Life isn’t
always fair. Some individuals are simply born more attractive than others. In
most cases the females are the choosy ones, whereas males will try to mate as
much as possible. So being unattractive poses the largest problems for males.
In many species, males will present the female with a gift (food), because,
while she is eating she doesn’t mind having sex. However, the amount of food
given is not equal between males. In the scorpionfly, unattractive males might
not get a female quickly, but once they do, they sure know how to keep her
around for a while!
The scorpionfly
The
scorpionfly is aptly named scorpionfly due to the scorpion-like tail of the
males, which they use to grab hold of the female during intercourse (see
pictures below). They might look a bit terrifying to some people, but they feed
on other insects and are not dangerous to us. Male scorpionflies “call” females
by emitting long-range pheromones. Once they have attracted a female, they
engage in long premating associations characterized by male wing and abdominal
movements with sometimes brief genital contact (a sort of dancing). Finally,
the male produces a salivary mass (spitball) which initiates copulation.
The
female will eat the spitball, once she has finished the spitball, she’ll fly
away. So the bigger the spitball, the longer the mating!
Take your time
This sounds
all simple enough. However, scientific research to a particular species of
scorpionfly (Panorpa cognata) showed
that it is not as straight forward as that. A scientist by the name of Leif
Engqvist found some interesting things by studying these critters. He basically
started by catching scorpionflies and then staring at them for more than 6
hours a day. He found that while some males almost immediately jump the female
when she arrives, others dance around with her for more than 6 hours.
So why would
some wait so long before closing the deal while others will close the deal
almost immediately? Leif found that females are more likely to mate when the
dance takes longer (Engqvist&Sauer 2002). As the production of the
salivary mass (spitball) takes energy, it is costly to waist when the female
leaves without mating.
So if you only have one spitball, you better make sure
that when you give it to a female she will be willing to mate! However, some
males are in much better condition and are able to produce multiple spitballs,
so they do not mind taking the risk that she flies away before mating.
The casanova of scorpionflies
Not all
males are equally attractive. When a male starts “calling” to attract a female,
it can take some time before a female arrives. However, the time it takes for a
female to arrive varies greatly! Some males attract a female within a couple of
minutes, but some take 6 hours before they are able to attract a female
(Engqvist 2011). Furthermore, the time it takes a male to attract a female is
heritable. Which means that some males are simply more attractive than others.
The
attractive males have larger salivary glands (spitball producing glands).
However, the more attractive males produce smaller spitballs, which means they
can only have a quickie (remember, the female leaves as soon as she finished
eating the spitball). If they have such large glands, why would they only
produce small spitballs while the unattractive males with small glands produce
large spitballs?
This is likely because attractive males can attract another
female quickly and by producing many small spitballs they can have sex with
lots of females. The unattractive male is less likely to attract another female
anytime soon, so once he does manage to attract one, he tries his best to make
it count. He dances around with her for hours and gives her all the spitball he
can come up with.
Female scorpionflies mate with multiple males, so not all her
eggs are fertilized by the same male. Attractive males fertilize a few eggs
with many females, but unattractive males do all they can to mate as long as
possible with one female and try to fertilize as many eggs as possible with
her.
So which tactic will work best? It will depend on the quality and attractiveness of the male. Attractive males might get the most offspring by slutting around as much as possible. Unattractive males can try, but will utterly fail and are better off when treating one girl right.
References:
1) Engqvist and Sauer (2002) Amorous scorpionflies: causes and consequences of the long pairing prelude of Panorpa cognata. Animal Behaviour 63: 667-675
2) Engqvist (2011) Male attractiveness is negatively genetically associated with investment in copulations. Behavioural Ecology 22(2): 345-349.
This article was originally published on Science Explained.
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