270 Mr. Shuckard's Monograph of the Dorylidae, 



to them in the description of insects*. The Rev. Mr. Kirby said, 

 many years ago, — " The head and its organs are in some degree ana- 

 logous to the root in plants, for they collect and absorb the nutri- 

 ment ; the truncus may be looked upon as representing the stem, the 

 limbs the branches, the wings the leaves, the abdomen as a kind of 

 calyx, including the fructification. Therefore the great command, 

 * increase and multiply,' will direct us to those parts which con- 

 stitute the essence of an insect." He next says in continuation, 

 " but these, if it were possible, it would be improper to use for 

 characters.*' I introduce them here certainly not as characters, but 

 in confirmation of less tangible characters, thus proving the efliciency 

 of the latter, and as a small contribution to the description of the 

 comparative structure of these organs in insects, which comparative 

 anatomists may not always or even frequently have the opportunity 

 of examining. 



In Dorylus helvolus this organ consists of two large fornicate valves 

 (the external sheath of the penis. Burnt.) which are fringed at their 

 apex ; within the fornix, and springing from the centre of its base, 

 there is an elongate linear process (the penis) deeply longitudinally 

 channeled both above and beneath, and which extends to the apex 

 of the valves opposite their central division : this division reaches 

 nearly to their base, where these valves have a common origin, and 

 this base forms on each side beneath a convex return, with which an 

 elongate compressed spine (the inner sheath) articulates, having a 

 vertical motion ; and these spines curve upwards on each side of the 

 central canaliculated process near its base, where it is also articu- 

 lated. At the extreme base of this complex organ, and articulating 

 with it beneath, there is a horizontal flat linear plate deeply furcate 

 at its apex, the furcation half the length of the plate, which also ex- 

 tends to the apex of the two large superior lateral lobated valves. 



It is a circumstance worthy of remark, that wherever I have had 

 the opportunity of examining and comparing several individuals of 

 a species throughout the family, I have found so great a uniformity 

 of size that I have not detected a difference of half a line even among 

 the larger ones. Thus although the characters that separate them 

 are sometimes very obscure, and without patient examination elude 

 discovery, my experience seems to support an opinion that wherever 

 great differences of size are found between specimens of these genera, 

 the presumption is, that characters exist which will individualize 

 them, although too recondite for instant detection, yet so tangible 

 when found as not to admit of the least doubt of their specific value, 

 * Monog. Ap. Angliae, vol. i. p. 39. 1802. 



