Antipredator Defense as a Limited Resource : Unequal Predation Risk and Broods of an Insect With Maternal Care

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More than two centuries ago, a Swedish scientist named Modeer described what appeared to be maternal behavior in the acanthosomatid shield bug Elasmucha grisea. He noted that the female did not fly away when an intruding object threatened her compact egg mass; instead, she remained steadfast and tilted her body towards the object (Tallamy). Unfortunately, this evidence, no matter how well documented, was not enough to convince countless people of the possibility of insects having parental instincts. The acknowledgement of parental behavior in insects was not a widely accepted idea for a number of years. Many people believed insects were too primitive to care for their young and that only when physical
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It seems obvious that parental antipredator behavior should benefit all offspring simultaneously. However, if the parents are unable to successfully defend all of their offspring all of the time, the risk of predation becomes unequally distributed. For example, broods that are relatively large often display a selfish herd effect, where the individuals closest to the outside edges of the aggregation are at a greater risk of predation than the individuals located near the middle. It seems reasonable for siblings to compete for the most protected or defensible locations, which also contributes to the unequal distribution of risk. The parent's ability to defend all offspring at once is also largely dependent on the spatial configuration of the brood: the farther an individual is from the parent, the greater their risk of predation. In the U. crassicornis, maternal protection is also influenced by signals produced by the offspring. The signaling, which consists of synchronous vibrational bursts, appears to be coordinated. This coordination would be expected if each individual benefited simultaneously from maternal defense. However, if the maternal defense does not benefit the entire brood at the same time, the synchronized signaling may indicate another element of

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