BRITISH CHRYSIDID.E. 157 



which I consider as solely mechanical, for it has no true aculeus, 

 a necessary condition of which is, that it should likewise instil 

 a poison; but no poison-secreting organs have yet been detected 

 in them, nor have I ever understood that the puncture has pro- 

 duced inflammation. They are supposed to be parasites — 

 many, to all appearance, upon species of the genus Odynerus, 

 and some upon Osmia bicornis, Halicti, and Andrence. But 

 little is known of their history. Dahlbom says, their larvae are 

 apods, and subvermiform. In hot, sunny, sandy places, they 

 are to be observed running and flying with agility, and in con- 

 stant motion, investigating every aperture or crevice they meet 

 with. They are also found in numbers upon palings, posts, 

 the trunks of trees, and the leaves of plants, but less frequently 

 in the latter situation, and never but in the sunshine. But 

 their habits vary as much as their habit, and did we know their 

 history thoroughly we should, I dare say, find that they differ as 

 much throughout their developments as when arrived at their 

 perfect state, which will necessarily be adapted to their respec- 

 tive functions. But, not to weary the reader with hypotheses, 

 I will give a short synopsis of the external characters which 

 separate them into their several genera. But I must premise 

 that they are, in the majority of species, of a tolerable size ; 

 and I have never observed, even amongst their minims, 

 one less than a line in length, nor quite so small ; and their 

 colours are more or less metallic, in which copper, gold, steel, 

 and brass, vie with each other in refulgency ; but retournons 

 a nos moutons. 



A. Thorax narrowed in front : abdomen lanceolate, not 



convolvent I. Cleptes. 



B. Thorax not narrowed in front, and truncated at both 



extremities : abdomen concavo-convex, con- 

 volvent. 



1. Scutellum not produced. 



a. Abdomen semi-cylindrical II. Chrysis. 



b. Abdomen subquadrate III. Euchrceus. 



c. Abdomen semi-circular IV. Hedychrum. 



2. Scutellum produced at its apex into a flat mucro . V. Elampus. 



Short generic descriptions will suffice for the ostensible 

 object of this paper, which is merely to facilitate the recog- 

 nition of species, and especially as brief external generic 

 characters will sufficiently mark the discrepancies of the British 



NO. II. VOL. IV. Y 



