Hello steemians,  

In today’s nanoscience series I’ll be talking on the nature’s beauty in the development of hornet hives and how nanoscience is involved in it. 

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Everyone must have seen these and some of you also got stung by one of these, people usually misunderstood these with the bees. They are totally different from them, they are more aggressive and will attack in force, chasing the perceived threat for large distance (1).

These yellow hornets build communal nests by chewing the woods. There is one queen in the nest, who lays eggs while other are just workers, sometimes they build their nests underground also. Queen generally started building the first few blocks and then lays an egg into each one of them. During the time queen feeds on a high protein diet, the larva spins a silk cap covers the opening of the cells (2). The entire pupa is covered in silk and after the transformation to an adult, they will eat its way through the silk cap. Adults also secret the silk-like proteinaceous material which coats up the walls of hive (3).    [Image Source]

In a finding it was observed that the temperature of the nest is uniform through the different regions. In a situation where the temperature outside the nest is 42°C and inside the nest is 29°C at a mere distance 5 cm from outside. This observation raises a question on the thermoregularity of these hives.

  The cells are covered by silk caps of pupae.  Source

The silk produced by the pupating larvae possesses inter alia, heat regulatory property – probably a sine qua non for the survival of hornet. On further study, it was found that silk produced by these hornets are enabling them to thermoregulate and have other electrical property.

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These are the scanning micrographic images of silk strings intercrossing between sheets of various dimensions, shapes and the cross-section of a single silk fibre.

These nano sized silk fibers give them several properties; 

• Regulated temperature of hive at 29°C 
• Luminescence property of inner silk 
• Thermovoltaic, photovolataic property of silk

During the luminescence study, the silk was found to be anisotropic in that light reflected from the interior of the cap is different from exterior of the cap. If one project a light at 280nm wavelength to the exterior surface of cap the emission spectra will be obtained at 360nm. And when same was done on the interior surface, the emitted spectra was of same wavelength of 360nm but with almost double intensity. 

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Suggesting the reason, how the temperature is being regulated in these hives.

Thermoelectric phenomenon was observed in the dark, namely upon increase in temperature the current rose to several hundred nano Ampere (nA; in light, a photo-voltaic effect was observed involving voltage of several dozen millivolts (mV), with a sharp transition between the current and voltage during transition from darkness to light. A very high capacitance was also recorded, in range of milli farads (mF). 

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In summary, these hornet hives are just amazing construction by nature. The silk produced by these hornet are thermoregulator, photovoltaic and have luminescence property. The nano structured silk fibres are cross-linked to make such hives with such properties. This motivates the researchers to make incredible materials using such technique and to help mankind. Nature chooses the nanotechnology before we do.

References

Krishboim et. al., 2000 Silk produced by hornet: thermophotovoltaic properties - a review Comparative Biochemistry and Physiology 127, 1-20.

Sutherland et. al., 2011 The coiled coil silk of bees, Ants and Hornets, Biopolymers 97,6 ;446-454.

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Happy Reading :)

Vinamra