Interview with a social insect scientist: Yoshihiro Y Yamada

You can read Yoshihiro’s recent research article about the influence of photoperiods on caste fate of paper wasps here.

IS: Who are you, and what do you do?

My name is Yoshihiro Y Yamada. I am a professor emeritus at Mie University, Japan: I retired at the end of March 2020. I have been studying the behavioral ecology of parasitoids and host-parasitoid population dynamics over 40 years, and I started to study the social biology of paper wasps around 2005. I will continue to study the social biology of paper wasps as long as I am healthy.

Yoshihiro Y Yamada in Zen meditation

IS: How did you develop an interest in your research?

The late Dr. Matsuura, former professor of Insect Ecology Lab at Mie University, was an expert in the biology of Polistinae (paper wasps) and Vespinae (hornets). I had often talked with him and his students, and I became interested in paper wasps and had several questions about the biology of paper wasps. I am now exploring answers to these questions with my coworker Dr. Yoshimura.

IS: What is your favorite social insect, and why?

Paper wasps. I have observed them for so many years that I feel as if I could understand how they feel, what they want, and what they are thinking about.

Nest of Polistes jokahamae. Photo: Hideto Yoshimura

IS: What is the best moment/discovery in your research so far? What made it so memorable?

Regarding the field of the social biology of paper wasps, our best discovery is that photoperiod is an important factor for determination of caste fate in the paper wasp Polistes jokahamae (Yoshimura and Yamada 2018, 2021). Bohm (1972) suggested that that photoperiod could influence determination of caste fate in P. metricus, but no researchers have studied the effects of photoperiod in paper wasps since Bohm. Many researchers appear to disagree with the importance of photoperiod. Our preliminary experiments suggest that photoperiod influences determination of caste fate in several other temperate paper wasps. We are sure that most temperate paper wasps use photoperiod as a cue for determination of caste fate.

IS: Do you teach or do outreach/science communication? How do you incorporate your research into these areas?

I sometime teach the biology of bees and wasps, including current hot topics and our recent works to high school students and adults interested in the development of science.

IS: What do you think are some of the important current questions in social insect research, and what’s essential for future research?

Regarding social wasps, mechanisms for caste-fate determination and for establishment and maintenance of queen royalty are important themes for current studies. Comparative studies of several species are essential for future research.  In addition, it is important to keep in mind that several factors are involved in the mechanisms.

IS: What research questions generate the biggest debate in social insect research at the moment?

Regarding social wasps, do adults emerge with a caste-related bias? In other words, to what degree does preimaginal caste determination occur? Answering this question is critical for understanding the origin of eusociality and transition from primitive to advanced eusociality.

Hideto Yoshimura, smiling, with a large nest in his hand

IS: What is the last book you read? Would you recommend it? Why or why not?

Pheromones and Animal Behavior: Chemical Signals and Signatures, by Tristram D. Wyatt (2014). I strongly recommend students interested in pheromone communication in animals including insects and vertebrates. The book is quite readable, particularly for people without special knowledge of chemistry. Researchers also might get some hints from the book.

IS: Outside of science, what are your favorite activities, hobbies, or sports?

Gardening. I am trying to make a garden attractive to animals. When my wife and I have breakfast or tea while watching insects, birds and cats visiting our garden, we have a peaceful and wonderful time.

IS: How do you keep going when things get tough?

I go to an onsen (hot spring) area for relaxation. In addition, I practice Zen meditation.

IS: If you were to go live on an uninhabited island and could only bring three things, what would you bring? Why?

My wife Tomoko, survival kit including fishing equipment, and sake. I cannot imagine the world without them.

Hideto Yoshiura collecting a nest

IS: Who do you think has had the most considerable influence on your science career?

Dr. Tomo Royama and his book, Analytical Population Dynamics: I managed to understand the essence of population dynamics through him and the book.  I hear that his new book will be published soon.  I am looking forward to reading it.

IS: What advice would you give to someone hoping to be a social insect researcher in the future?

I hope that young researchers will have their own questions and explore them, not just follow current hot topics.

IS: What is your favorite place science has taken you?

Campus and experimental farm and forest of Mie University and mountain and hill areas in Mie prefecture: many insects, including wasps and bees, are found in the areas.

