Field Guide to May 2021

Catkins

By Julia Pupko

Ever notice the long, worm-like structures hanging from trees such as birches, aspens, and cottonwoods? These structures are known as catkins. Catkins are actually made up of small, wind-pollinated flowers. Trees with catkins can be monoecious like birches (one tree carries both male catkins and female flowers) or dioecious like Eastern Cottonwood (Populus deltoides) (male catkins and female flowers are on separate trees).

Catkins of many species are present over winter, they are just closed. When warm weather arrives, the catkins begin to open and flower, releasing pollen for their female flower counterparts. Catkins usually open and mature before the leaves, reducing the chance that the leaves will get in the way of pollination. Keep your eyes out for these short-lived beauties this spring—they are already open and pollinating!

Phenology Fumble

By Julia Pupko

Climate change has certainly been affecting Vermont’s phenology. Spring comes earlier, and evidence abounds. As examples, lilacs have been leafing out around three days earlier, on average, each decade since tracking began in 1965, and the Sugar Maple season has shortened by about three days in the past 50 years, starting a week earlier and ending around ten days sooner. These earlier extended periods of warm weather cause some organisms to begin to emerge from hibernation or otherwise shift to spring activity, which can be fatal if winter conditions set in again.

Following the unseasonably warm weather this past April, I have been thinking a lot about phenological mismatches, which may also occur as a result of earlier springs caused by climate change. A phenological mismatch is when the life cycles of two (or more) species that rely on each other get out of sync. You may be thinking, “Well, if it gets warm and a flower opens, wouldn’t the increase in temperature also cause an obligate bee to emerge, along with the obligate bee parasite?” This certainly can be the case, if you are looking at species that use temperature as the cue to proceed from their winter activities into their spring activities. However, not all species use temperature as their cue. Others use photoperiod (length of the day), moisture, food availability, etc., or a combination of factors to trigger a response to transition from winter to spring activity. Even when different species rely on each other and have evolved to synchronize their life cycles to utilize each other during specific life stages, they still may use different cues or combinations of cues to spark spring activity.

Another factor that further complicates this issue is migration. For example, many species of migratory birds travel long distances. Since long-distance migrant birds travel so far from their breeding grounds to their overwinter habitats, they typically rely more heavily on changes in the photoperiod (rather than cues such as temperature change or snowmelt) to spark their migration. As a result, they have no way of knowing what the conditions of their breeding territory will be upon their return. If an unseasonably warm and early spring has caused the insects and other food sources a specific bird usually relies on upon their return, or a phenological mismatch between insects and the plant(s) they use occurred and caused mass mortality of those insects, the migrants could be in trouble.

Upon learning about phenological mismatches for the first time several years ago, I remember feeling rather helpless. Phenological mismatches are still relatively unstudied, and both adaptive abilities of different organisms and the extent of negative consequences from phenological mismatches remain a mystery. What could I do to help scientists gain a better understanding of these processes?

The answer is to document different species and their behaviors on platforms such as Vermont eBird, eButterfly, and iNaturalist. By simply uploading accurate observations and checklists (with correct date, time, and location information in addition to species, photographs, and notes), I am contributing data that helps researchers better understand how climate change is affecting our ecosystems. You can help too! Even contributions from your own backyard are valuable. When do the first Red-winged Blackbirds and warblers arrive each year? When do you begin to see insects emerging? When do tree buds open in spring? When do leaves fall in autumn? How about flowering times? Every bit of information helps.

The Blueberries and the Bees

By Spencer Hardy

Blueberry season in Vermont is a sweet one! With an abundance of pick-your-own farms and several wild species, it’s not to be missed. But why is mention of blueberry season in our Field Guide to May, when the first berries won’t be ripe until late June? Because for the bees, May is blueberry season. Blueberries are one of a few genera that have multiple specialist bees, and they are attractive to a wide range of generalists, including Bumble Bees.

While on the level of milk, syrup, and apples, blueberries are a major (and old) agricultural product in Vermont, and has been the focus of considerable research. This study from the University of Vermont found that native bees were much better pollinators of blueberries than the managed Honey Bee (Apis melifera). That same study also provided the Vermont Wild Bee survey with over 4,000 records of wild bees that has given us significant insight into the distribution of blueberry-associated bees in Chittenden County. Some blueberry specialists are relatively easy to find on blueberry farms, while others have not yet been found in Vermont. With a camera and a little luck, you could be the first to find one of these bees in VT!

Learn more about blueberry specialists here, and be sure to add observations of any bees you photograph to the Wild Bee Survey on iNaturalist.

Oh my, a Caddisfly!

By Julia Pupko

Caddisflies (Order Trichoptera) are small insects that resemble a moth or butterfly in their adult stage. However, most of this species’ life cycle will be spent as larvae, resembling small grubs with legs. Most Caddisfly larvae make little mobile homes (casings) that they use in a comparable way to the way that Hermit Crabs use shells. Other Caddisfly species build stationary casings that they venture out from to forage. Caddisfly casings can be made out of vegetation, sand, mud, twigs, or other materials, and are spun together using silk. A group of Caddisflies in the Limnephilidae family make their casings in an alternating perpendicular pattern, yielding the common name “Log-cabin Caddisflies.” These homes are built with specific materials based on species.

