Tag Archives: Richard Southwood

Entomological classics – The D-Vac, Vortis and other motorised suction samplers

I think that all field entomologists of a certain age, certainly those of us over 60, are very familiar with the roar of a hot and smoky two-stroke engine in our ears, coupled with oily hands, aching shoulders and sometimes the smell of burning.  Some younger entomologists may also have had this joyful experience but I suspect they are in a minority among their peers.  The dreaded D-Vac, or to give it its more formal name, The Dietrick Vacuum Sampler was, for a long time, the entomological gold standard in the world of motorised insect sampling.

Part of the UEA cereal aphid research group demonstrating unsafe use of the D-Vac 😊

The D-Vac was the brain wave of an American entomologist Everett Dietrick, who at the time was working on the biological control of the alfalfa aphid, Therioaphis maculata (Dietrick et al., 1959). Their research was hampered by the time they were having to spend estimating the numbers of all the arthropods found in alfalfa fields; they needed a standard sampling method that would allow them to get good estimates of everything rather than using different, and thus time-consuming, methods for each arthropod group.  Essentially, think of a D-Vac as motorised sweep net.  The idea of replacing sweep netting with, in theory at any rate, a non-human biased method* was not new.  Hills (1933) in describing a motorised vacuum pipette for sampling leaf hoppers in beet points out that it is an adaptation of a device put together by a lab assistant in 1926.

The first motorised suction sampler? From Hills (1933) – The modified pipette collector

The first and even clumsier model of the D-Vac (Dietrick et al., 1959), but I suspect more pleasant to use than the back-pack version 🙂

The new improved back-pack version (Dietrick, 1961).  In my experience not very comfortable and on one occasion burst into flames while I was wearing it!

This could, with the aid of a handy pole be used to sample from the top of tall bushes. Not something I have tried so I can’t comment.

While searching for the earliest reference to a motorised suction device that was not a Pooter, I came across one invented a few years earlier than the D-Vac and used by the late, great Southwood of Ecological Methods fame among others, during his PhD (Southwood, 1955; Johnson et al., 1955), which I guess means that it was in operation well before 1955, although the actual full description was not published in a journal until a couple of years later (Johnson et al., 1957).

An earlier suction device used by the late great Southwood during his PhD (1955) (From Johnson et al., 1957).

Ensuring constancy of sample area (From Johnson et al., 1957)

It really does look like the vacuum cleaner we had when I was a kid 🙂

Amusingly, one of the early attempts to replace the D-Vac was actually based on this very vacuum cleaner (Arnold et al., 1973)

I was interested to see that the Johnson apparatus used a barrel to delineate the sample area, something advocated by my colleague Andy Cherrill (Zentane et al., 2016) when using his patent G-Vac, or “Chortis” as we jokingly call it 🙂

A couple of years after I started at Silwood Park and became involved in running the final year field course, a new and revolutionary insect suction sampler appeared on the market – The Vortis™ (Arnold, 1994).  This was lighter than the D-Vac, did not need a bag or net, easier to start, had an ‘idle’ function and mercifully did not have to be carried on your back 🙂

The Vortis™, overall a much pleasanter way to sample insects and generally much easier to start.  Invented in 1993 (Arnold, 1994).


Although not cheap, it was less expensive than the D-Vac. This became my suction sampler of choice although we kept our D-vac in good running order so that the students could compare the two samplers.  Surprisingly, few, if any, of the many users of The Vortis™ have done similarly, most just referring to the original description by Arnold (1994), e.g. Mortimer et al., (2002).  This is in marked contrast to the many studies that have compared the D-Vac with sweep-netting, pitfall trapping and swish net sampling (e.g. Johnson et al., 1957; Henderson & Whittaker, 1977; Hand, 1986; Schotzko & O’Keeffe, 1989; Standen, 2000; Brook et al., 2008). There is also a hand-held version of the D-Vac if anyone wants to compare that with the back-pack version.

Jan Dietrick poses with a D-Vac insect Vacuum in Ventura, Calif., on Monday, Oct. 16, 2006. (Photo by Bryce Yukio Adolphson/Brooks Institute of Photography ©2006) http://bryceyukioadolphson.photoshelter.com/image/I0000pmiujJcoGBI

This one looks easier to use than the backpack version but I have never seen it in operation. I am guessing that this was produced in response to the invention of the Vortis™.

Entomologists tend to have limited budgets when it comes to equipment, or anything for that matter, so it is not surprising that they soon came up with the idea of adapting garden leaf blowers into lightweight, inexpensive insect suction samplers (e.g. De Barro, 1991; Stewart & Wright, 1995). These are collectively known as G-Vacs (Zentane et al., 2016) presumably as a reference to their garden origin.

