Ask The Entomologist

Ask the Entomologist: Ladybugs – which types bite?

First off, this is an excellent question.
All ladybeetles have jaws and the ability to bite, but some certainly seem to do so more often.

I’m fond of this question for more than that, though.
I got my start in entomology as a highschooler in South Dakota. Dr. Louis Hesler, a USDA lab scientist who specialized on ladybeetles took me under his wing, and helped me learn to identify them. I specialized in dissecting and identifying tiny ladybeetle species, often less than 1/10th of an inch long. That was the first time in my life that I felt I was doing work that couldn’t be easily replaced, and it was an addictive feeling.

If you have ladybeetles in your home, and have been bitten by them, I’d expect them to be Multicolored Asian Ladybeetles. Other ladybeetles are quite capable of biting, too, even if they don’t do so terribly often.
It’s more a question of what kind of ladybeetles we regularly encounter in our homes.

This past autumn I saw just over a dozen species of ladybeetles around our place… and I wasn’t searching for them. For comparison, South Dakota is currently known to have 80 species of ladybeetles. Chances are good that Montana has a similar or higher number. Despite all the ladybeetle species we had outdoors this summer, the only species I’ve seen in our home this winter is the Multicolored Asian Ladybeetle.

Why are these beetles in our homes? To avoid the cold weather.
While most ladybeetles need to avoid freezing to survive winter, not all do so in the same way.

European ladybeetles, such as the Seven-Spotted Ladybird Beetle (now common in North America as well) often overwinter in leaf litter. New World ladybeetles, such as the Convergent Ladybeetle, tend to overwinter inside rotting trees, much like Cluster Flies further from human structures do. Smaller ladybeetles are known to overwinter inside ant burrows, feeding on their larvae through the winter.

The Multicolored Asian Ladybeetle, has a different history, though. This species has lived alongside soybean farming for ages – the soybean was domesticated in the 11th Century BC. The Asian Ladybeetle’s ancestors overwintered in barns after the soybean harvests, and its descendants seek out shelter in human-made structures as well… It is this behavior that brings them into conflict with humans more than other species of ladybeetle.

Not all entomologists think that Asian Ladybeetles are likely to bite.
This write-up found that only about 1/4 of Asian Ladybeetles bit the author when given the opportunity… When not removed from his hands after they began biting, the Asian Ladybeetles happily feed on him for about a half hour. I suspect few people besides entomologists have personally experienced this phenomenon, however. One can see how similar behavior on fruits can quickly make these into pests.

How can I prevent the Asian Ladybeetles from invading my home in the winter?
Well, I can tell you what doesn’t work, and what ostensibly should work.

Putting up “Ladybug Houses” will not work at all. These beetles aren’t stupid – they can tell it’s warmer in your home than in the ladybug house, so your home will be their clear preference for winter quarters.

It’s theoretically possible to caulk your house so well that insects won’t be able to get inside. In practice, I don’t think this is viable at all. Good luck getting all those 1/16th inch cracks closed! There will always be a few tiny gaps that you miss, and the insects will invite themselves in to the warmth.

If you feel the need to remove your ladybeetle infestation, I’d suggest vacuuming. With a good suction attachment, you’ll be able to remove the Asian Ladybeetles without smushing them and making stains. I’d suggest emptying the vacuum bag promptly, or they’ll crawl out and continue on their merry way. Purdue Extension advocates using socks when vacuuming bugs.

Vacuuming them up can also be a wise idea if you’ve got a dog who likes to eat ladybeetles. Consuming sufficiently large quantities of ladybeetles, regardless of the species, can make your pets sick. But, as Paracelsus said, “The dose makes the poison”. It takes a special dog to eat one ladybeetle and decide to follow it up with fifteen more. I suspect your beasties may be a bit more discerning.

An excerpt from my mentor’s poster of the Ladybeetles of South Dakota.
I’ve observed many of these species here in Montana as well.

Ask The Entomologist

Ask the Entomologist: Bug on my kitchen wall

“Is this a stink bug? Our house has a few of these, and they’re often walking on the walls. Why?”

Your particular leaf-footed bug is Leptoglossus occidentalis, the Western Conifer Seed Bug.
Very nice photo, by the way.

