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INSECTS WITH PARENTAL INSTINCTS



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 1997). 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 conditions became extremely severe were insects capable of expressing paternal abilities. The traditional view of maternal care is that it is an exceptional and relatively recent evolutionary leap forward (Tallamy 1997).

Fortunately, the assumptions made about maternal care in insects do not have to be accepted or rejected based only on faith or an educated guess; today it is possible for these predictions to be empirically tested so that the data may be recorded and analyzed. The following experiment is just one example of the various ways in which ideas regarding insects and maternal care may be effectively evaluated.

Reginald B. Cocroft, of the Neurobiology and Behavior Department at Cornell University in Ithaca, New York, researched insects known as Umbonia crassicornis, or the thornbug treehopper. U. crassicornis offspring thrive in large aggregations on the often exposed stems of host-plants. These offspring are incredibly vulnerable, making them easy targets and subject to intense predation by vespid wasps (Pseudopolybia compressa). Maternal defense is their primary means of protection as well as the primary source of potential conflict among broods, expressed in the way that siblings compete for a disproportionate share of limited resources (Cocroft 2002).

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