The flies from the forest

Geetha Iyer

This is the final article in the Nature Watch series. During my years as a biology teacher, I have often felt incomplete and disappointed with myself for not being able to identify several plants, insects, birds and other creatures we came across on our nature walks or outdoor biology classes. In the 1970s-90s, there were not as many field guides or books available as there are today. One was dependent on the few resource persons or people from WWF-India for information and identification. Most books on Natural History found in school libraries were about European species. It was tough to get help or information. I would forever be chasing resource people in order to become familiar with India’s biodiversity and Natural History. I also lost no opportunity to join as many field trips and nature camps to further my knowledge. But such luxuries – and believe me they are luxuries for a teacher – are not possible for everyone. The Nature series was my attempt at sharing what I had learned, so teachers would not have to run from pillar to post for knowledge.

When I retired from active teaching in 2005, and started working with teachers, I found that in many schools – especially those that were located in the smaller districts of various states, from Gujarat to Kerala, Hyderabad to Lucknow, or some even from Delhi, Mumbai and Chennai – the story of European encyclopaedia being the source of information for biology teachers was still prevalent. By the year 2000, there were some fine books and newsletters on Indian Biodiversity published and available. Thanks to Dr Madhav Gadgil’s Landscape programme, Resonance regularly published some fine articles on Natural History. Yet it had not reached very many teachers. It was also the time when Teacher Plus had moved from its tabloid format to a magazine in colour. What better way to reach out to a large number of teachers than through a magazine for teachers!

Teacher Plus was kind enough to give me space to write about the magnificent biodiversity that India has. A lot more can be written but I tried to stay with those that teachers and students can see easily or ones that a teacher can use in a biology class. Teachers needed to move away from cockroaches, mosquitoes, frogs and rats in their biology classes and instead expose children to the diversity in their neighbourhood. The series was an attempt to make learning about biodiversity more contextual. It has been a happy writing experience for me, but I have often wondered whether it was the same for you, the readers – was it useful? I have had some very positive (but limited in number) feedback about the articles, but I have never stopped wondering whether it was useful at all!

As I write the last one in this series, I have taken the liberty to move away from insects of urban areas. The insects in this article are those that reside deep inside the forests, preying on the sap sucking insects and protecting trees; what a biology teacher would categorize as “useful insects”. Occasionally, you may spot one of them, namely the lacewing, in areas that have a lot of greenery, but the scorpion fly, the dobson fly, and the mantid fly are unlikely to be seen unless you are in a wooded area or a forest. Due to space constraints, the description here is brief but you can read more about their fascinating life in my book¹ (reviewed in Teacher Plus, November 2016 issue).

Net-winged insects
Among the 24 orders of insects is one called the Neuroptera comprising the net-winged insects. As the name implies, their wings are like nets covering, rather, draping their abdomen to present a very elegant appearance. Add to it the beautiful colours some of them sport, they are sure to draw admiration from anyone who looks at them. The most familiar neuropteran is perhaps the antlion which look like the damselfly. Watching an antlion larva capture ants – in the cone like pits they make – can be a very interesting nature club activity. But the insects I describe here for you are the lesser known lacewings and mantidfly. Also described are the scorpion fly and the dobsonfly that were earlier classified under Neuroptera but now are grouped under the Order Mecoptera and Megaloptera respectively.

Lacewing: As the name implies its wings are transparent and appear like a miniature fish net covering their abdomen. The most common one is green in colour but there are species that come in different shades of pink, brown, yellow and of course green. Lacewings lay stalked-eggs on the underside of leaves. The larvae hatch, climb down the stalk to start feeding. They are voracious eaters and can clean out several aphids, mealy bugs several times faster than a ladybird beetle. The larvae are called ‘aphid-lions’ because of their large, curved mandibles. The lacewing males have courtship songs to attract the females. An unusual feature is the eggs – they are laid at the end of a stalk.

They have been introduced as biocontrol agents in some countries to replace harmful pesticides. We are aware of only ladybird beetles as biocontrol agents but a lacewing larva can eat nearly twenty times more than the ladybird beetle larvae and are effective controllers of populations of most agricultural pests such as white fly, mites, thrips, leafhoppers in addition to aphids and mealy bugs.

For those who are interested in Taxonomy, it’s useful to remember that insects with the common name lacewings do not all belong to the family Chrysopidae (green lacewings) but may be classified in different families.

Mantid fly: Called also as mantispids or mantid lacewings, this family of insects also belongs to the Order Neuroptera. Like lacewings, these insects too are draped by net-like wings on their abdomen. At first glance, you are most likely to mistake them for a praying mantis. A second look will make you wonder if it’s not a paper wasp? These are unusually shaped insects. Its elongated prothorax, head with large bulging eyes and raptorial legs make it look like a mantis. The brown coloured body and wings have a pattern resembling the commonly seen paper wasp. Some of them are tiny, and you may well miss them if you are not very observant. There are a few that are bigger in size. The ones I have seen have not exceeded 30mm in length. While the adults prey on small insects, their larvae are spider egg predators and have developed various mechanisms to access the spider egg. Their life-history is quite fascinating. These are more common and diverse in the tropics than other parts of the world.

Scorpionfly: Scorpionfly belongs to the Order Mecoptera. As the name implies, some body features of this insect bear resemblance to a scorpion. Not all mecopterans are scorpionflies. Another prominent family of this order comprises insects that are called hanging flies. The males of scorpionflies have genitals that resemble the stinger of scorpions, hence the name. But their life history is quite unlike the scorpions. These flies feed on cadavers and are among the earliest to arrive at the site, hence these flies are of much importance in forensic science.

Dobsonfly: Along with fishflies and alderflies these insects belong to the Order Megaloptera. Megaloptera means ‘large wings’ and is quite indicative of the large wings these insects possess. The aquatic dobsonfly larvae found in streams are used by anglers for fishing. The male dobsonfly has a large pair of mandibles extending from its head giving one a feeling of an insect that is likely to bite violently. But that’s not so. These long curved mandibles are used to attract females. The competing males try to flip one another to establish their superiority in the hope of winning the mate.

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