Category: insect

Unicorn caterpillar (Schizura unicornis), Newa…

Unicorn caterpillar (Schizura unicornis), Newark DE. June 2018 (2nd pic from July). 

The unicorn caterpillar aptly earns its name from the horn-like projection from its first abdominal segment. Its patterning of a leafy-green thorax turning to brown like dying leaves or even a stem helps the caterpillar fade into the background of its host plant. These caterpillars are generalist feeders that consume leaves from many trees and shrubs, including apple, beech, birch, cherry, dogwood, hickory, maple, oak, and willow. This caterpillar was raised on hop hornbeam (Ostrya virginiana)

At least two generations in the Mid-Atlantic, with caterpillars by late spring and again by late summer. Caterpillars overwinter as pupae. 

Eastern tiger swallowtail caterpillar (Papilio…

Eastern tiger swallowtail caterpillar (Papilio glaucus), Newark DE. June 2018.

An iconic caterpillar in the eastern US, the tiger swallowtail sits on the upper side of leaves during the day, blending into the green background of its host plants. At younger molts, however, the caterpillar is mottled brown and white, resembling a bird dropping. Both strategies protect the swallowtail from predators. 

It is theorized that the swallowtails here in North America have a tropical ancestry, and their rainforest ancestors defended themselves from being fed on by birds by mimicking the appearance and behavior of snakes. There is evidence to support this in the tiger swallowtail, who has eyespots on its thorax that resemble a snake’s eyes. If startled, caterpillars even have an forked-like organ (called an osmenterium) which inflates from just above the head and emits a foul-smelling chemical, like a snake spitting poison. 

(Caterpillar displaying osmenterium, photo credit to Dougeee via Flickr)



Monarch butterfly egg (Danaus plexippus), Elkton, MD. August 2015

At this point in the Mid-Atlantic, the summer monarch populations are looking seeking out milkweeds to lay their eggs and start one more generation before the migratory monarchs come into the fold.

Eggs are laid singly on a milkweed leaf, and can be difficult to spot due to their size (except when you are following a female monarch!). Monarchs tend to lay only one egg per milkweed plant, making their life cycle all the more vulnerable. 

Swamp milkweed beetle (Labidomera clivicollis …

Swamp milkweed beetle (Labidomera clivicollis ), Newark DE, June 2018.

Like the monarch butterfly, the swamp milkweed beetle bears an orange-and-black patterning, characteristic of many species that feed on milkweed plants. This coloring signals to predators that the beetle is distasteful and toxic, and those predators who learn from this mistake learn to also avoid other insects bearing the same appearance as the beetle. 

Like monarch caterpillars, these beetles need to avoid the milky latex sap that is released by the leaf veins, as it would glue their mouthparts together and prevent them from feeding. To do so, the beetles (both immatures and adults) cut the major veins before feeding on tissue further away, keeping the latex from reaching where they feed. 

One generation a year. Adults common throughout summer. Larvae pupate on the ground and adults overwinter in leaf litter. 

This is from an earlier post, but in light of …

This is from an earlier post, but in light of people asking what to plant for monarch butterflies, I wanted to include this on MONARCH MONDAY. 

The above picture (courtesy of Home Depot) is tropical milkweed or bloodflower (

Asclepias curassavica). This nonnative plant is commercially available at many garden stores, and stores will inform you it is a benefit to pollinators, wildlife, and the monarch butterfly. 


Native milkweeds lose their leaves in the fall, which signals to monarchs to develop into adults and contribute to signaling the migration. Tropical milkweed is an evergreen, so many monarchs die from the cold before they can migrate. Furthermore, Tropical milkweed accumulates pathogens for monarchs migrating south, which is contributing to population declines during migrations.

Please do not plant tropical milkweed in your gardens. Consider instead purchasing native milkweed plants that are local to your area, like common milkweed, butterfly milkweed, and swamp milkweed (for those in the Mid-Atlantic). 

