Itch created by rush of histamine
Sandfly, or mosquito, bites itch and itch heaps! But why? And by that I mean what is the evolutionary advantage to the sandfly, or mosquito, in making its victim suffer so much? Associate Professor Kirk Hamilton, a physiologist from the University of Otago, responded.
Spring is coming, and we will spend more time outside, perhaps visit our favourite haunts on the West Coast. What do we encounter which we had forgotten about during winter: the dreaded sandfly (namu)! Of course, we are familiar with Sandfly Point in Fiordland opposed to Sandfly Bay in Otago. One has sandflies, while the other has sand that flies.
In May 1773, visiting Fiordland's Dusky Sound, Captain James Cook noted ‘‘the most mischievous animal here is the small black sandfly which are exceedingly numerous . . . wherever they light they cause swelling and such intolerable itching that it is not possible to refrain from scratching and at last ends in ulcers’’.
Sandflies date back more than 200 million years, and it is thought that they were bloodfeeders even back then.
Nowadays there are more than 800 species of sandflies, but only 18 native in New Zealand. Most feed on vegetable fluid, flower nectar, honey dew. However, some have developed a passion for blood from vertebrates including seals, penguins and other birds, domesticated animals and even humans. The species which is found in the South, and especially in the West Coast, is Austrosimulium ungulatum.
The sandfly receives a reproductive, hence evolutionary, advantage by biting us and we feel pain. They are attracted to us by sweat, carbon dioxide, pheromones, and dark colours. Only the female bites, while the males appear to be vegetarians. After mating, the females search for a source of blood to aid in the production of eggs. When biting, it uses its mouth and claws to tear through the skin to gain access to blood. Its saliva contains anticoagulants which prevent blood clotting, and agglutinins which prepares the blood to be digested by the sandfly. It has been demonstrated that females, who have a food source of blood, produce more eggs than females who do not. Therefore, sandflies feeding on blood increases the number of progeny, and helps to maintain the species.
Why do bites itch? Responding to the sandfly's saliva, the body quickly releases histamine, resulting in movement of fluid to the wound site to dilute the saliva. This rush of excess fluid leads to swelling and produces the itch response.
When my wife and I go hiking I hardly get bitten, but apparently she is a sandflymagnet, and attests that it is because she is so sweet. But, what does that say about me?
The remarkable Major Thomas Broun (18381919) described 4323 (nominal) New Zealand species of beetles, of which 3538 were new to science.
Unfortunately, only 37 of his published descriptions were illustrated, and most diagnoses were so brief and rudimentary that few of his species can be identified from his descriptions alone. Indeed, New Zealand beetles described by Broun cannot be identified without seeing his type specimens in person.
In fairness to Broun, it should be noted that his descriptions were similar to those of other worldleading beetle specialists of his time.
Which brings us, again, to the clouds hanging over Britain’s Natural History Museum, because that’s where Major Broun’s collection resides.
A holotype, or type specimen, is the single specimen chosen for the designation and description of a new species. The Natural History Museum (NHM), in London, is of huge significance to New Zealand entomology, the study of insects, because of the large number of holotypes (and other primary type specimens) of New Zealand insects it contains.
This situation has both good and bad implications for science. A significant unfavourable outcome is that, of the thousands of type specimens of New Zealand insects housed in NHM, many of the species they represent cannot be recognised within New
Zealand from the original published descriptions.
Beetles, which comprise 53% of described New Zealand insects, provide a good example of the problem.
Major Broun’s collection of New Zealand beetles was sent to the NHM in 1922, despite heated protests from New Zealand scientists at the time. Broun had held the paid position of New Zealand government entomologist with the New Zealand Department of Agriculture for 17 years, in the latter part of his life.
Since 1922, New Zealand beetle specialists wishing to revise families of New Zealand beetles have had to borrow Broun’s types (syntypes) four at a time from the NHM, or visit the
If you start drinking more, or quit drinking, your cancer risk may change too, according to a study of South Korean adults.
They found those who increased
Captain (later Major) Thomas Broun, father of New Zealand beetle specialists.
institution. This resulted in New Zealand beetle specialists not knowing the New Zealand beetle fauna adequately, which would not be the case if Broun’s collection had remained in New Zealand. Even when I revised some families of New Zealand solitary wasps, I had to borrow type specimens a few at a time from the NHM.
In the 1980s, Prof Howard E Evans, the USbased world expert on solitary wasps such as the Pompilidae family, sent his entire collection of Pompilidae to the NHM, because the collections there were unrivalled worldwide, but not so well represented from North and South America. Evans hoped that NHM Hymenoptera curator Mick Day would work out the difficulties of the family on a world basis, using Evans’ own large collection as well as the NHM collection. Evans was upset when Day was suddenly let go in 1990 and wrote to me about the situation.
To the dismay of many, the NHM is now is planning to further dismantle its worldleading role and relinquish its expertise by scattering staff and diluting its focus.
The main advantage of having world collections in the NHM is their alcohol consumption had a higher risk for alcoholrelated cancers than those who kept their alcohol consumption the same.
The risk was also reduced by quitting or sustained cuts to consumption. — JAMA Network
that a specialist employee of the NHM can study those collections, which are sufficiently comprehensive for them to discern and work out the world classification for a family of organisms. This requires many taxonomists in the NHM.
The NHM is an internationally renowned institution with world collections and only makes sense if it continues to undertake worldwide systematic research based on these collections. If this ceases to happen, perhaps the New Zealand Government should request the return of the Thomas Broun collection. Much of
Broun’s material was provided by a nationwide bevy of New Zealand beetle buffs and collectors, who sent their specimens to him for identification and description.
Broun’s work on New Zealand beetles was a truly extraordinary achievement, including the volumes of his Manual of the New Zealand Coleoptera.
Had his collection remained in New Zealand, where local entomologists could have freely gained easy access to it, then Broun, as ‘‘father of New Zealand Coleopterology’’ (the study of beetles), would have sired a healthy child indeed.