by Kunal Ankola
Beautiful coloration, unique behaviour and fascinating lifestyles are among the qualities we admire about butterflies. When it comes to behaviour, there are many aspects of butterflies that are often seen but mostly ignored. Puddling is one of the behaviours observed in butterflies through which they acquire mineral nutrients from different sources. Puddling in butterflies often referred to as mud puddling, is actually a drinking process in which the imagoes (adult butterflies) drink dissolved minerals and nutrients from various sources. The specialised mouth part used for drinking is called a proboscis, which is actually a straw-like structure. Generally, puddling is a characteristic behaviour seen in lepidopterans (butterflies and moths) but is also found in a few other insects.
Insect physiology is often under the influence of various biotic and abiotic factors. In butterflies, inorganic minerals play a vital role as a dietary component essential for the regulation of most of their physiological processes. However, these minerals are not sufficiently available in the leaves of their host plants, on which the larvae feed. Generally, feeding in butterflies is not just confined to their larval period. The adults often feed on nectar and puddle over various sources to compensate for their nutritional lacunae. Puddling, on the other hand, serves solely to make up for the lack of minerals they cannot obtain during their larval stage. The inorganic minerals derived from puddling play a significant role in regulating neuromuscular events and thus aiding in their flight mechanism. In addition, sodium that the male imago receives during puddling is transferred to females at the time of mating as a “nuptial gift” through spermatophores that further help females in oviposition.
Where to puddle:
There are no such specific places where butterflies puddle, but they are more attracted to mineral-rich sources including wet soil, clay and mud. In addition to this, most of the butterflies are often seen puddling over other sources including animal dung excreta, carrion, rotting plant matter, fruits etc. It is very common to witness butterflies attracted to human sweat, which is a rich source of salts and sugar. There are several cases of butterflies puddling over sweaty human bodies (hands, face, etc.) and also on human objects including footwear containing sweat droplets.
Physiological phenomenon or competitive behaviour:
Though puddling supports various physiological activities including ovipositioning and flight mechanism, it also has a behavioural relevance in the life history of butterflies. The adults puddle not only to compensate for their nutritional lacunae but also to boost their chances of mating. Recent research on the butterfly Papilio polites revealed that the young males compete with one another and puddle for a longer period of time to attract females. The females prefer those males who puddle more to gain a sufficient amount of minerals. However, excessive puddling can cause excess fluid that has accumulated in the digestive tract to be expelled through the cloaca which is a common opening for the digestive and reproductive tract.
The frequency of puddling in young males, on the other hand, is strongly influenced by environmental temperature, which further determines their puddling competition. The puddling activity increases in young males at an optimum temperature ranging from 26°C to 28°C. However, the urge to puddle decreases in males when exposed to temperatures other than the optimal range. Alternatively, the fecundity and longevity of imagoes remain unaffected by the frequency of puddling activity.
Dr. Kunal Ankola, Guest Faculty and Research Scholar, Department of Studies in Sericulture, Manasa Gangothri, University of Mysore, Mysuru.
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