Caddisfly larvae and pupae live in surface water, including vernal pools. Three families of Caddisflies are common in vernal pools: Limnephilidae, Phryganeidae, and Polycentropodidae. One Log-cabin Caddisfly, Limnephilus indivisus, seems to preferentially live in vernal pools, and is a common species found in Vermont’s vernal pools. After vernal pools flood in the spring, eggs that were laid by certain Caddisfly adults the previous summer hatch and larvae begin to feed. Caddisfly larvae largely feed on detritus, assisting with nutrient cycling. However, some species eat living plants and/or animals as well. In early May, you should be able to find Caddisfly larvae moving around in vernal pools, often appearing to be moving clumps of detritus. After their growth period, the larvae will seal their casing and pupate inside, cutting through the casing once they have matured to emerge as adults.

By the end of May, adults of some species begin to emerge, either by chewing through their casing and swimming to the surface, or by crawling to land first then emerging. Others remain as larvae or pupae for longer. Many Caddisfly larvae, pupae, and adults will enter diapause during dry periods when the vernal pool has evaporated. The adults of Caddisfly species that utilize vernal pools can live up to three months, whereas Caddisfly adults that use other bodies of water typically only live up to one month. When conditions are right, adults in diapause emerge and lay their eggs at the bottom of the depression, so eggs can hatch when the vernal pool floods again. Some Caddisflies can live up to three years, primarily in their larval phase.

Keep an eye out for these neat critters in all aquatic habitats, especially in vernal pools, and upload your observations to iNaturalist!

What’s Eating Pete: Parasite Potions

By Pete Kerby-Miller

Lately, the Vermont bee watching season has bee-n off to the races in sandpits and backyard bare spots across the state. Sandpits, where abundant loose bare soil makes for easy burrowing, are a hotspot for bee activity. A lucky bee-watcher (or unlucky bee) might spot a brilliantly colored Tricrania sanguinipennis among the emerging ground nesting bees.Their bright vermillion color is a warning to would-be predators, but it is their tiny, worm-like larvae that bees had better hope to avoid.

Adults of the blister beetle T. sanguinipennis are flightless and don’t appear to eat. They emerge in spring and quickly mate and lay eggs very close to the tunnel from which they emerged. Come May, those eggs hatch, and vice-mandibled larvae wander about seeking a hairy bee to clamp on to. Excellent natural history observations from a century ago details their journey. These beetles overwinter underground, using their clamp-like jaws to hitch a ride on a female bee before it burrows and builds subterranean nest chambers. You might find these hitchhikers on male bees as well, but their attachment pattern is different: on males, T. sanguinipennis larvae might be anywhere on the abdomen, but on females, larvae are almost always found on top. The larvae seem to clamp on to whatever bee they encounter first, then, if they happen to be riding a male, transfer to the back of a female when the two bees mate.

While the beetle larvae seem able to determine the sex of their bee-mobile, they would be well served to notice the species as well. Both Andrena and Colletes frequent sandy soil, and the fate of larvae attached to different species is vastly different. Members of both genera dig tunnels and build subterranean nest cavities that are waterproofed and filled with nectar and pollen and a single bee egg. The female bee seals the cavity behind her, leaving the egg to hatch and spend a warm winter below ground eating its stored food. T. sanguinipennis crash this party by detaching from the female bee while she’s building the nest chamber, then eating first the egg, and then the nectar and pollen. With Colletes, the beetles might be pretty successful. Andrena perplexa, though, has evolved a behavior to thwart the beetle kleptoparasites. Whereas Colletes might lay their eggs against a wall of the nesting chamber, Andrena perplexa carefully forms a ball of pollen in the middle of the chamber, then lays her egg directly on top of that ball before flooding the chamber partway with nectar. Any T. sanguinipennis larvae that snuck in with her cannot reach the egg without drowning in a pool of nectar. Colletes also fill nest chambers with nectar–it’s good baby bee food after all–but their tendency to lay their eggs against the walls gives T. sanguinipennis the chance to have one large, dry meal. That’s all it takes to fuel their first molt. When T. sanguinipennis first hatch, they are soft-bodied and grublike, but after their first molt, they develop into a boat-shaped, hard-shelled form with breathing holes moved to their top-side–perfect for floating in a nutritious lake of nectar. They’ll feast on their stolen cache of food for another 11 months before emerging in spring as adults, along with any bees that survived in neighboring nest chambers. Unless, of course, multiple beetle larvae jettisoned themselves in the same nest. If that was the case, there’s a deadly showdown in the dark and sticky nest chamber. Town’s not big enough for two kleptoparasites.