(Monarch butterfly on butterfly milkweed, Fishers Island NY August 2015

(Monarch caterpillar on common milkweed, Bear DE, June 2016)

Cecropia moth (Hyalophora cecropia), Newark DE…

Cecropia moth (Hyalophora cecropia), Newark DE. June 2018.

My caterpillars emerged from their cocoons two weeks ago, and after some successful matings with wild individuals, they were released. Here’s to another generation. 

 Cecropia moths are the largest member of the silkmoth family in eastern North America. They can feed on a variety of hosts: apples, ash, cherry, lilac, poplar, willow, but in the Mid-Atlantic, they seem to show preference for ash trees and cherry. One generation, caterpillars through June to August, overwinter as pupae and adults emerge late May.

Unfortunately, Cecropia moths have been in decline for some time now due to nonnative parasitic flies (Tachinidae). The flies lay their eggs only when the moths are caterpillars, so rearing the larvae in cages greatly increases their survival rate. This was what first got me interested in rearing caterpillars, and helped foster my interest in the field of entomology.  

Due to computer troubles, I was unable to do a…

Due to computer troubles, I was unable to do a MONARCH MONDAY earlier this week. So I’ll post it now. 

Monarch butterfly caterpillar (Danaus plexippus), Newark DE. June 2018. 

Although monarch butterfly caterpillars have evolved to recognize milkweeds as food and overcome their toxic properties, their host plant still poses some danger. Milkweeds, as they are aptly named, produce a milky white latex in the vascular tissues that can glue together the mouthparts of insects that feed on the leaves, a situation that quickly leads to death for many insects. 

Monarchs get around this by “flagging”–a process by which they sever the main stem of the leaf and prevent the latex from reaching the rest of the leaf tissue. This causes the leaf to hang in a characteristic 90 degree angle as the caterpillar consumes it. If you see a flagged milkweed leaf, you probably have a monarch nearby. 

Helmeted squash bug (Euthochtha galeator), Ste…

Helmeted squash bug (Euthochtha galeator), Stephenville TX. June 2018. 

Had an opportunity to briefly visit a pollinator garden in Texas; ironically I ended up taking photos of non-pollinating insects. 

Squash bugs earn their name, somewhat unfortunately, for being pests on vegetable plants like squash, and their feeding can misshapen the fruit.The helmeted squash bug feeds on vegetable and fruit plants, but can be found feeding on wildflowers as well. They are related to stink bugs and possess scent glands in their thorax that release a strong odor when handled.  

In Texas, squash bugs can be found year-round. In the Mid-Atlantic, they have at least one generation a year, and adults can sometimes overwinter in homes. 

Fall webworm (Hyphantria cunea), Willistown PA…

Fall webworm (Hyphantria cunea), Willistown PA, June 2018

Despite their name, fall webworms can be found as caterpillars as early as June (such as these early instars, feeding on honeysuckle). The name largely comes from the fact that the protective webbing the caterpillars spin around themselves are obvious in the fall, and that mature caterpillars leave their webs in the fall and appear on other plants before pupating. 

Caterpillars have been recorded on feeding over 120 separate species of plants, although they are mostly found feeding on woody plant species. Although they can defoliate trees when at large numbers, they cause little economic or ecological damage (by the time the damage occurs, it is usually at the end of the growing season). 

At least one generation a year in the Mid-Atlantic, with caterpillars from June through September. 

It’s that time of year again for the return of…

It’s that time of year again for the return of MONARCH MONDAY! Every Monday for the summer months, I’ll be sharing pictures and information on one of the most iconic species of insect in the Americas. 

Monarch butterfly (Danaus plexippus), Fishers Island, NY. July 2017.

Although bees are credited as being important pollinators for plants, many other species of insects serve that ecological role, including the monarch butterfly. As adults, monarch butterflies may feed on the nectar of a variety of flowering plants during the summer months. and especially during the fall migration. However, they will quickly take to milkweed flowers if available. 

In the image above, this monarch female is taking nectar from a butterfly weed (Asclepias tuberosa), a species of milkweed that establishes well in the northeastern US and is a common sight in butterfly gardens.