ID Tip: Seven-spotted or Nine-spotted Lady Beetle?

Today's identification tip involves separating two nearly identical lady beetles: the Seven-spotted Lady Beetle, Coccinella septempuncta, introduced from Europe, and the native Nine-spotted Lady Beetle, Coccinella novemnotata. There is widespread speculation that the exotic Seven-spotted ("C-7") has displaced the native Nine-spotted ("C-9"), and indeed the latter species has become noticeably scarce over most of its former range, especially in the eastern U.S., over the last 35 years or so. That is why it is critical to be able to identify C-9 and report sightings to the Lost Ladybug Project.

Typical specimen of Seven-spotted Lady Beetle ("C-7")

Physical Features

The most dependable, though subtle, difference between these two species is found on the front edge of the pronotum (top of thorax). In the Seven-spotted Lady Beetle, only the corners, or "lapels" if you will, are white. The remainder of the pronotum is black. In the Nine-spotted Lady Beetle, the entire pronotal "collar" is white, so the front edge of the pronotum is white, from corner to corner.

Specimen of the Nine-spotted Lady Beetle ("C-9")

Meanwhile, the wing cover (elytron) of the Nine-spotted Lady beetle does bear an extra black spot, located near the "shoulder." This spot can, however, be vague or even obsolete. The markings on the pronotum are much more consistent.

The Nine-spotted Lady Beetle is usually slightly smaller than the Seven-spotted, and is more often a creamy orange in contrast to the brighter orange, or red, of C-7. Both species are polished (shiny) in texture, and highly convex or nearly hemispherical in shape.

Heavier spots on this C-9

Behavior

There is little difference in behavior between these two species. Both are predators of aphids and can be found on plants hosting aphid colonies.

Another example of the Nine-spotted Lady Beetle

Habitat

Habitat is not a good way to distinguish these two lady beetles, either. Both occur in a variety of ecosystems, from vacant lots, yards, gardens, parks, and forest edges to orchards and agricultural fields.

Complicating Factors

A nearly spotless form of the Multicolored Asian Lady Beetle

There are a surprising number of nearly identical lady beetle species, and simply counting the spots is a very unreliable way of making an identification. There is extreme variability in many species, especially the abundant Multicolored Asian Lady Beetle, Harmonia axyridis, which is yet another non-native ladybug. Not only does the number of spots on the elytra vary, but so do the markings on the pronotum. This species needs to be ruled out before you try and conclude whether your specimen is a C-7 or C-9.

Transverse Lady Beetle

Here in the western U.S., we also have the Transverse Lady Beetle, Coccinella transversoguttata, which resembles C-7 except that the spots on the elytra near the pronotum are connected to form a horizontal black bar between the "shoulders." The Transverse Lady Beetle also appears to be suffering in the wake of C-7's arrival.

Quiz Photo: Which species is this one?

Please keep a lookout for the Nine-spotted Lady Beetle where you live and during your travels. The more eyes in the field, the better will be our understanding of the status of this species, which has been the state insect of New York since 1989. Thank you.

ID Tip: Ground Beetle or Darkling Beetle?

I have decided to begin a new, recurring feature here called "ID Tips" that will be designed to help naturalists, amateur and student entomologists, and others solve common and basic problems in insect and spider identification. Our first installment will explain differences between ground beetles (family Carabidae) and darkling beetles (family Tenebrionidae). The two are easily confused, but generally straightforward once you know what to look for.

Ground beetle, Dicaelus sp.; note antennae, exposed jaws

Darkling beetle, Embaphion sp.; note antennae, hidden jaws

Physical Features

One glaring difference between carabids and tenebrionids is the structure of the antennae. In ground beetles, the segments of the antennae are usually longer than wide, giving the antenna the appearance of a near single filament. Darkling beetles have mostly bead-like segments, such that the antenna resembles one of those keychains that closes by pushing the filament between the beads into a clasp. This is not a foolproof character, but works enough of the time that it will help you make a quick determination.

Ground beetle, Calosoma sp.; note antennae, exposed jaws

Darkling beetle, Eleodes sp.; note antennae, concealed jaws

Look also at the front of the head. Are the mandibles (jaws) exposed and directed forward? If so, then you have a ground beetle or another kind of predatory beetle. Conversely, if the mandibles are concealed beneath the clypeus ("upper lip" if you will), then it is likely your specimen is a darkling beetle or another beetle that feeds on vegetation or detritus.

Behavior

Does your beetle move very rapidly by running? This is another characteristic of ground beetles. Many species are so fast that it is a real challenge to catch them for closer examination. Does your beetle lumber along slowly or only run fast when prodded? Chances are you have a darkling beetle then. Many darkling beetles rely on a very dense exoskeleton to repel attacks by predators, and consequently don't feel the need to flee in haste. Desert and prairie species may even have the wing covers fused to help limit water loss.

