1 2 Mr. T. Desvignes' Observations on 



III. Observations on Two of Gravenhorst's Subgenera of 

 Ichneumons, namely, Macrus, forming the Fifth Family 

 of Ophiorij and Coleocentrus, the Fourth Family of 

 Banchus. By Thomas Desvignes, Esq. 



[Read 4th June, 1849.] 



I have brought with me two insects for exhibition, which I 

 captured in an unfinished building in Vienna; and at the time I 

 considered to be the sexes of one species ; since then closer in- 

 vestigation has convinced me in this particular. Their palpi and 

 neuration of the wings perfectly correspond, independent of other 

 minor points. Gravenhorst makes no mention of the construction 

 of the former. The maxillary palpi consist of five articulations: 

 the basal short; 2nd, stout, reniform ; 3rd and 4th, slightly sub- 

 clavate; the 5th filiform, the apex somewhat mucronate, their 

 comparative lengths 5, 3, ■§, 1. The second articulation of the 

 labial palpi cylindrical, and a little longer than broad, incurved, 

 and stouter than the rest ; all are setose. The antennae of the 

 male are setaceous, those of the female filiform; the joints of the 

 latter lay parallel, but obliquely one to the other, and are longer 

 than in the $ , of which the specimen here exhibited agrees per- 

 fectly with Gravenhorst's Macrus longiventris, and the female 

 with his Coleocentrus excttator. 



The specific characters in these two subgenera are scarcely 

 distinct, with the exception in the form of the abdomen. In re- 

 ferring to the generic descriptions as given by Gravenhorst, their 

 difference consists in the form of the scutellum, which in Coleo- 

 centrus is triangular, and in Macrus subquadrangular; the basal 

 abdominal segments, and the eighth or apical ones in both, agree 

 in form, the latter in the 2 is more reflexed than in the $ . 



The vomeriform appendage in the ? is stated hy Gravenhorst 

 to have its origin from the sixth ventral segment ; but upon 

 closer examination it appears to me to consist of three counter 

 segments, the first arising from the apex of the third ventral seg- 

 ment. This may be erroneous, and arising only from the greater 

 production of the ordinary segments. In Arotes and Acoenites, the 

 $ of which are similarly constructed, this appears to be the case, 

 and forms a continuation of the ventral carina, but the upper and 



lower margins of the segments of 1 excttator do not coincide 



as in the two last genera ; this has led me to come to the former 

 conclusion as regards that insect. 