Horrifying subterranean siblicide aside, I reckon those of y’all who speak a little Latin might have had a giggle at the species epithet of this particular blister beetle. It’s a reference to a long and dangerous history of blister beetles being used as an aphrodisiac. When Thomas Say described T. sanguinipennis in 1823, it was within living memory of an infamous French Marquis being sentenced to death for poisoning attendees of a… party… with sweets laced with beetle extract. Blister beetles are so named because they cover their eggs with a substance that quickly induces terrible painful blisters. How then did they become recognized as an aphrodisiac in antiquity? Well, there are likely millennia-dead naturalists to thank for that. Prior to mating, a male blister beetle exudes a waxy ball that he presents to a female as a nuptial gift. If she is satisfied, they will mate. Perhaps careful observation of this behavior lead to the first association of blister beetle wax with sex. After mating, though, the female will cover her eggs with that exudate as a painful, burning chemical defense. The amorous among us should remember that bright colors are often a sign of warning: these beetles are best admired from a distance.

Be on the Lookout for Lady Beetles

By Julia Pupko

At some point in history, a community of European farmers had an issue—a boom of aphids were absolutely destroying their crops. The farmers, presumably rather distraught, prayed to the Virgin Mary for the protection of their crops. When a swarm of ladybugs arrived, they named the beetles “beetle of our Lady,” which was then shortened to “lady beetle,” then finally shortened to ladybird. Ladybug is the American derivative commonly used in Vermont today.

There are many more common names and name origin stories for the Coccinellidae family (ladybugs) than the aforementioned European name and story. This is because ladybug species are found across the globe, are rather endearing in appearance, and are generally viewed positively across different cultures—most lady beetle species effectively prey on aphids, protecting crops and ecosystems from damaging populations of small, soft-bodied insects.

Like the high number of common names, there are a high number of ladybug species. In North America, we have over 475 species, and in Vermont we have 42 that have been recorded thus far (35 native, seven introduced). These lady beetles can be found across all terrestrial habitats in Vermont, from valley cornfields to the top of Mt. Mansfield. Between April and May, lady beetles begin to emerge from their hibernation spots. Most lady beetles overwinter as adults in aggregations (groups) in leaf litter, under logs, and sometimes in the bark of standing live and dead trees. When they emerge from their overwintering sites, many species will breed and then migrate to their summer sites or disperse into the immediate area of the overwintering site.

Once they have found a suitable habitat, the adults will feed, either start or continue to breed, and lay their eggs. Eggs are typically laid on vegetation or tree bark (depending on species) with high prey loads. Eggs will typically hatch in a few days to a week, and larvae emerge, feeding on unhatched eggs, younger lady beetle larvae, and small soft-bodied insects. After going through four growth phases (instars) as larva, lady beetles pupate and emerge as adults. These phases (larva->pupa->adult) can take a few weeks to months, depending on the species and environmental factors. Some species have multiple generations in a year, while others only have one generation (univoltine).

Lady beetles effectively control aphid and other such insect populations as larvae and adults. Many native species specialize as predators for a few taxa or species, actively hunting these insects and synchronizing their life cycles with their prey of choice. Unfortunately, lady beetles are in decline across North America. This is thought to be caused by a combination of different factors, including land use change and the introduction of non-native species such as Asian Lady Beetles, a widely-recognized lady beetle species that commonly invades homes in winter across North America.

Vermont’s native lady beetle species seem to be following national trends—as of now, there are twelve native lady beetle species that have not been seen since the 1976 Vermont lady beetle checklist was published. Other native species found in Vermont, such as the Convergent Lady Beetle (Hippodamia convergens) seem to be in sharp decline. As a response to these alarming trends and lack of current data, VCE’s Vermont Atlas of Life launched the Vermont Lady Beetle Atlas.

With the help of our community naturalists (this could be you!) we hope to complete an atlas of the lady beetles of Vermont over the next four years. Lady beetles can be found in fields and on the trunks and branches of trees and bushes as they emerge from overwintering sites.  If you see a lady beetle, snap a few photos and add your observations to the Vermont Lady Beetle Atlas on iNaturalist. Check out the Vermont Lady Beetle Atlas website to learn more and get all the details about how you can participate!

Wandering Warblers

By Julia Pupko

In Vermont, we have resident birds (that live here year round), irruptive species (that migrate south to Vermont in winter), and birds that migrate south during winter then return to (or pass through) Vermont to breed in the spring. Our feathered friends that depart from Vermont during the cold months can be broken into two broad groups: facultative and obligate migrants. Facultative migrants are typically short-distance migrants, migrating just far enough south to avoid the brunt of winter. They typically use some combination of cues, such as temperature or weather, to decide when to migrate north again. Obligate migrants, on the other hand, are the longer-distance migrants that fly to the Caribbean or Central and South America for the winter. These species usually rely on changing photoperiod to cue their return north; changes in the weather do not affect migration times beyond potentially halting migration for a day or two if the local weather is unnavigable. That said, some species do not fall nicely into the box of facultative or obligate.

Early May is the time when many of our obligate migrants arrive, including many warbler species. While some species, such as Palm, Pine, and Yellow-rumped Warblers are already here, keep an eye out for incoming Black-and-White, Blackpoll, Blackburnian, and Black-throated Green Warblers, just to name a few. A great part of spring migration is that you can find birds, such as warbler species, in places that you will not find them once they begin breeding. These areas could be the shrubs in your backyard or a small riparian zone near your house. What a thrill it is to spy these jewels of spring as they arrive!