sending complicated signals to the fly about its aerial position.

Ocyptamus fascipennis is part of a Family of True Flies called Hover Flies, or Flower Flies (Family Syrphidae). The Syrphids are common insects in gardens where they feed on nectar and pollinate flowers. Because of this habit, many species of Syrphids have taken on the appearance of more conspicuous flower visitors such as bees and wasps, in order to gain some protection from the classic warning colours of black-and-yellow stripes. O. fascipennis in particular seems to mimic solitary wasps or types of parasitoid wasps with its elongated and narrow abdomen.

So far, we’ve been talking about adults of these flies, but all insects go through multiple life stages, some more dramatically varied than others. Diptera undergo holometabolous growth which is a fancy way of saying that they have life stages that look very different from each other and one of those stages is a transformation phase which is mostly immobile. When young hoverflies (larvae) hatch from eggs, they look very different from the adults landing and lifting from flower petals in gardens. Larval O. fascipennis have no wings, and no legs, and are sometimes known by the name that many fly larvae receive: maggots. O. fascipennis larvae don’t consume garbage or dead animals, but instead are active predators, squirming across leaves in search of their prey: aphids.

Stephen Marshall, in his incredible book about Insects describes Syrphine larvae hunting as this: “at night they move blindly among the aphids, grasping victims using typical maggot mouth hooks, then holding the doomed aphids up off the surface to consume the body contents.” (Marshall, 2006).

A Syrphine larva hunting a herd of aphids (photo credit: Christine Hanrahan)

It seems then that Flower Flies are very beneficial insects to have in the garden. They provide pollination for flowers, and their larvae consume plant-eaters such as aphids and related scale insects.

While I was unable to find very much information pertaining to Ocyptamus fascipennis specifically, one other member of the genus deserves special mention because of its interesting larval habitat: tank plants (Bromeliaceae). The Central American and South American species of Ocyptamus that inhabit these confined aquatic habitats (pools of water within the plant itself) ambush and consume other aquatic insect larvae that live in the plants alongside them. The larvae are even thought to use a paralyzing venom to subdue their prey (Rotheray et al, 2000).

All in all, Ocyptamus fascipennis and its relatives are fascinating flower flies with intriguing habits. I hope you’ve enjoyed taking a closer look at them today.

UPDATE NOVEMBER 2021: Near Point Pelee, Ontario, individuals of Ocyptamus fascipennis were observed apparently migrating. The flies were observed moving East to West along with several other insects including tens of thousands of potter wasps (Ancistrocerus adiabatus) (Skevington and Buck 2021). The authors of the paper note that insect migration is a largely understudied phenomenon, especially in North America, so further study is needed to figure out the details.

References:

Rotheray, G. E., M. Zumbado, E. G. Hancock and F. C. Thompson. 2000. “Remarkable aquatic predators in the genus Ocyptamus (Diptera, Syrphidae).” Studia Dipterolologica 7: 385-98. (full text available here: https://repository.si.edu/bitstream/handle/10088/17095/ent_FCT_89.pdf?sequence=1&isAllowed=y )

Marshall, Stephen. Insects: Their Natural History and Diversity. 2006.

Marshall, Stephen. Flies: The Natural History and Diversity of Diptera. 2010.

Skevington, Jeffrey H., and Buck, Matthias. 2021. “The first documented migration of a potter wasp, Ancistrocerus adiabatus (Hymenoptera: Vespidae: Eumeninae)”. Canadian Field-Naturalist 135 (2): 117-119.

Tags biology, flies, insect, macrophotography, nature, ontario, syrphidae

Uncategorized

Welcome to my new Nature Blog

Post author By hiebertjeffrey
Post date November 30, 2019
No Comments on Welcome to my new Nature Blog

If you’re interested in the living things that inhabit this world with us, then you’ve come to the right place. I’ve always found it fascinating that there are so many different kinds of creatures, living out lives in different ways to us humans. In some cases, it’s difficult to believe that we share the same planet, let alone the same backyard. There are countless species that surprise and delight in your own neighbourhood, and there are many more around the world. I’d like to explore this diversity, and try to share my own excitement about these creatures, whether they are insects, fungi, plants, birds, mammals, or any of the other species that crawl, fly, swim, run or grow across the planet.

To do this, I’m planning on producing posts detailing a specific species or group of species to get a taste of what sort of creatures are out there. I will also occasionally post about my own observations (and photos) of species that I’ve encountered in my own travels in Southern Ontario. Another thing I’d like to do is review books that are relevant to learning about nature, as I have a personal library stocked with some great books about the diversity and wonder of life.

I hope that when you visit this blog you learn a little something, gain a greater appreciation for living things, and get inspired to pay a little more attention to the world of nature that’s all around us.