416 ON THE ORDERS 



is a reason founded on a most ingenious speculation of 

 M. Latreille, why we should believe his opinion of thenatu- 

 ral situation of the Strepsiptera to be less correct than 

 that of the distinguished naturalist, who first attempted to 

 decide with precision on their affinities. 



But to return : It may be remarked that while the thorax 

 of a Crustaceous animal has in reality ten feet, we find a 

 pair of these to disappear first in the males of such insects 

 as recede from the Crustaceous type. Thus the female 

 Nymphon is decapod like the Crustacea, while the male 

 has only four pairs of feet, like the Arachnida, — a mode of 

 change to which Nature appears to be partial in the struc- 

 ture of Annulose animals, when leaving" one form for another, 

 and of which I have given an instance on a smaller scale in 

 the change oi' the clypeus of the genus Anoplognat.hu s, 

 described in the first part of this volume. Savigny per- 

 ceived that the male Nymphon prepares us for the Arach- 

 nide form, in which we have never more than eight feet. 

 , M. Latreille indeed imagines that vestiges of a decapod 

 structure are visible even in some Arachnida, such as the 

 Scorpion, whose pectines he fancies to represent a pair of 

 feet or wings ; nor does he seem aware that his theory is 

 supported by the opinions which Redi and Amoreux 

 formed, on observing the use which the animal makes of 

 these processes in walking. But, however this may be, it 

 is very sure that the less perfectly organized animals of this 

 class lose still further a pair of feet and become hexapod, 

 thus preparing us for the apterous and parasitical Diptera, 

 which again are among the least perfect of the Haustel- 

 latu. The tendency, however, of an Annulose animal to 

 a decapod structure is soon again visible,- for at first we 

 have a minute pair of wings, as in Hippobosca, which af- 



