Most insects can fly but a selected few are unable to do so . The few of them i.e the flightless insects are grouped under 4 orders which are : (1) order thysanurans (2) order collembola (3) order phasmida and (4) order diplura . The first order comprise of the silver fish funny enough it is an insect not a fish and it has no wing also it undergoes incomplete metamorphosis . The second order comprises of the springtails and the males deposit sperms called spermatophores on dead wood and drag the females across the spermatophores therefore we can say the males forcefully mate the females . The third order are the stick insects which look like dead wood . Finally the diplurans are wingles too and are the campodeids . Of all these flightless insects , the silverfish is microscopic as it cannot be seen with the naked eye . Similarities are that they can all be found in woody areas i.e under logs of wood to be precise . Th questions that comes to mind are : (1) Are they useful or harmful ? (2) Where can they be found ? . The answers are given below and they are : (1) Some are useful i.e orders 2 to 4 because they are detritivorous which means that they breakdown decaying substances into simple substances which plants absorb as nutrients you may say are microorganisms not responsible for this ? yes they are but these insects help to fasten the process since they feed on decay matter but the collembolas are very destructive because they feed on leaves of most crops e.g Bourletellia spp .(2) They are mostly found in woody areas under logs of wood but the collembollas are cosmopolitan i.e they can be found everywhere on land even in icy areas like the arctic region .