Illinois Natural History Survey - University of Illinois

The root feeding weevil on purple loosestrife

At present we have no pictures of this beetle whose scientific name is Hylobius tranversovitattus. It is dark reddish-brown, a bit smaller than a dime with a long snout. Adults are nocturnal so it is very difficult to find them in the field. It has been in the United States for several years and was first released in 1992. A brief summary of the biology is given below.

Winter

Hylobius survives the winter as adults, that burrow into the surface litter and go dormant, or as larvae inside roots where they also go dormant until the warmer temperatures of spring raise the soil and root temperature.

Spring and Early Summer

Overwintering adults emerge from diapause in the spring and begin to feed on leaf and stem tissue. Eggs are deposited in the stem just above ground level, about 1 -2 per day. A single female will live for 2-3 years and may lay up to 300 eggs.

Larvae that have overwintered in the roots, begin to feed as the soil warms up, complete their development, pupate and emerge as adults in mid to late summer. These new adults feed prior to going into dormancy for the winter. Some larvae may take more than one full summer to reach complete development within the root.

Late Summer and Fall

Adults that have just emerged from roots and those that have finished laying eggs for the year will feed then move to overwintering sites where they remain dormant until spring. Larva that have hatched from eggs laid in the stems continue to feed and grow until the temperature drops to the point where they go dormant.

Release procedure for Hylobius

Eggs are collected from females kept in colonies in the lab. These are stored in distilled water for transport to the field. In the field stems are cut a few inches above the ground, a small depression is made in the cut stem, an egg is inserted with a fine paint brush and a cap of modelling clay placed over the cut stem.

The picture at right shows one of the stems that was inoculated and capped. For the results of this inoculation see the picture below.

 

 

 

 

 

Once inoculated into the stem the egg hatches and the larva begins to feed on the inside of the stem. As it feeds it moves towards the ground and the root where it will remain feeding until it is fully grown larva and pupates.

The picture at the right shows a stem in which a larva has eaten the center as it moved towards the root. The fine material in the stem is the chewed up plant stem.

Information on this page maintained by David Voegtlin.



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