92 W. WESCHE ON SOME NEW SENSE-ORGANS IN DIPTERA. 



of touch, or feeling, and vision with exactness, as all imaginal 

 insects can feel through the hairs and bristles embedded in their 

 chftinous coverings, and nearly all can see by means of their eyes, 

 simple or compound ; while there is little doubt but that most, 

 if not all, can smell. What is the exact seat of the organ of 

 scent, however, is not determined, as while the antennae have 

 been proved in some species to be the chief centre of excitation 

 of the olfactory nerves, the palpi, and even parts of the body, 

 may support organs sensitive to smell. 



Professor Packard has found sense-pits on the palpi of Perla * 

 which he thinks may be organs of taste, though he quotes Platen, 

 Will, and Forel as having proved that in the Wasps and Ants the 

 palpi have no gustatory function. Little is known as to these 

 organs of taste, but it is evident that they exist in those insects 

 which feed in the imaginal state, and must be situated in the 

 mouth, or in its immediate neighbourhood. In Diptera they are 

 said to be seated in the labella (paraglossae), and as far as my 

 observations go this seems probable, except in those genera such 

 as Chironomus, Psychoda, and Oestrus, in which many species do 

 not feed in the imaginal state, but whose mouth-parts, except 

 in the Oestridae, seem quite adapted for use. 



Lord Avebury t quotes Kraepelin as finding certain peculiar 

 club-shaped hairs at the end of the proboscis of the humble-bee 

 (Bombns), which he considers to be taste hairs ; F. Will as 

 thinking certain pits on the maxillae of a wasp {Vespa vulgaris) 

 to have the same use — these he calls taste cups ; and Leydig, 

 Meinert, Lowne, Kraepelin and others as considering as taste 

 hairs two rows of minute pits, with a central papilla, situated on 

 the proboscis of the hive bee (Apis melifica). 



I have examined these structures with modern objectives, and 

 I remain very sceptical as to the uses of one of the parts. The 

 humble-bees of which I have preparations in my cabinet only 

 show Kraepelin's club-shaped hairs in one species ; but the mere 

 fact that they are not present in all the species of a genus 

 militates against regarding them as characteristic sense-organs. 

 Further, all these insects, including the possessor of Kraepelin's 

 " club-shaped hairs," have the taste hairs on the labium exactly 

 similar to, and obviously homologous with, those of the hive bee, 



* Textbook of Entomology, 1898, p. 272. 

 f Senses of A id in als, p. 28, 29. 



