Sap Beetle: All You Need to Know in a Nutshell

Sap beetles, also known as driedfruit beetles, belong to the family Nitidulidae and are a complex of several closely related species. These small insects, ranging from 1/8 to 1/4 inch in size, can be found in various places, particularly in gardens or agricultural settings. Some common species include the Carpophilus hemipterus, Carpophilus freemani, and the confused sap beetle.

You might encounter sap beetles when you grow fruits or vegetables in your garden. These beetles are attracted to ripe, fermenting, or decaying produce and can cause significant damage. They also have a distinct feature: their antennae end in a club-like shape that can be helpful in identifying them.

Understanding the behavior, life cycle, and management methods for sap beetles is essential in dealing with these pests successfully. By the end of this article, you’ll be well-equipped with all the information you need to tackle any sap beetle issues that may arise in your garden or fields.

What Is a Sap Beetle?

A sap beetle, belonging to the family Nitidulidae, is a type of small insect that is attracted to sweet, overripe, or decomposing fruits and vegetables. You’ll often find them in gardens or farms where fruits and vegetables are grown. There are more than 180 species of sap beetles, and they come in various shapes and colors, usually black or dark.

For instance, a common sap beetle species is the four-spotted sap beetle, also known as the picnic beetle. This beetle is 1/4 inch long, shiny black, and has four yellowish dots on the wing covers. Another example is the strawberry sap beetle, which can cause damage to strawberry plants and fruits.

Sap beetles are general scavengers, and their diet can include sap, decaying plant materials, fungi, and sometimes even other insects. Due to their feeding behavior, sap beetles can be considered minor pests in gardens or farms.

Some key features of sap beetles are:

  • Antennae with a club or knob at the end
  • Usually dark-colored, black or brown
  • Small in size, ranging from 1/8 to 1/4 inch in length

While sap beetles may be a nuisance to fruits and vegetables in your garden, they are also part of the natural ecosystem. Preventative measures like timely harvest of ripe crops and removal of decomposing plant materials can help reduce their presence.

Characteristics of Sap Beetles

Physical Attributes

Sap beetles are small insects with antennae, an oval shape, and wing covers. They are usually shiny black in color, with their abdomen slightly protruding. For example, the strawberry sap beetle measures about 1/8 inch long and has a more flattened oval shape.

Life Cycle

The life cycle of sap beetles consists of four stages: egg, larva, pupa, and adult. They usually overwinter as adults, meaning they survive the winter in their adult form.

Genera of Sap Beetles

Some common genera of sap beetles include the dusky sap beetle (Carpophilus lugubris) and the strawberry sap beetle (Stelidota geminata).

Sap Beetles as Pests

Sap beetles can be pests of various crops, including vegetables, corn, sweet corn, berries, and tomatoes. They can be secondary pests, but may act as primary pests if populations are high, as seen with corn crops.

Sap Beetle-Plant Interactions

These beetles are often attracted to ripe and overripe produce, as well as decaying fruit. They can be found on strawberries, fruit crops, muskmelon, field corn, raspberries, and more.

Damage Caused by Sap Beetles

Sap beetles can cause considerable damage to crops. They feed on corn silk, pollen, corn ears, fruit crops like strawberries, and fermenting plant juices. They can spread fungi, furthering decay and leading to infestation.

Control and Prevention of Sap Beetles

To control and prevent sap beetle infestations:

  • Harvest crops promptly when ripe.
  • Remove decayed and overripe fruits.
  • Prevent damage from primary pests, such as corn earworms.

Following these steps can minimize the likelihood of sap beetle damage to your crops.

Reader Emails

Over the years, our website, whatsthatbug.com has received hundreds of letters and some interesting images asking us about these insects. Scroll down to have a look at some of them.

Letter 1 – Picnic Beetle

 

the mysterious beer bug
Hi, Bugman!
I live in south-eastern Ontario, and during all of the summers of my childhood, our picnics were plagued by little black and white beetles about a quarter of an inch long that loved our food and would bite if you weren’t careful. Coming from a family of teetotalers, we called them “food bugs”. Later, I heard them called “beer bugs”, but I’ve not yet come across a person who knows what kind of beetle they actually are, and my web research has revealed no clues. Can you enlighten me? Thanks!
Jaimie Cowles

Hi Jaimie,
Our initial impression based on the shape and antennae, is that this is either a Sexton Beetle in the genus Nicrophorus, or some other Carrion Beetle in the family Silphidae. Sexton Beetles are characterized by red markings and we couldn’t find any matches on Bugguide. We are going to try to contact Eric Eaton, but we know he is having computer problems and may not respond for some time. Meanwhile, perhaps a reader can assist.

