With winter fast upon us and most deciduous trees and shrubs already naked, my sweet autumn clematis, Clematis terniflora, still shines like a beacon of green as it engulfs a lamppost in the front yard. After rewarding me with fragrant blossoms for much of the fall, this non-native invader is hosting an entire food web of alien insects. Let’s start with the herbivores, a flock of peach-clematis aphids. During spring and summer, through Thanksgiving, and, in this era of climate change perhaps all winter, my clematis will be home to peach-clematis aphids. Several species of clematis and peaches serve as food for this now cosmopolitan vagabond. Beneath each leaf, scores to hundreds of aphids suck nutritious phloem sap. Over the past several months and in years past, the aphid horde is so abundant that clematis leaves drip with honeydew, which in turn serves as a substrate for the growth of sooty mold. This type of non-pathogenic fungus, akin to one produced by boogie woogie aphids and woolly alder aphids we met in previous episodes, blackens leaves and may interfere with photosynthesis.
The saga of the peach-clematis aphids began earlier this year in the spring when winged aphids migrated from a tree in the peach clan (Prunus) to the clematis vine clinging to my lamppost. During the warm months of summer and fall, surviving females begin reproducing without assistance of males. This form of reproduction, called parthenogenesis, produces only females, thus enabling aphid populations to increase rapidly. As I examined my colony of aphids recently, I noticed several winged adults mixed with the parthenogenetic females. In cold regions like Maryland, when temperatures turn chilly, male and female winged adults are produced and leave the clematis, returning to Prunus to mate and lay eggs that will spend the winter on the bark of the tree. Sexual reproduction in the fall produces eggs, the overwintering stage of the aphids. In spring, the eggs hatch and the complex life cycle of the aphid resumes.
Another fact of life contributing to explosive population growth of aphids is their ability to skip the usual insect-like business of laying eggs. Many species of aphids dispense with the egg stage and, like humans, give live birth to their babes. This blessed event takes only a few minutes but appears to be fraught with significant drama. Birthing aphids do lots of posturing and pushing. Fortunately, aphids have sucking mouthparts and loud vocalizations such as those accompanying human births are conspicuously absent. To further accelerate the process of filling the world with their kind, female aphids carry embryos of their grandchildren within their bodies even before they are born (i.e. their daughters are born already pregnant). This further compresses the generation time for aphids and is part of the reason aphid populations rapidly grow from a few to thousands.
With Thanksgiving in the rear view mirror and the rest of Holiday Season just around the corner, peach-clematis aphids are still living it up on sweet autumn clematis. On a leaf blade a mother is surrounded by her daughters, and on a petiole aphids suck sap from phloem. Just for fun, watch the live birth of an aphid (five times actual speed). Note that aphid births are breech. At the end of the clip, is that older sister coming to see how mom and little sister are doing? Dance of the Sugar Plum Fairy by Kevin MacLeod is licensed under a Creative Commons Attribution 4.0 license, https://incompetech.com/music/royalty-free/index.html?isrc=USUAN1100270. Artist: http://incompetech.com/
Just as my clematis serves as a feast for aphids, so too will the aphids and their honeydew serve as dinner for guests higher up the food chain. Roaming around my clematis, multicolored Asian lady beetle larvae snack on aphids. Their alligator-like larvae patrol leaves and stems searching for tasty aphids. Without much stealth or finesse, larvae capture aphids in their jaws and proceeded to munch their hapless prey. Small aphids disappear in just a minute or two, but large, plump aphids required several minutes to eat. A single larva of the multicolored Asian lady beetle may devour 1,200 aphids during the course of development. Adults of this species can also kill hundreds of aphids during their lifetime. This capacity to eat so many aphids makes the multicolored Asian lady beetle one of the most effective biological control agents in our gardens.
In this microcosmic food web, clematis is food for the peach-clematis aphid, and aphids will become food for both adult and larval lady beetles. A yellowjacket laps up carbohydrate rich honeydew produced by the aphids. This rich source of carbohydrates may help yellowjackets fatten up to survive a wicked winter. Dance of the Sugar Plum Fairy by Kevin MacLeod is licensed under a Creative Commons Attribution 4.0 license: https://creativecommons.org/licenses/by/4.0/, Source: http://incompetech.com/music/royalty-free/index.html?isrc=USUAN1100270, Artist: http://incompetech.com/
And during this season of Holiday feasts, what banquet would be complete without dessert? With gobs of sweet honeydew on leaves, dozens of hungry yellowjackets recently visited the clematis to lap up a carbohydrate rich meal to fatten up for their winter rest. So, in this festive season, while we devour turkey and savor pumpkin pie, reflect on the happy feasts underway on greenery like an autumn clematis where aphids dine and serve dinner to other creatures higher up the food web.
Bug of the Week thanks Roger Blackman and his amazing website, Aphids on the World’s Plants: An online identification and information guide at http://www.aphidsonworldsplants.info/ which served as a reference for this episode. The fact-filled leaflet “Multicolored Asian Lady Beetle” by Janet Knodel, E. Richard Hoebeke, and Carolyn Klass, Dept. of Entomology, Cornell University provided great information on the ladybeetle. Many thanks to Dr. Gary Miller of USDA’s Systematic Entomology Laboratory for his help in identifying the tiny star of this episode.