Andy Cherrill test driving his “Chortis” 🙂


My colleague Andy Cherrill has compared the catch composition of his own particular G-Vac with that of the Vortis™ and satisfied himself that it is as good as, if not better than the Vortis™ (Cherrill et al., 2017).  Importantly the cost of a G-Vac means that you can get, at least in the UK, six for the same price as a single Vortis™.

I leave you with two fun facts; the two largest motorised insect suction samplers that I have come across are both from the USA (where else?).  The first, mounted on the front of a truck, was used to collect parasites for the biological control of alfalfa aphids.

(1957) http://www.dietrick.org/articles/deke_truckvac.html  Used to collect parasites for mass release against alfalfa aphids.


The second, mounted on the front of a tractor was used to control Lygus bugs in strawberry fields in California (Pickel et al., 1994).  The driver/operator in the second example seems to be taking Health & Safety issues a bit more seriously than the team in the first 🙂

Lygus bug control in strawberries, California http://calag.ucanr.edu/Archive/?article=ca.v049n02p19



Arnold, A.J. (1994) Insect suction sampling without nets, bags or filters. Crop Protection, 13, 73-76.

Arnold, A.J., Needham, P.H. & Stevenson, J.H. (1973) A self-powered portable insect suction sampler and its use to assess the effects of azinphos methyl and endosulfan on blossom beetle populations on oil seed rape. Annals of Applied Biology, 75, 229-233.

Brook, A.J., Woodcock, B.A., Sinka, M. & Vanbergen, A.J. (2008) Experimental verification of suction sampler capture efficiency in grasslands of differing vegetation height and structure. Journal of Applied Ecology, 45, 1357-1363.

Cherrill, A.J., Burkhmar, R., Quenu, H. & Zentane, E. (2017) Suction samplers for grassland invertebrates: the species diversity and composition of spider and Auchenorrhyncha assemblages collected with Vortis (TM) and G-vac devices. Bulletin of Insectology, 70, 283-290.

De Barro, P.J. (1991) A cheap lightweight efficient vacuum sampler.  Journal of the Australian Entomological Society, 30, 207-20.

Dietrick, E.J. (1961) An improved backpack motor fan for suction sampling of insect populations.  Journal of Economic Entomology, 54, 394-395.

Dietrick, E.J., Schlinger, E.I. & van den Bosch, R. (1959) A new method for sampling arthropods using a suction collecting machine and modified Berlese funnel separator.  Journal of Economic Entomology, 52, 1085-1091.

Dietrick. E. J., Schlinger. E. I. & Garber, M. J. (1960). Vacuum cleaner principle applied in sampling insect populations in alfalfa fields by new machine method. California Agriculture January 1960, pp. 9-1 1

Doxon, E.D., Davis, C.A. & Fuhlendorf, S.D. (2011) Comparison of two methods for sampling invertebrates: vacuum and sweep-net sampling. Journal of Field Ornithology, 82, 60-67.

Hand, S.C. (1986) The capture efficiency of the Dietrick vacuum insect net for aphids on grasses and cereals. Annals of Applied Biology, 108, 233-241.

Henderson, 1. F. & Whitaker, T. M. (1977). The efficiency of an insect suction sampler in grassland. Ecological Entomology 2, 57-60.

Hills, O.A. (1933) A new method for collecting samples of insect populationsJournal of Economic Entomology, 26, 906-910.

Johnson, C.G., Southwood, T.R.E. & Entwistle, H.M. (1955) A method for sampling arthropods and molluscs from herbage by suction.  Nature, 176, 559.

Johnson, C.G., Southwood, T.R.E. & Entwistle, H.M. (1957) A new method of extracting arthropods and molluscs from grassland and herbage with a suction apparatus.  Bulletin of Entomological Research, 48, 211-218.

Mortimer, S.R., Booth, R.G., Harris, S.J. & Brown, V.K. (2002) Effects of initial site management on the Coleoptera assemblages colonising newly established chalk grassland on ex-arable land. Biological Conservation, 104, 301-313.

Pickel, C., Zalom, F.G.,  Walsh, D.B. & Welch, N.C. (1994) Efficacy of vacuum machines for Lygus Hesperus (Hemiptera: Miridae) control in coastal California strawberries. Journal of Economic Entomology, 87, 1636-1640.

Schotzko, D.J. & O’Keeffe, L.E. (1989) Comparison of sweep net., D-Vac., and absolute sampling., and diel variation of sweep net sampling estimates in lentils for pea aphid (Homoptera: Aphididae)., Nabids (Hemiptera: Nabidae)., lady beetles (Coleoptera: Coccinellidae)., and lacewings (Neuroptera: Chrysopidae). Journal of Economic Entomology, 82, 491-506.

