understriped diving beetle

(Dytiscus fasciventris)

Conservation Status
understriped diving beetle
Photo by Shylo Morgan
  IUCN Red List

not listed

     
  NatureServe

NNR - Unranked

     
  Minnesota

not listed

     
           
           
           
           
           
           
           
 
Description
 
 

Understriped diving beetle is a large water beetle. It occurs in the Unites States from Maine to Minnesota south to Virginia and Missouri, and in adjacent Canadian provinces. It also occurs in western Canada from Alberta to the Yukon, and in Wyoming. It is found in permanent ponds and marshes with sedges. The larvae, called water tigers, are more often among aquatic plants, while the adults are more often in open, deeper water. Both larvae and adults are voracious eaters, preying on aquatic invertebrates and small fish. Larvae also prey on mosquito larvae in the spring.

Adults are to 1 (22.0 to 27.9 mm) in length. The body is elongated oval, broadest near the middle, and is streamlined, convex both above and below. It is usually brown or brownish-black, sometimes green. On the underside, the rearmost plate of the thorax (metasternum) is brownish-black in the middle. The underside of the abdomen is mostly brownish-yellow to reddish.

The exoskeletal plate covering the first segment of the thorax (pronotum) has a broad pale stripe on the lateral margin. The front margin has a narrow faint pale stripe, a narrow dark reddish stripe, or no stripe all. The rear margin is never striped. The triangular plate (scutellum) between the bases of the wing covers (elytra) is visible.

The elytra on the female always have distinct parallel groves. On the male the elytra are smooth, polished, and sparsely hairy. On both sexes they completely cover the abdomen and there is a pale stripe on each lateral margin. The stripes narrow beyond the halfway point and disappear before reaching the wingtip.

The mouthparts are directed forward. The antennae are thread-like and have eleven segments. The eyes are not notched above the antennae bases.

The rear legs are flattened and much longer than the front and middle legs. The first segment (coxa) of the hind legs is yellow. The fourth segment (tibia) has two spurs at the tip. The smaller spur is as wide or only slightly wider than the larger spur. The last part of the leg (tarsus), corresponding to the foot, has five segments. On the hind legs, the rear margins of the first four tarsal segments are bare, not fringed with golden hairs. The outer margins of each segment are covered with hairs which aid in swimming. On the front legs of the male, the first three tarsal segments are greatly widened, and together form a nearly circular suction disk.

 
     
 

Size

 
 

to 1 (22.0 to 27.9 mm)

 
     
 

Similar Species

 
     
     
 
Habitat
 
 

Permanent ponds and marshes with sedges

 
     
 
Biology
 
 

Season

 
 

One generation per year: April to November

 
     
 

Behavior

 
 

Adults are very good swimmers. They will come to lights.

 
     
 

Life Cycle

 
 

Adults overwinter in permanent waters. They mate in late fall or early spring. The male uses the suction disks on its front legs to hold the female while mating.

 
     
 

Larva Food

 
 

Mosquito larvae, aquatic invertebrates, and small fish

 
     
 

Adult Food

 
 

Aquatic invertebrates and small fish

 
     
 
Distribution
 
 

Distribution Map

 

Sources

24, 27, 29, 30, 82.

 
  8/31/2021      
         
 

Occurrence

 
 

Common

 
         
 
Taxonomy
 
 

Order

Coleoptera (beetles)  
 

Suborder

Adephaga (ground and water beetles)  
 

Superfamily

Dytiscoidea  
 

Family

Dytiscidae (predaceous diving beetles)  
 

Subfamily

Dytiscinae  
 

Tribe

Dytiscini  
 

Genus

Dytiscus  
       
 

Synonyms

 
 

 

 
       
 

Common Names

 
 

understriped diving beetle

 
       

 

 

 

 

 

 

 

Glossary

Elytra

The hardened or leathery forewings on an insect used to protect the fragile hindwings, which are used for flying, in beetles and true bugs. Singular: elytron.

 

Pronotum

The saddle-shaped, exoskeletal plate on the upper side of the first segment of the thorax of an insect.

 

Scutellum

The exoskeletal plate covering the rearward (posterior) part of the middle segment of the thorax in some insects. In Coleoptera, Hemiptera, and Homoptera, the dorsal, often triangular plate behind the pronotum and between the bases of the front wings. In Diptera, the exoskeletal plate between the abdomen and the thorax.

 

Tarsus

On insects, the last two to five subdivisions of the leg, attached to the tibia; the foot. On spiders, the last segment of the leg. Plural: tarsi.

 

Tibia

The fourth segment of an insect leg, after the femur and before the tarsus (foot). The fifth segment of a spider leg or palp.

 

 

 

 

 

 
 
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Shylo Morgan

 
 

First of all I love your site.

Can you tell me what kind of bug this is? I assume it's a beetle but I've never seen one like this. Or this huge.

I seen my first ever cicada last year. I was reading after males mate they just kinda Drop dead.  Is that what happened here?

  understriped diving beetle  
           
    understriped diving beetle   understriped diving beetle  
           
    understriped diving beetle      
           
 

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  Shylo Morgan
8/23/2021

Location: Ada, MN

First of all I love your site.

Can you tell me what kind of bug this is? I assume it's a beetle but I've never seen one like this. Or this huge.

I seen my first ever cicada last year. I was reading after males mate they just kinda Drop dead.  Is that what happened here?

understriped diving beetle

 
           
 
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Created: 8/31/2021

Last Updated:

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