Update from Eric Eaton (08/04/2008)
Daniel:
The black beetle with the four yellow marks is a sap-feeding beetle in the family Nitidulidae. This one is probably Glischrochilus quadrisignatus, better known as a “picnic beetle.” They will sometimes fly to picnics in large numbers, attracted mostly by fermenting fruit, and probably alcohol, too. Not harmful in the least, just annoying:-)
Eric

Letter 2 – Four Spotted Sap Beetles attracted to Vinegar

 

Subject: I think this is a Silphidae
Location: Reese, MI
July 1, 2012 8:21 pm
I have an infestation of these bugs. By looking at the shell I think that these are from the Silphidae family. But all the information that I have found said that Silphidae do not bite but these do. They seem to come out at night and are attracted to apple cider vinager. Please help me identify these pests and come up with a way to keep them away from my deck!!!!
Thank you
Signature: Tireman2000

Four Spotted Sap Beetle

Dear Tireman2000,
Why ever do you keep a container of vinegar outside if it attracts these Four Spotted Sap Beetles which are also called Picnic Beetles or Beer Bugs.  We identified them first by doing a web search for vinegar beetles and we found a Sap Beetle on the Cape Beekeeping website.  The website author traps beetles in his bee hives by using mineral oil and cider vinegar, and he had a photo posted that was identified as a Sap Beetle that looked like your beetle.  Armed with that information, we found the Four Spotted Sap Beetle,
 Glischrochilus quadrisignatus, on BugGuide where it states they eat:  “various fermenting substances” and they are “attracted by the odour of fermenting fruits and vegetables; the adult beetles fly into beer or soft drinks at summer picnics.”  Again, please let us know what you are doing with the vinegar.

Vinegar attracts Sap Beetles

 

Letter 3 – 4-Spotted Sap Beetles

 

Elm Tree Bug
Location:  Eastern Colorado
September 22, 2010 2:26 pm
Dear Bugman,
I am searching for an identification for the group of bettles in the enclosed photo. They have gathered in a sap pocket of an American Elm Tree in Eastern Colorado.
Signature:  Daniel

Sap Feeding Beetles

Dear Daniel,
It is difficult to make out the details of the individuals in your photo, but we nonetheless believe they are Sap Feeding Beetles in the family Nitidulidae, possibly
Glischrochilus quadrisignatus, the 4-Spotted Sap Beetle which is pictured on BugGuide.

Thank you very much for the information!  That looks to be the correct match!  What a great service you offer!  I would recommend whatsthatbug.com to anyone!
Very grateful,
Daniel

Authors

    by
  • Bugman

    Bugman aka Daniel Marlos has been identifying bugs since 1999. whatsthatbug.com is his passion project and it has helped millions of readers identify the bug that has been bugging them for over two decades. You can reach out to him through our Contact Page.

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  • Piyushi Dhir

    Piyushi is a nature lover, blogger and traveler at heart. She lives in beautiful Canada with her family. Piyushi is an animal lover and loves to write about all creatures.

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5 thoughts on “Sap Beetle: All You Need to Know in a Nutshell”

  1. I grow strawberries in Indiana. Last year, I had trouble with some small beetles picking out the largest ripest berry and burrowing into. Any chance this could be the same beetle? If not, any ideas what it could be?

    Reply
  2. Hi, here vacationing in Barbados, my girlfriend found two of these beetles as we were enjoying our dinner, unfortunately squashed them before I could identify.

    Reply
  3. I came across this post from Googling “picnic beetles.” We now live in Michigan where they are not a problem, but years ago we lived in central Ohio, and had no end of trouble with these beetles that my wife – an avoid gardener – called picnic beetles.

    They were about the size and shape of cucumber beetles (proportionately narrower than the picture) but were black, and had a white spot on each wing. They are the devil’s own spawn, eating off the plants what we eat. If there’s fruit, they eat the fruit; if you eat the leaves, they eat the leaves.

    This was over 30 years ago, and pre-internet, so I was left to my reference books to try to find a natural control, but couldn’t even find mention of them buy that name. I found a natural control by accident. I was sitting out by our garden with a glass of wine and felt something on my hand. It was a picnic beetle, apparently attracted by the smell of the wine.

    I went out a bought a couple bottles of cheap wine and poured it into a cookie sheet placed in the garden. The next day the cookie sheet was choked with drowned picnic beetles.

    Hope this helps.

    Reply
  4. On a related note, whenever I try to sleep outside with my exposed buttocks covered with beer batter, I am woken up prematurely by these guys! What gives???

    Reply

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