The combination in Mantidae of voracious and destructive instincts with helpless and inert attitudes gives rise to the idea that these latter are adopted for the purpose of deceiving the living prey and of thus more easily obtaining the means of subsistence. {251}It appears, however, more probable that the helpless attitudes have no such origin, but are due to the structure and form of the creature. The front legs being wonderfully well formed for raptorial purposes, have no capacity for locomotion or for supporting the Insect in the usual manner, so that the body has to be borne by the hinder two pairs of legs; at the same time the raptorial pair of limbs—which, it will be recollected, are of great size and attached to the anterior part of an unusually long prothorax—have to be held in such a position as will not derange the equilibrium maintained by the posterior part of the body; moreover, these large raptorial legs are entirely exserted, and have no trace of any articulatory cavity that might act as a mechanical aid to their support. Thus they could not be held extended without great muscular exhaustion; hence we can well believe that the sedentary and helpless attitudes of the creature are not the results of any guile. A _Mantis_ has been recorded as bearing a close resemblance to a Phasmid of the genus _Bacillus_ and having only small front legs; it was suggested by Bates[179] that the Mantis would probably be found to feed on the _Bacillus_. Though the case is of considerable interest, no further information about it has been obtained. [Illustration: FIG. 141.—_Mantoida luteola_ Westw., male. Santarem.] The simplest forms of the family are found in the groups Amorphoscelides and Orthoderides. From our figure of one of these (Fig. 141, _Mantoida luteola_ ♂), it will be seen that the peculiarities of the family can scarcely be detected, the raptorial legs being very little developed and the prothorax short. The sexes, too, differ but little in these simple forms. Most of them are very rare in collections, but Wood-Mason states[180] that _Amorphoscelis annulicornis_ is frequently found about Calcutta on the trunks of trees, to the bark of which it is so similar that it is only discovered with difficulty. In its rapid movements it resembles the cockroaches or _Machilis_, more than it does the more differentiated forms of its own group. {252}In the genus _Pyrgomantis_ (Fig. 142, _P. singularis_, female) the male has the tegmina and wings of normal size, while in the female they are rudimentary. [Illustration: FIG. 142.—_Pyrgomantis singularis_, female. S. Africa. (After Westwood.)] [Illustration: FIG. 143.—Outline of _Chaeradodis cancellata_ ♀, nymph. (After Wood-Mason.)]