ail, flashing red whip-like threads from its ends and flourishing them in the air (Fig. 1 – puss moth caterpillar). Finally, when the attack persists, the caterpillar forcibly ejects from its prothoracic gland a burning, colorless fluid containing 40% formic acid.
             Insects face a nearly constant threat of death from predators. Under such severe pressure, selection greatly favours those individuals who are able to reduce the risk of attack or injury most successfully while simultaneously sustaining the ability of perform other necessary life functions.
             Insect defense mechanisms involve a widespread convergence of various structural and behavioural adaptations. Such adaptations include hiding (of which various forms will be discussed), mimicry, mechanical defence, and chemical defence. Social insects also incur methods of collective group defences to ward off attacks. Loosely, the structural adaptations can be thought of as passive defence, whereas the behavioural adaptations may represent more active forms of defence.
             Undoubtedly, the most widespread method by which insects evade potential threats is through crypsis. Crypsis is the first form of passive defence and can take two forms in nature: background imitation or imitation of inedible neutral objects. Crypsis involves at least shape, colour, and colour pattern, but may also involve scent and sound imitation. This first form of crypsis, or camouflage, can be utilized in various ways. Firstly, insects may resemble a uniform coloured background or a patterned background. To be maximally camouflaged against either of these backgrounds, cryptic individuals need to deal with the problem of contours. This may be accomplished through disruptive coloration, a visual breaking of the insect's outline so that it appears to fade into the background (Fig. 2 – a carpet moth hidden on bark). Insects can also minimize contours by reducing any shadows produced...