Millions of years of evolution has gifted this planet with astonishing diversity of life forms. Insects in particular, which make up three fourths of all the world’s animal and plant species, come in staggering sizes, shapes and forms. Every insect species boasts of possessing unique morphological adaptations whose design and engineering differ so starkly from others, that it is hard to believe that many of these adaptations often serve the same purpose.
Larva of a Ladybird or ladybug (Coccinellidae family). Phase contrast image at 5x magnification. Credit: Purva Variyar
Next time you see an insect, observe its mouthparts or proboscis. That will help you to discern whether it is a “chewer” or a “sucker”. Different insects have developed different modes of consuming their food with highly specialised mouthparts. Insects feed on wide variety of foods, be it nectar from flowers or blood of other animals. Their mouthparts have evolved over time to perfect the function of “eating” and fitting into very specific ecological niches.
Earliest insects known to science had mouthparts capable of only biting and chewing. Over millions of years, insect species with very specific food preferences and habits evolved and their mouthparts too metamorphosed into extremely specialised apparatuses. Today, insects can do more than just chew and bite. Some insects engage in chewing and lapping such as honeybees and wasps, while some others, like mosquitoes, resort to piercing and sucking, even sponging as seen in houseflies, and siphoning off food as exhibited by butterflies and moths!
This short photo story is a collection of some interesting images I made to reveal the intricate microarchitecture of mouthparts or proboscis of some insects, well preserved on slides, among the collection accessed at the University of Nottingham, UK. These images have been made using a DSLR camera mounted on a compound microscope.
A. Proboscis of a blowfly (Calliphoridae family)
Proboscis of a blow fly (Calliphoridae family). Phase contrast image at 5x magnification (above) and 10x magnification (below). Photo credit: Purva Variyar
The unique proboscis of a blowfly is intricately designed to maximise the function of solely feeding on liquid foods. This mop-like sucking device, as seen under a microscope and magnified five and ten times (below), is made of hollow tubes or pseudo-tracheae (so called because it resembles the breathing apparatus in insects called trachea).
Photo credit: Purva Variyar
The blowfly can digest food only in liquid form. It regurgitates digestive juices through the pores on the pseudo-tracheae to dissolve the food, liquefying it, which it then slurps at leisure.
B. Proboscis of a butterfly (Papilionoidea family)
Proboscis of a butterfly from the Papilionoidea family. Phase contrast image at 5x magnification. Photo credit: Purva Variyar
As an adult butterfly emerges from its pupal case, one of its first tasks is to assemble the tube-like probosics which initially comes split into two separate strands called galeae. The butterfly must assemble it to form a single, tubular proboscis. This slender, tubular structure looks more like a straw with a pointy beak at the end, and can be curled up and unfurled at will. A butterfly’s proboscis is built to reach inside flowers for nectar and even pierce fruits to drink juices. When not using its probiscis to feed, the butterfly will keep it coiled up and tucked away.
C. Proboscis of a Tsetse fly (Glossina palpalis)
Proboscis of a tsetse fly (Glossina palpalis). Phase contrast image at 5x magnification. Photo credit: Purva Variyar
Saved the most intriguing specimen for the last.
Armed and dreaded! A tsetse fly which is known to occur only in Africa is synonymous with being the harbinger of sleeping sickness, a life-threatening disease that it can transmit to humans. It also infects livestock with a similar disease called nagana. The Glossina palpalis species of the tsetse fly is a main carrier of the unicellular parasite Trypanosoma brucei , responsible for the sleeping sickness. The parasite undergoes development within the body of a tsetse fly, and a part of this development takes place within the chambers of its proboscis. The fly’s stout blood-sucking device is built to effortlessly pierce through the skin of its thick-skinned hosts such as the buffalo, antelope, rhino and even crocodile! A closer, microscopic look reveals a set of sharp teeth and rasps that sit inverted on a pair of moveable structures called labella at the tip of the proboscis (not visible in this image, unfortunately). The movement of the labella cause the teeth to further tear into the host’s skin!
About the author: Purva Variyar is a conservationist, science communicator and conservation writer. She works with the Wildlife Conservation Trust and has previously worked with Sanctuary Nature Foundation and The Gerry Martin Project.
Disclaimer: The author is associated with Wildlife Conservation Trust. The views and opinions expressed in the article are her own and do not necessarily reflect the views and opinions of Wildlife Conservation Trust.
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