THE JUMPING PLANT-LICE OR PSYLLID^ OP THE NEW WORLD. 17 



anatomy, the form of the gonapophyses and many other things 

 indicate a much closer relationship with the higher Homoptera than 

 has been generally supposed. 



COLLECTING AND PKESERVING. 



The Psyllidse, like most Homoptera, are to be found on trees or 

 smaller plants, sucking up the plant juices by means of the long beak. 

 They may be collected with a sweep net, or with tweezers if the insects 

 are not too active — as they often are. The external skeleton is hard 

 enough so that the insect will retain its form after drying. For this 

 reason they may be killed in a cyanide bottle and preserved on paper 

 triangles or minuten nadeln. Or, they may be placed in 70 per cent 

 alcohol and preserved indefinitely in this way. Specimens may be 

 sent by mail, also, in either manner. 



If possible, all stages of the insect, nymphs as well as imagines, 

 should be preserved. The nymphs are best preserved in 70 per cent 

 alcohol. As much data as possible regarding the host-plant, time 

 of year, locaUty, elevation, etc., should be secured and should accom- 

 pany the insect either by means of lot numbers or else on the pin or 

 in the vial of alcohol. 



Specimens for study should be mounted on a paper triangle or 

 minuten nadeln, and not mounted in balsam. The shape and natural 

 form of much of the body surface is not readily visible, because of 

 distortion, in balsam mounts. The finer details of the genitalia, 

 however, are best seen by clearing and mounting the cauda in 

 balsam. 



DETERMINATIONS FROM IMMATURE STAGES. 



Determination of the species when only the nymphal form is 

 available is quite impossible at present. No serious attempt has 

 been made thus far to work out a system of classification based on 

 nymphs only. As soon as sufficient material for this work becomes 

 available, the writer expects to undertake such a task. At present, 

 however, the best that can be done is to determine, sometimes, the 

 subfamily to which the nymphs belong. 



In general, the nymph possesses a flattened oval body, with the 

 long beak on the ventral surface near the center. There are usually 

 three or four instars. After the first molt the wing pads become 

 visible on the anterior half of the dorsal side. The body is often cov- 

 ered or fringed with variously shaped hairs. 



ACKNOWLEDGMENTS. 



I wish to express to Dr. J. C. Bradley and Dr. William A. Riley, my 

 hearty appreciation of assistance and many valuable suggestions 

 during the preparation of this monograph, the former in the taxonomic 

 portion and the latter in the morphology. To Prof. C. F. Baker, 



