210 ENTOMOLOGICAL SOCIETY 



being nearly equal; in fig. 17 the outer and the inner are equal, 

 or nearly so, arid larger thanUhe two middle teeth; in fig. 18 the 

 teeth are much smaller and all about equal ; in figs. 19 and 20, 

 the one with four, the other with three, the inner tooth is blunt 

 or truncate; while in figs. 21 and 22 both are bidentate, but 

 the outer tooth in one is much longer than in the other. 



In some genera both mandibles may be 4-dentate or 3-dentate ; 

 in others they are 3-dentate in one mandible and 4 in the other. 

 All these characters are important in descriptive work. 



Our systematic workers have not given enough attention to the 

 structure of the mouth-parts of our parasites, although they 

 undoubtedly afford excellent characters for generic diagnoses. 



To show how variable and valuable they are in systematic 

 work, I have given some rough drawings, Plate IV, representing 

 types found in three different families the Ichneumonidae, 

 Braconidas, and Chalcididag. 



Fig. i represents the mouth-parts of Ichneumon (after Ratze- 

 burg). Here the labial palpi are 4-jointed, the maxillary palpi 

 5-jointed, the galea being developed into strong, broadly rounded 

 lobes, while the mentum, maxilla, and other parts have shapes 

 peculiarly their own. 



Fig. 2 represents the same parts of a Braconid belonging to 

 the genus Microgaster. The labial palpi are only 3-jointed, the 

 galea less strongly developed, while the other parts are quite dif 

 ferently shaped from those in Ichneumon. 



Figs. 3 and 4 represent the mouth-parts of two Chalcids one 

 a Pteromalus, the other a Eurytoma. Here the maxillary palpi 

 are only 4-jointed; the labial palpi, although 3-jointed, have the 

 second joint very small ; while the mentum and galea are quite 

 distinct from both Bracon and Ichneumon. 



Fig. 4 represents Eurytoma. You will notice a marked dif 

 ference in the shape of the galese between it and Pteromalus. 

 These are long and acuminate or lanceolate, while the other parts 

 are correspondingly different. 



All through this immense family, comprising thousands of 

 species, many different types of mouth-parts occur, w r hich I be 

 lieve, in connection with other characters, justify us in dividing it 

 into several distinct and well-marked families, The labial palpi 