IS: If you had unlimited funds to conduct whatever research you wanted, where would you go and what would you investigate?

I would like to go to subtropical and tropical areas and explore the biology of paper wasps.

How best to sample termites – or the importance of loo rolls

By Paul Eggleton

Based on research for the review paper, in press: “A.B. Davies, C.L. Parr and P. Eggleton. A global review of termite sampling methods. Insectes Sociaux.”

The three co-authors (from left to right: Kate Parr, Andrew Davies and Paul Eggleton) giving out a certificate to a student at a termite identification course in South Africa.

Social insects have always been difficult to sample. Do we count the colonies or the individuals; the organism or the superorganism? The bumble bees buzzing in your garden, are they really separate beings or just flying bits of an individual that is, in fact, much bigger?  But at least bees and wasps fly, so can be sampled using nets or traps that catch insects on the wing, and ants are usually running around on the ground, so can be sampled using traps that they fall into. When it comes to termites, only the reproductive caste flies, and all the wingless individuals, the soldiers and the workers are underground in the soil or hidden in dead wood.  This wouldn’t matter if termites were rare and unimportant things, but, in fact, they make up a huge amount of global animal biomass and are known to be extremely important for ecological processes. This poses a real problem for termite quantitative sampling, which is vital if we are to understand the role of termites in ecosystems. We discuss this in our recent paper, where we review termite sampling methods.

Termites are found predominantly in the tropics, in areas that traditionally have been hard to access. They are at their most abundant in tropical rain forests and savannas, places that are hot and often extremely humid.

Soldiers of Macrotermes bellicosus on the surface of dead wood, Kenya

The most obvious way to sample termites is to extract them from their mounds or nests. Termite mounds are easy to find, and although some of them may have a hard outer wall, are easy to get into. However, this will not give an accurate estimate of the species present as only a small fraction of termites have conspicuous mounds. Most colonies live underground, with no visible external structures. In fact, here are really only two ways to sample termites effectively – sampling them directly by picking them out of where they live or attracting them with baits.

A toilet roll out in the field for monitoring porposes (Sabah, Malaysia)

In dry areas, such as dry savannas and deserts, toilet roll baits are the most effective way of assessing termite diversity and activity. They are essentially cellulose, which is like a chocolate snack for a termite. In fact, termites generally gobble up the outer tissue rapidly and leave the inner roll behind. The termites can be taken directly out of the roll and the state of the roll can be assessed for termite activity. This works because in drier areas there is generally only wood feeders and there are few termites that can be extracted from the dry, hard soil. The main problem is that they are attractive to larger animals, particularly people, and they can, fairly often, be removed or disturbed by pigs or dogs. Toilet rolls are a major part of my group’s field work tools, and shopkeepers are often surprised when you buy their whole stock of loo roll in one go. They must wonder why on earth we need so much!

Toilet rolls waiting to be deployed (Sabah, Malaysia).

In wetter areas the problem there is the opposite – there are too many termites that live in the soil and are not attracted to cellulose baits. Soil-feeding termites become increasingly important as the environment becomes wetter and more stable. They feed directly on the soil and are important elements of the nitrogen cycle. Most of these termites are found living underground, with no obvious nest structures and so digging up the soil is the only way to find them. This is also related to the habitat complexity, as soil feeding termites are predominantly found in tropical rainforest, which show great horizontal and vertical variation, across the ground and up the trees. This means there are more places to search in tropical rain forests than in drier savannas – the soil, in mounds and nests, in and on trees, in dead wood, in the soil, and in the buttress roots of trees.

The authors’ student Fidele, sampling termites using the ‘transect method’ in a Gabonese rainforest.

We recommend some standardised methods in the paper, and essentially propose a standard method, and modifications of it that were developed in the late 90s, by my colleague, David Jones and me.  This involves intensive searching of a 100 m x 2 m “transect”, and takes, a rather gruelling, 20 person hours to complete.  In areas, such as wet savanna, where there are fewer trees, and many fewer places to search, we have reduced this to a fraction of this time, while still retaining the same general principles.

There are some habitats where sampling is harder. Grasslands tend to have surface foraging grass-feeding species that do not come to toilet roll baits and have unpredictable foraging patterns, usually at night. Sampling termites using a head torch is probably a step too far for even the most dedicated termitologist.