Invertebrates

Task 2: Working with invertebrates.

Task 2

Working with invertebrates

I attended a teaching session on 25 September 2023, given by Dr Matthew Bulbert (Senior Lecturer in Conservation Ecology) that included practical tasks of sorting and identifying a collection of invertebrates to family level.

The following questions were posed, with my answers below.

What did you learn from this practical?

Use of a microscope in a lab setting e.g. focussing.

Difficulty in positioning specimens such that key features can be observed e.g. separating legs, turning over to view underside, or mouthparts.

The feature required to move on in a dichotomous key is not always clear or visible in specimens.

Coleoptera have elytra (hardened forewings).

The piercing-sucking mouthpart of Hemiptera is held under its head.

Images and ID details of 5 invertebrate orders.

Coleoptera

  • 3 pairs of jointed legs.

  • 2 pairs of wings.

  • Hardened front wings (elytra).

  • 12 or less segments in antennae.

  • Biting mouthparts including segmented palps.

Coleoptera under microscope
Coleoptera under microscope

Images and ID details of 5 invertebrate orders.

Araneae

  • 4 pairs of jointed legs.

  • No antennae.

  • No large, pincer-like palps.

  • Constricted 'waist' between thorax and abdomen.

Araneae under microscope
Araneae under microscope

Images and ID details of 5 invertebrate orders.

Hymenoptera

Note: when following the keys, because one has wings and the other is apterous I had to follow 2 separate keys.

Hymenoptera under microscope
Hymenoptera under microscope

Winged:

  • 2 pairs of wings

  • No elytra, wings membranous with venation.

  • Wings not held over body (roof-like).

  • Antennae with 9 or more segments.

  • Pronotum not saddle shaped or covering head.

  • Constricted 'waist' between thorax and abdomen.

  • Tarsi 4- or 5-segmented.

Apterous:

  • Antennae unbranched.

  • Mouthparts not sucking tube.

  • Pronotum does not extend over the head.

  • No terminal tails.

  • Constricted 'waist' between thorax and abdomen.

Images and ID details of 5 invertebrate orders.

Diptera

  • 3 pairs of jointed legs.

  • 1 pair of wings.

  • No appendages on tip of abdomen.

  • Halteres behind wings.

Diptera under microscope
Diptera under microscope

Images and ID details of 5 invertebrate orders.

Hemiptera

  • 3 pairs of jointed legs.

  • No wings.

  • Mouthparts form a sucking tube, held under the body.

  • Mouthparts without segmented palps.

Hemiptera under microscope
Hemiptera under microscope

Evidence of sorting

Tube of specimens deposited onto a petri dish.

Specimens unsorted
Specimens unsorted
Sorting specimens
Sorting specimens

Me separating the specimens and putting into preliminary groupings based on rough morphology.

Sorting specimens to order
Sorting specimens to order

Me sorting the specimens after identifying the order they belong to.

Specimens grouped into their orders.

Specimens grouped by order
Specimens grouped by order

Which of the tools used for identifying the orders did you find easiest and why?

For this practical I was directed to use a paper-based dichotomous key (Tilling, 2014). After identifying a few specimens it was easier to go through some of the questions quickly, although a matrix key would have potentially allowed me to overcome some of the blockers I encountered.

Provide an example of passive versus active sampling techniques

and the kind of invertebrates you might capture in the different techniques

Active sampling techniques may include:

  • Sweep net: to capture mobile invertebrates, those that may fly or crawl on vegetation e.g. Coleoptera, Araneae, Hemiptera

  • Dip net: captures aquatic invertebrates

Passive sampling techniques may include:

  • Pitfall trap: Can be simple plastic container in a hole in the ground. Has a cover placed over it to prevent bycatch and it filling with rainwater. This can be used to capture invertebrates that move across the surface of the ground such as Araneae, Coleoptera - especially Carabidae (Henderson, 2016) and Diplopoda. May be baited.

  • Berlese funnel (Tullgren funnel): used to find organisms in soil. It has a heat source at the top that dries the soil. Organisms move downwards towards the wetter, colder and darker area; go through a sieve and then fall into a jar. Used to sample invertebrates that live amongst the leaf litter and soil.

  • Malaise trap: a type of Flight Interception Trap. Captures flying invertebrates e.g. Lepidoptera, Diptera

Pitfall trap, Tullgren funnel and Malaise trap diagrams
Pitfall trap, Tullgren funnel and Malaise trap diagrams

Acknowledgments

Many thanks to Emma Cansdale (Laboratory Technician - Environmental Sciences) who kindly setup the microscope and specimens again so that I could take images of the 5 orders of invertebrates that were present in the sample.

References

Tilling, S. (2014) A key to the major groups of British terrestrial invertebrates. 2nd edition. Telford: FSC.

Henderson, P. A. (2016) Ecological Methods. Newark: John Wiley & Sons, Incorporated.

Sutherland, W. J. (2006) Ecological census techniques : a handbook. 2nd edn. Cambridge, UK: Cambridge University Press.

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