Southwood, T.R.E. (1955). Some Studies on the Systematics and Ecology of Heteroptera.—Ph.D. thesis, University of London.

Standen, V. (2000) The adequacy of collecting techniques for estimating species richness of grassland invertebrates. Journal of Applied Ecology, 37, 884-893.

Stewart, A.J.A. & Wright, A.F. (1995) A new inexpensive suction apparatus for sampling arthropods in grassland.  Ecological Entomology, 20, 98-102.

Zentane, E., Quenu, H., Graham, R.I. & Cherrill, A.J. (2016) Suction samplers for grassland invertebrates: comparison of numbers caught using Vortis and G-vac devices.  Insect Conservation & Diversity, 9, 470-474.



Filed under Entomological classics

The Dead Entomologists Society

The late and the great: who are the most influential dead entomologists?

In the run-up to the Christmas holidays an ex-student of mine, Andy Salisbury, now at RHS Wisley, and I were discussing who were the most influential dead entomologists ever.  We had begun our discussion discussing Harold Maxwell-LeFroy, http://en.wikipedia.org/wiki/Harold_Maxwell-Lefroy, who among other claims to fame, was the first editor of Annals of Applied Biology http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1744-7348 , the founder of Rentokil and former Professor of Entomology at Imperial College.  He was also famous for having killed himself accidentally whilst trying out a pesticide.

Lefroy conversation

Dead entomologists

Up until the early part of this century he was commemorated in the Biology Department at Imperial College’s Silwood Park Campus with a laboratory named after him; sadly with the move into the new Hamilton Building this no longer exists.

We agreed that the great Alfred Russel Wallace was the most influential entomologist of all time; we felt that claiming Darwin as an entomologist, although famous for his beetle collecting, and despite being a Fellow of the Royal Entomological Society, might be a step too far.  So after Wallace, who was the most influential dead entomologist?

I think that this depends on how you define influential – for entomologists of my generation and the one before us, i.e. those born between 1930 and 1960; Imms and Wigglesworth are probably the two who most influenced us mainly because they were our recommended undergraduate texts  (those were the days when you could do entomology  in the UK as an undergraduate);

Wigglesowrth & Imms compresed

today I guess these have been replaced by Chapman’s The Insects: Structure and Function and Gullan & Cranston’s Outline of Entomology.  But of course outside the field of entomology who remembers Imms and Wigglesworth?  So we should, I think, be looking for entomologists whose influence has extended more widely;  a slightly tongue in cheek contender would be Thomas Moufet,  http://en.wikipedia.org/wiki/Thomas_Muffet who is possibly apocryphally, remembered for the nursery rhyme about his daughter Little Miss Muffett and more substantiated, for his compilation of the Theatre of Insects, but he was mainly a man of

Moufet book

medicine and more interested in spiders than insects in general.  A contender widely known outside the entomological world would be H W Bates, http://en.wikipedia.org/wiki/Henry_Walter_Bates#Taxonomy who is today remembered in the term Batesian

Henry Walter Bates

mimicry  http://en.wikipedia.org/wiki/Mimicry#Batesian ; as a former President of the Royal Entomological Society (1868-1869) I think that we can safely claim him as an entomologist.

Other entomologists that have had an influence  on the rest of the non-entomological world, albeit not widely known outside the biological or medical sciences are Fabre and his Lives of  various insects http://en.wikipedia.org/wiki/Jean-Henri_Fabre , Karl von Frisch http://en.wikipedia.org/wiki/Karl_von_Frisch for his work on honeybees, especially in deciphering the waggle-dance,  E B Ford for his work on ecological genetics and for inspiring Kettlewell’s work on Biston betularia,  http://en.wikipedia.org/wiki/E._B._Ford  and more recently Richard Southwood  http://en.wikipedia.org/wiki/Richard_Southwood   (Methods in Ecology) but initially a Hemipteran specialist and Miriam Rothschild  http://en.wikipedia.org/wiki/Miriam_Rothschild for her work on a range of entomological subjects but very famously for her work on fleas.

The acid test of course, is how many living entomologists the man or woman in the pub can bring to mind when asked, let alone those that have joined the Dead Entomologist’s Society. Perhaps it is the fate of entomologists to be largely overlooked, much like the small but highly important organisms we work on 😉

I would dearly love to hear your thoughts on which the most influential dead entomologists are.  I am well aware, that my list is very Euro- and UK-centric.  So let’s see some nominations from the rest of the world, suitably justified of course!

Post script

Getting my vote as a contender for an American entomologist of great influence, albeit British-born, would be Charles Riley, sometimes known as the Father of Biological Control http://en.wikipedia.org/wiki/Charles_Valentine_Riley , but then again, who outside the world of entomology has heard of him?


Filed under EntoNotes