Differentiating the Mature Larvae of Adoneta spinuloides (Purple-crested Slug) and Adoneta bicaudata (Long-horned Slug)

The mature larva of A. spinuloides (Purple-crested Slug)is an extremely colorful species of slug caterpillar, existing commonly throughout eastern North America, its current range. Although this larva is commonly mistaken as the only caterpillar of its kind in eastern North America, a second Adoneta, A. bicaudata, closely resembles A. spinuloides, occurring much less commonly. Because of its obscurity, it is a poorly known species and easily mistaken as A. spinuloides. Listed below are the best characters of distinction for the two:

(Please note that only mature larvae apply to these characters).

  1. The purple dorsal coloration of A. spinuloides exists as several blobs not related to each other in size, while the purple coloration in A. bicaudata is present as several diamond-shapes relatively similar to each other in size.
  2. The curved, posterior scoli of A. bicaudata are 2-3x longer than those of A. spinuloides, which are gumdrop-like.

Check out the links below to compare the two using the listed characteristics:
https://www.inaturalist.org/observations/100969319 (Adoneta spinuloides)
https://www.inaturalist.org/observations/95589208 (Adoneta bicaudata)

Posted on November 20, 2021 03:14 AM by tcooley tcooley


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