188 MODERN CLASSIFICATION OF INSECTS. 

With a view to illustrate this subject more completely than has 
hitherto been done, I have given in fig. 80. a series of illustrations of 
the structure of the anterior and posterior legs of various species, 
whose economy has been discovered, and which it will be seen vary 
very considerably inter se, so as to have led Saint Fargeau to adopt 
the theory above noticed. I have also added figures of the mandibles 
of the different species in question, although the precise share which 
these organs take in the economy of the several insects has not been 
clearly noticed: the figures marked t 1 represent the anterior tibia 
and tarsus, t 3 the posterior tibia, and m the mandible /%g. 80. 1. 
represents these details in Crabro cephalotes 9, a wood-boring spe- 
cies; and in which the anterior tarsi are but very slightly armed with 
short thin spines: the hind tibiz are very strong and rough, with short 
thick spines. /%g. 80. 2. represents the same ‘parts in Pemphredon 
unicolor, also a wood boring species, having the anterior tarsi very 
slightly spined, but furnished on one side with long curved hairs ; 
the hind tibiz have only four minute spines on the margin. //7g. 80. 3. 
are from Gorytes mystaceus; the fore legs being still less spined, 
and the hind tibiz quite simple. This species I have selected, as 
being that which led Saint Fargeau to establish his theory, consider- 
ing it a parasite. It is, however, as Mr. Shuckard and myself have 
discovered, a predatory species; and that gentleman states that he has 
seen it enter a sand bank with its prey. Mellinus arvensis (fig. 80. 4.) 
has stronger and longer spines to the fore tarsi, and the hind tibia 
has a marginal row of short spines. This is common in sandy dis- 
tricts, its prey consisting of Diptera; but it has not been observed 
to burrow, unless indeed Réaumur’s figure, subsequently noticed, be 
intended for it. /%g. 80. 5. represents a more decidedly fossorial 
