MORPHOLOGY OF THE LEGS OF HYMENOPTEROUS INSECTS. 



445 



&^ 



»."3ss!i^ 



Fig. 6. 



Fig. 9. 



less developec), though still present. 



The cavity is hardly more than an 



inclined plane, the rise at the distal 



end being very slight. The spur ia 



marked by a distinct concavity, and 



the fringe is present in the cavity 



and on the spur, though the brush 



in case is made up of coarser hairs 



than are found in bees or wasps. 



In the species of Chrysidid^e we find this apparatus more perfect than in 



the Ichueumonidse. The cavity is deeper, the spur concave and both show the 



•comb or fringe well marked. The species of this family are unique in that 



the concave spur is fringed to the very point of the blade. 



In the minute Proctotrypidae the antenna cleaner is even less developed 

 than in the Ichneumon flies. The cavity is almost wholly obsolete, the spur 

 is only slightly concave, and the hairs forming the brush are hardly different 

 from the other hairs of the leg. In the Chalcid flies — Chalcididae — the cav- 

 ity is wholly absent, and the only suggestion of this apparatus is in the 

 slightly curved spur. The brush is also obsolete. 

 The same is hardly less true of the gall-flies — 

 Cynipidas. In the saw-flies — Tenth red in id ae — Fig. 

 9, there is no hint of the cavity on the first tarsus; 

 but a slight concavity of the spur, with the mem- 

 brane just visible, still suggests the ''pollen 

 cleaner." In the horn-tails— Uroceridae — the only reminder we have of the 

 antenna cleaner is in the slightly curved spur. The membranous part of the 

 blade is wholly wanting. 



In the study of this apparatus I have been very much interested to note 

 how persistant is its type within each family. I have carefully examined 

 very numerous specimens, and I think we could, from the study of this organ 

 alone, arrange the species of Ilymenoptera, with very few exceptions, in their 

 respective families. The same is also true in many cases of genera. We shall 

 not wonder at this as we come to study the function of the organ and note 

 its great importance. 



No one who has studied bees closely can doubt for a moment the functional 

 importance of the antennae. As touch organs, they are most delicate and 

 wonderful. The work of the hive bee is largely performed in total darkness. 

 Yet very intricate operations are carried on with unerring exactness. This 

 is only possible through the aid of these very sensitive tactile organs — the 

 antennas. There is hardly less doubt that the antennas are the scent organs 

 of insects. And with Hymenopterous insects, especially of the higher fami- 

 lies, the sense of smell is of exceeding importance. It has been thought 

 also that the antennae serve as organs of hearing. We see then that it is of 

 the highest importance that these organs be kept free from all dust. Bat 

 the very habits of most Hymenopterous insects, visiting, as they do, flowers 

 laden with pollen, as do all except the lowest families, or digging in the mud 

 and dust, as do many bees and wasps, tend to soil the antennae. And it is no 

 more necessary for the microscopist to brash the lenses of his objectives than 

 for the bee or wasp to dust its antennse. 



