May has started off with a string of beautiful, sunny days, and more new birds have been announcing their arrival each day. On the 1st it was the blue-headed vireo; on the 2nd a ruby-throated hummingbird joined the myriad bees, wasps, and flies buzzing around the plum trees that had just burst into bloom, while a blue-gray gnatcatcher wheezed from the trees around the edges of the yard; yesterday the morning started off with the song of a black-throated green warbler, followed before long by ovenbird, common yellowthroat, black-and-white warbler, chestnut-sided warbler, gray catbird, eastern towhee, and barn swallow; and this morning a rose-breasted grosbeak and Baltimore oriole have already joined the chorus (those two always seem to arrive together).
Amid all these arrivals, the season’s eighth leafminer species has made its presence known in my yard: plantain flea beetle (Chrysomelidae: Dibolia borealis). As with the Chrysoesthia sexguttella that are still swarming inside the hoop house, it is the adults rather than the leaf-mining larvae that are now appearing. Unlike those moths, though, these beetles are not newly emerging from pupae; they have been hunkered down as adults since early last summer. I woke up this morning thinking how odd it is that the tiny beetles that are now nibbling the plantain leaves in the lawn were already adults last July when we bought the little fuzzy day-old chicks that are now full-grown hens, laying enough eggs every day to feed me and Julia as well as several neighbors.
After nibbling on plantain leaves for a few weeks, the beetles will begin laying eggs on them, and in June the trails of the larvae mining inside them will be obvious.
When full-grown, the bright yellow-orange larvae will exit their mines and burrow into the ground to pupate, emerging as adults in July.
The new adults may nibble on plantain leaves for a little while, but soon they will go into hiding until the following spring.
Dibolia borealis is among that small minority of native North American species that have become more common and widespread since Europeans arrived here. Over five hundred years ago, they would have fed only on the native Plantago species, which are spotty in their distribution. But they have expanded their diet to include the European P. major, which is now ubiquitous in lawns and other disturbed areas. In Helen Reed’s study of this species at Cornell University nearly a century ago*, she stated that both adults and larvae of D. borealis appear to feed exclusively on P. major, although she found that captive larvae would mine into leaves of another European import, P. lanceolata, when given no other choice. I did find a single mine on P. lanceolata in my yard three years ago, but it is clear that this is not a preferred host.
Meanwhile I, adaptable creature that I am, have so far eaten 35 different plant species in my yard this spring. The latest additions:
31. Tall blue lettuce (Asteraceae: Lactuca biennis) – leaves
32. Carrot / Queen Anne’s lace (Apiaceae: Daucus carota) – roots
33. Virginia waterleaf (Hydrophyllaceae: Hydrophyllum virginianum) – leaves
34. Tower mustard (Brassicaceae: Turritis glabra) – leaves, flowers
35. Shepherd’s purse (Brassicaceae: Capsella bursa-pastoris) – leaves, flowers, fruits
Asparagus, you’re next!
* Reed, Helen. 1927. Some observations on the leaf-mining flea-beetle Dibolia borealis Chevrolat. Annals of the Entomological Society of America 20(4): 540–549.