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.