​MANTIS-FLY, the name given to neuropterous insects of the family Mantispidae, related to the ant-lions, lace-wing flies, &c., and named from their superficial resemblance to a Mantis owing to the length of the prothorax and the shape and prehensorial nature of the anterior legs. The larva, at first campodeiform, makes its way into the egg-case of a spider or the nest of a wasp to feed upon the eggs or young. Subsequently it changes into a fat grub with short legs. When full grown it spins a silken cocoon in which the transformation into the pupa is effected. The latter escapes from its double case before moulting into the mature insect.