Ground beetle, Chlaenius sp., that has a stink defense

Does your beetle stand on its head when disturbed? This head-standing behavior is characteristic of the darkling beetle genus Eleodes, and some other closely-related genera. Both darkling beetles and ground beetles can have extremely effective chemical defenses that include pungent, permeating aromatic compounds released from abdominal glands, so smelling your beetle to make an identification is not only a potential exercise in futility, it can be highly unpleasant if not injury-inducing.

Darkling beetle, Helops pernitens, with antennae like a ground beetle (but concealed jaws)

Habitat

Habitat is not a good way to distinguish ground beetles from darkling beetles. Both can be found in a variety of habitats, and are especially abundant and diverse in aridland ecosystems.

Complicating Factors

Because both carabids and tenebrionids are well-defended insects, they are mimicked by a variety of unrelated insects. One prime example is the longhorned beetle genus Moneilema, which mimics Eleodes darkling beetles not only in appearance, but behavior. The longhorned beetles, which feed mostly at night, on cactus pads, move slowly and even stand on their heads like Eleodes. They have no chemical defense to back-up their warning posture, but the bluff works fine on all but the most desperate of insectivores.

Darkling beetle (Eleodes sp.) head-standing

Cactus longhorned beetle (Moneilema sp.) mimicking Eleodes spp.

Another complication is the relatively recent assimilation of two former beetle families into the Tenebrionidae, many of which do not resemble "classic" darkling beetles. These are the comb-clawed beetles (subfamily Alleculinae) and long-jointed beetles (Lagriinae).

Comb-clawed beetle, Hymenorus sp., a type of darkling beetle

Long-jointed beetle, Statira sp., an aberrant darkling beetle

In contrast, the "ironclad beetles" in the family Zopheridae were once members of the Tenebrionidae. They include beetles so well-armored that entomologists have extreme difficulty in pinning specimens that they collect.

Ironclad beetle, Zopherus tristis

No single character is probably reliable by itself, and it is recommended that one use a dichotomous key, in a technical book or online, to reach a firm conclusion on the identity of your beetle. It is also a great idea to invest in a good dissecting (binocular) microscope. Good luck!

Backswimmer or Water Boatman?

Just a short post for “True Bug Tuesday,” addressing an identification problem that many people admit having. I am not an expert on aquatic insects by any means, but differentiating backswimmers (family Notonectidae) from water boatmen (family Corixidae) is fairly straightforward.

Backswimmer swimming upside down

My own experience has shown that backswimmers are generally far more commonly seen by the casual observer than are water boatmen. Backswimmers can even turn up in the fountains, swimming pools, and other artificial water environments water boatmen rarely frequent. Now, if you bother dragging a net through the water, especially over the bottom of a pond or slow-moving stream, then you may see water boatmen at least as frequently as backswimmers, if not more so.

Turn on lights at night anywhere near water and you may bet large numbers of water boatmen showing up, flailing about on the ground. Both water boatmen and backswimmers can fly as adults, but backswimmers seem to be mostly diurnal and will rarely if ever be attracted to lights at night.

Water boatman attracted to light at night

Physically, both kinds of insects do superficially resemble each other. Both are more or less oval or bullet-shaped, and the hind legs are very long, modified for rowing through the water. That is pretty much where the similarities end, however.

Adult backswimmers, at least those of the common genus Notonecta, are much larger than the average water boatman. Backswimmers, in cross section from front to back, have distinctly triangular bodies. They are shaped more like a boat than a water boatman. The top of a backswimmer is keel-like, affording it the ability to swim very rapidly upside down. Water boatmen are more flattened top to bottom.

Water boatman

The front legs of backswimmers are short, but shaped normally, with no obvious modifications. The front legs of water boatmen have spoon-shaped tarsal segments for scooping organic matter into the mouth of the bug. While backswimmers have a four-segmented rostrum (“beak”) they use to bite prey, water boatmen have the beak fused to the head. The face of a water boatman reminds one of an imperial storm trooper from Star Wars.

Water boatman. Note scoop-like front "feet"

Most water boatmen are brown on top, marked with fine, transverse black lines, giving them a slightly corrugated appearance. Backswimmers, by contrast, are usually boldly marked with patches of black, yellowish-brown, red, or white.

Top of backswimmer, © Lynette Schimming

Backswimmers frequent open water where they actively pursue mosquito larvae and other small aquatic insects. Water boatmen normally cruise the bottom, stirring up muck and microscopic organisms that they feed on. Consequently, water boatmen are often difficult to see when you are looking into the water. They are camouflaged, and/or they hide under leaf litter and other bottom debris.

Backswimmer, © Margarethe Brummermann

Look for backswimmers surfacing to take in air with those hydrophobic hairs around their rear end. The hairs also go down the middle of the underside of the abdomen, helping to trap air for their underwater lifestyle.

Source: Lehmkuhl, Dennis M. 1979. How to Know the Aquatic Insects. Dubuque, Iowa: Wm. C. Brown Company Publishers. 168 pp.