This isn’t a stink bug, but that’s a very good guess!
This is a leaf-footed bug, a close relative of the stink bugs – they’re both members of Hemiptera, what entomologists call “the true bugs”. Beyond this, leaf-footed bugs and stink bugs both belong in Infraorder Pentatomorpha. While leaf-footed bugs do emit a strong smell when stressed or handled, but it’s not nearly as strong as a stink bug’s scent, in my experience.

These bugs are similar in behavior as well – they have piercing mouthparts, and tend to be herbivorous, especially seed-feeding. Both have been crop pests – stinkbugs are detrimental to agricultural pursuits like soy farming, while leaf-footed bugs tend to be more damaging in tree plantation contexts. In some regions, both may be present as minor citrus farming pests.

Here’s a stink bug I met this fall, perched on a burdock leaf. Note the differences:
The leaf-footed bug is slender and has fins on its hind legs.
The stink bug is stout in comparison and has larger spines on its shoulders.

However, when the weather turns cold, both stink bugs and leaf-footed bugs seek shelter from the elements. In winter, both stink bugs and leaf-footed bugs build up protective alcohol-based compounds in their blood that make it much more difficult for them to freeze. However, if they do end up freezing, they die. Leaf-footed bugs are what entomologists would call “cold-tolerant, freeze-avoidant“. Their quest to find someplace warm to spend the winter sometimes leads them to bother us indoors. Without human homes to invade, leaf-footed bugs and stinkbugs both tend to overwinter inside large dead trees.

While they may be annoying for a time, rest assured that neither stink bugs nor leaf-footed bugs are harassing your houseplants this winter. During overwintering, these bugs avoid feeding – after all, the more moisture they take in, the more likely it is that ice crystals could form inside them. However, many leaf-footed bugs do release aggregation pheromones which spread the news that your home is a great warm place to wait out the winter.

As for why your new houseguests are walking on your walls, that I don’t have as good an answer for.
I imagine that your walls might be warmer than the floor, and that could make them more attractive. I’d also hazard a guess that your leaf-footed bugs prefer being on inside walls, rather than outside walls.

Thank you for the question!


Adapting to the Cold- Conifers

As it starts to get colder, animals have several options. “Leave for warmer places” is the primary strategy of migratory birds. Many animals take the “Find somewhere warm and stay there” strategy that is my personal approach to winter. Many animals find warm dens for the winter and hibernate, avoiding the cold and snow altogether. Finally, there is the “Bundle up real warm and live with it” strategy of of some of the fluffier varieties of wildlife. Of course, some mix and match of strategies is common; Venturing out for food and returning to a warm den is common enough.

But plants have one major handicap to their potential strategies. Unlike animals, which can move, plants are rather stuck. This means that a tree has no choice but to go with the “Live with it” strategy for coping with cold. Consequently, the trees we have in the area tend to be rather well equipped for that strategy.

We’re dominated by evergreens, or conifers. Conifers do not generally shed their leaves in the fall. The reason for this is that they don’t generally need to. The needles of a conifer are shaped very differently then the leaves of a broad-leafed tree (such as a maple), despite having pretty much the exact same purpose. Not losing all the leaves (they will lose some to wear and tear) is a huge advantage; it means that conifers can keep doing photosynthesis as long as there’s enough warmth and light to do so.

Why the needle shape? Snow load. Everything about the shape of a conifer helps with snow load. A tree is a lot like a roof, in that it can be damaged by the weight of accumulating snow. Conifer needles are shaped to avoid accumulating snow, and each needle will hold far less snow than the leaf of a deciduous tree. The tree itself is shaped to shed snow, with branches that tend to be fairly flexible. While branches may break from a particularly wet (and thus heavy) accumulation of snow, for the most part they bend and shed snow.

Freezing is, for most living things, a pretty serious problem. Water expands as it freezes, and at the cellular level this is quite destructive. Conifers avoid serious damage from this by allowing water outside of the cells to freeze, and by having cell walls that are harder, hard enough to generally withstand the pressure of expanding ice.

The final challenge of winter is not drying out. For conifers, that especially thick waxy coating on the needles is a way of preventing that.

Lessons to be learned from conifers?

  • Too much snow piled atop one is a bad thing. Being cone shaped helps
  • A waxy coating prevents water loss (chapstick?)
  • Don’t freeze