KBS023: Insect Abundance

Active

In use from 1988-05-01

Abstract

Sampling Frequency: Weekly during the peak growing season (May-August)

The general occurrence and abundance of insects within each plot is assessed with scouting . Scouting consists of detailed inspection of soil and individual plants for insects within a meter row or a m 2 area of the established sampling area . Sweep samples are taken for foliar insects . Samples of unidentified insects, weeds or pathogens are brought to the laboratory for identification .

Detailed sampling for predator and herbivore abundance is performed with yellow stickypanels . These panels trap ladybird beetle adults, lacewing predators (Carne), lightningbugs (Lampyridae), potato leafhoppers (Empoasca fabae), aphids (Aphidae), corn rootworms (Diabrotica) and possibly others which are attracted to the LTER plot arrangement . In each plot, a trap is placed at each of the 5 baseline sampling stations . Each trap is counted weekly where species and abundances are determined . Sticky panels are replaced at weekly intervals .

Protocol

Introduction

A key aspect of establishing a long term program in insect spatial and temporal dynamics is the development of a sampling
protocol. This includes the use of a standard method of measurement for the species assemblage being monitored and the use of permanent sample site locations distributed throughout the landscape at known geographic locations. The application of permanent sampling sites was used to account for differences in time (weeks, years) without the complication of spatial variation. A new sampling protocol was developed for the insect monitoring within the KBS-LTER. Several factors were considered when developing the method used to sample the selected insect groups:

  1. a method which could be used in different habitats;
  2. simple to maintain the sample device;
  3. low cost;
  4. ease of removal of the sample device due to agronomic practices,
  5. ability to sample a large number of locations over a sizeable geographic area, and,
  6. independent of the observer.

Until 1995 data have been collected weekly from May-August from 210 permanent sample locations from the main LTER site.
Since then 285 stations are sampled weekly over a 12-14 week period each year.

A colored (yellow) sticky trap is used to sample plant dwelling predators (coccinellids, chrysopids, lampyrids). The pitfall trap is used to sample ground dwelling predators (carabids, arachnids, staphylinids). The pitfall trap is a common method to record ground dwelling invertebrate predators. The use of the sticky trap is less commonly used. The consistency of patterns of catch of plant dwelling predators during the six-year study has indicated that sticky traps have the same advantages and disadvantages of the pitfall trap. The use of the selected trapping methods has provided the possibility to conduct the study at larger scales with more groups of invertebrates (other than ground dwelling arthropods), which has enhanced the understanding of the way that invertebrates interact with the landscape.

Plant dwelling insect predators

At each sampling station we place one insect trap. Each trap consists of a double sided cardboard yellow sticky trap (unbaited Pherocon, Zoecon, Palo Alto, CA) suspended 1.2 m above the ground as described in the next figure.

Insect adults are sampled weekly during the growing season (approximately from early May to late August). Insect are identified in the field (using a pictorial key), recorded on sampling sheets, and removed from the traps. Yellow sticky traps are replaced every two weeks. All the data and ancillary information are entered into a computer using a statistical spreadsheet for maintenance and analysis.

In 1995, we initiated the use of a Newton 110 PDA (personal digital assistant) to substitute for sampling sheets in the
field. A special set of sampling software, designed initially for plant dwelling insect sampling needs, but with potential for other sampling protocols, allowed direct capture of all plant dwelling insect directly on the field. At the end of each day data are downloaded directly into a relational database system for subsequent data management and analysis.

Last Update: 15 December 1995

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