{"id":9724,"date":"2018-09-25T09:01:10","date_gmt":"2018-09-25T14:01:10","guid":{"rendered":"https:\/\/uwm.edu\/field-station\/?p=9724"},"modified":"2024-12-26T14:33:33","modified_gmt":"2024-12-26T20:33:33","slug":"maple-spanworm","status":"publish","type":"post","link":"https:\/\/uwm.edu\/field-station\/bug-of-the-week\/maple-spanworm\/","title":{"rendered":"Maple Spanworm"},"content":{"rendered":"\n

Howdy, BugFans,<\/p>\n\n\n\n

Isn\u2019t this moth exquisite! It\u2019s one of several moths in the family Geometridae<\/em> that go by the same name – Maple Spanworm<\/strong> (more about that in a future episode). And it\u2019s one of several \u201cnew bugs\u201d that the BugLady saw for the first time this year. Here\u2019s a glamor shot of one.<\/a><\/p>\n\n\n\n

\"Maple<\/a><\/figure>\n\n\n\n

Anyway, Geometrids – Geometer moths – are, as long-time BugFans know, named for the way their caterpillars walk. Geometrid means \u201cearth measurer,\u201d and the caterpillars are fondly nicknamed \u201cinchworms,\u201d \u201cloopers,\u201d and \u201cspanworms\u201d because of their gait. Lepidopteran caterpillars have three \u201ctrue\u201d legs in front, on their thorax (caterpillars are divided into three sections, just like their elders). The rest of that long body is supported by prolegs<\/em> – fleshy, hydraulically-powered stubs tipped with hooks (crochets) for gripping the substrate.<\/a> A full complement of prolegs is five pairs, the hindermost being a pair of anal prolegs at the tip of the abdomen. Geometer caterpillars are missing two or three pairs of prolegs between the true legs and the anal prolegs, and the result is that instead of uniform undulation, the inchworm reaches its front end forward and then arches to pull the rear end up to it. For a full explanation of prolegs and some super photos, check out this post from The Caterpillar Lab.<\/a><\/p>\n\n\n\n

Several sources said that Maple spanworms (Ennomos magnaria) are a sign that the days of summer are numbered (the BugLady found two of them at the start of September). They\u2019re found around woodlots and swamps across southern Canada and the northern half of the US<\/a>. Adults are nocturnal, and may rest on the sides of buildings by day.<\/p>\n\n\n\n

\"Maple<\/a><\/figure>\n\n\n\n

With a wingspan of 1 \u00be\u201d to 2 \u00bc\u201d they\u2019re decent-sized moths. What cool wings! Their unevenly-scalloped edges explain this moth\u2019s other common names – Notch-wing moth and Notched-wing geometer. What a dynamite color! And what a posture – like one of those figure-skating moves where the skater holds her foot in back of her head! There are plenty of moths that are leaf mimics, but this one takes it to another level by imitating dry, curled leaves.<\/p>\n\n\n\n

The caterpillars take twig mimicry to a new level, too. Swellings on the caterpillar look like bits of twig anatomy \u2013 leaf scars, bud scars, and lenticels: https:\/\/bugguide.net\/node\/view\/1484763\/bgimage<\/a>, https:\/\/bugguide.net\/node\/view\/132141\/bgimage<\/a>, https:\/\/bugguide.net\/node\/view\/818291\/bgimage<\/a>, https:\/\/bugguide.net\/node\/view\/291625\/bgimage<\/a>.<\/p>\n\n\n\n

David James, et al, in The Book of Caterpillars: A Life-Size Guide to Six Hundred Species from around the World<\/em>, tell us that:<\/p>\n\n\n\n

\n

\u201cMaple spanworm caterpillars hatch from overwintering eggs laid in rows on their host plant. Both edible and abundant, the caterpillars have evolved a remarkable ability to camouflage themselves. So as not to create a searchable pattern for predators, the green, brown, or gray coloring of their body varies, and they also blend perfectly with their host plant by assuming a stiff, twiglike position during the day.\u201d<\/p>\n<\/blockquote>\n\n\n\n

The BugLady assumes that \u201cedible,\u201d here, means edible by the usual caterpillar-eating suspects, not in an entomophagy context. Jim Sogaard, in Moths and Caterpillars of the North Woods, says that the caterpillars are \u201csuperb examples of \u2018vegetable disguise.\u2019\u201d Despite their camouflage, they are found and eaten by birds and by other insects and are parasitized by wasps.<\/p>\n\n\n\n

\"Maple<\/a><\/figure>\n\n\n\n

One source pointed out that the name \u201cMaple spanworm\u201d is misleading because it implies that the caterpillar is a specialist feeder on maples. In truth, its menu is so varied that its host plants include much of what grows in Wisconsin\u2019s deciduous woods and wetlands – alder, ash, basswood, elm, hickory, birch, beech, poplar, willow, holly, and oak \u2013 and maple.<\/p>\n\n\n\n

In fall, females lay eggs on a host plant, and there the eggs overwinter. They hatch in spring and the caterpillars feed, but instead of descending and pupating on\/in the ground, they spin a silken cocoon in the leaves and pupate there, emerging as adults in mid-to-late summer.<\/p>\n\n\n\n

\"Maple<\/a><\/figure>\n\n\n\n

Of the caterpillar, David Wagner says in his book Caterpillars of Eastern North America, that \u201cBy flashlight, these enormous loopers are readily discovered \u2013 look for them at the end of a shoot.\u201d<\/p>\n\n\n\n

On a different topic, it\u2019s Woolly Bear Caterpillar Time! To find out what they\u2019re telling us about the coming winter, see this previous BOTW post.<\/a><\/p>\n\n\n\n

The BugLady<\/em><\/p>\n","protected":false},"excerpt":{"rendered":"

Isn\u2019t this moth exquisite! It\u2019s one of several moths in the family Geometridae that go by the same name – Maple Spanworm (more about that in a future episode). 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