358 HALF HOUKS WITH INSECTS. [Packard. 



found in the antennae. Similar organs also occur at the end 

 of the palpi. I have found a similar isolated sac on the 

 under side of both the labial and maxillary palpi of a Perla 

 (Fig. 99). It is probable that this is an olfactor}^ organ, and 

 placed on the under side of the feeler, next to the mouth, 

 so as to enable the insect to select its proper food by its 

 odor, giving an additional sensory function to the palpi of 

 insects, which are supposed to be organs of touch. 



In the blow fly there are a number of these organs situ- 

 ated at the base of the wings and near tiie spiracles or 

 breathing holes. Similar organs are found in the wings of 

 the carrion beetles and are supposed to be olfactory in their 

 function. 



There are also sense organs, probably ears, on the fore 

 legs of certain species of grasshoppers. Sense organs even 

 occur in tiie jointed appendages of the hind body or abdomen. 

 Our attention was first called to this fact by the discoverj^ 

 by Dr. Dohrn of sense organs in the jointed appendages of 

 the mole cricket. Stimulated by this I examined the long, 

 slender, jointed feelers of the cockroach, and to my great 

 joy found ninety-five of these little pits on one, and one 

 hundred and two on the other. It is evident that the crea- 

 ture is provided with a double set of antennae, one on the 

 head and another on the tail. True abdominal antennae 

 seem also to occur on the abdomen of the Mantis. 



I have also found sense organs similar in appearance on 

 the abdominal appendages of a fly (Chrysopila), and it is 

 not improbable that these organs will be found in similar 

 situations in other insects. They are thus scattered at ran- 

 dom, as it were, over the surface of the body. No wonder 

 that insects are so alive to impressions from without ! 



Without much doubt the nerves distributed to tliese or- 

 gans are nerves of special sense, and as the ganglia from 

 which they arise may be situated near the end of the abdo- 

 men or in the thorax as well as in the head, it appears that 



6 



