A Mystery Bug

Brochymena quadripustulata
Brochymena quadripustulata

 

It’s winter here and the nighttime lows have been very cold. Daytime highs aren’t much better. The first two weeks of January were mild but very suddenly our temperatures went from 35 above to 24 below. So, as I often do on cold winter nights, I go through my photo files.

There are a number of photos in my files of insects and spiders that I have taken over the years. Some have been identified and others not. Recently, I was going over some old photos from 2007 and found one of a bug (Order Hemiptera, the true bugs) on an aspen leaf. This bug, one of my mystery insects, has puzzled me for years. What species is it? I went back to the Bug Guide web site and to look at bug photos. There are a lot of species of bugs and many resemble this one. It is gray-brown with 4 reddish spots, rough edged shoulders, and a scalloped black and red fringe coming from under the wings. By its shape I guessed it might be a stinkbug or shield bug. The scalloped red and black fringe reminded of an assassin bug although as it turns out the two are not closely related.

I began my search in the stink bug family Pentatomidae which has five subfamilies: Asopinae, Discocephalinae, Edessinae, Pentatominae, and Podopinae. Starting with the subfamily Asopinae I found a few suspects such as Apateticus lineolatus and Apoecilus bracteatus. But there were important differences such as no reddish spots and pointed or smooth-edged shoulders rather than jagged. Also, Apateticus lineolatus lives in the southern US and so its presence in Minnesota would be an anomaly to say the least.

It was a long trek through hundreds of photos and pages of descriptions. Eventually I arrived at the subfamily Pentatominae. The Subfamily Pentatominae contains 14 tribes and the tribes include 43 genera. More browsing into the late hours of the night ensued. It was in the subfamily Pentatominae that I found images of bugs that looked very similar to mine. The bug was in the tribe Halyini, genus Brochymena and is known as Brochymena quadripustulata, the rough-shouldered stinkbug. Also, importantly, this species lives in the northern US and Canada.

Description
The rough-shouldered stinkbug is so named for the rounded and jagged-toothed shoulder (humeral angles) of its thoracic segment. The body (8 mm long by 6 mm wide in males, 17 mm long by 9 mm wide in females) is an elongate oval, brown in color with numerous irregularly spaced small black sunken (punctate) dots with yellow or yellow-white markings in between. On the thoracic plate (pronitum) and shield (scutellum) between the wing covers are four orange or red-orange lumps (calluses). The edge of the abdomen is scalloped and marked with alternating stripes of red and black. The fuzzy legs are marked irregularly with alternating spots and patches of yellow and black giving this bug another name “banded stinkbug”.

Life Cycle
Because it is not a serious pest of cultivated plants the rough-shouldered stinkbug is not well-studied but there is enough information available to make some statements about its life cycle. Rough-shouldered stinkbug over winters as an adult under leaf litter and loose bark. In the spring after mating the female lays eggs which incubate for about 10 days before hatching. Development form newly hatched nymph to mature adult takes about three months.

Both nymphs and adults feed on a wide variety of plant species but also on caterpillars. Otto Lugger (1900, as B. annulata) recorded this species as a pest of apple trees in Minnesota but he also notes an earlier observation of it feeding on caterpillars. Several other authors in the early part of the 20th century also noted that rough-shouldered stinkbugs feed on insect larvae.

Taxonomy
Class Insecta: Insects
Order Hemiptera: True Bugs, Cicadas, Hoppers, Aphids and Allies
Suborder Heteroptera: True Bugs
Infraorder: Pentatomomorpha
Superfamily: Pentatomoidea
Family Pentatomidae: Stink Bugs
Subfamily: Pentatominae
Tribe: Halyini
Genus/Species: Brochymena quadripustulata

Distribution
Rough-shouldered stinkbug is found from southern Canada and across most of the US (including Alaska) and northern Mexico. It is considered to be the most common member of its genus.

References consulted

Cuda, J. P. and McPherson, J. E. (1976). Life History and Laboratory Rearing of Brochymena quadripustulata with Descriptions of Immature Stages and Additional Notes on Brochymena arborea (Hemiptera: Pentatomidae). Annals of the entomological Society of America. 69(5): 977-983.

Lugger, O. (1900). Bugs (Hemiptera) injurious to our cultivated plants. Minnesota Agricultural Experiment Station Bulletin 69: 1–259.

McPherson, J. E. (1982).The Pentatomoidea (Hemiptera) of Northeastern North America. Southern Illinois University Press.

Paiero, S. M.; Marshall, S. A.; McPherson, J. E.; and Ma, M. S. (2013). Stink bugs (Pentatomidae) and parent bugs (Acanthosomatidae) of Ontario and adjacent areas: A key to species and a review of the fauna. Canadian Journal of Arthropod Identification No. 24.

Stoner, D. (1920). The Scutelleroidea of Iowa. University of Iowa Studies in Natural History. Vol. 8, No. 4:1-155.

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