MORPHOLOGY OF THE ALEYRODIDyE. 13 



tance cephalad from the tip of the ovipositor. In Dialeurodicus it ap- 

 pears to be very similar in shape, but in Aleurodicus it is narrower 

 and more elongate, while in Paraleyrodes it is rounded. What ap- 

 parently corresponds to the subgenital plate liere is a large structure 

 covering the caudal ventral portion and extending some distance 

 dorsad on each side. The structure of the ovipositor is considerably 

 like that found in the Psyllida?, while it differs quite markedly from 

 the structure present in the Aphiclidse. It is composed of six parts, 

 the outer covering of which usually bears a definite number of hairs. 

 These parts are grouped into pairs. The inner and upper pair of 

 these is usually distinct for some distance, at least, and the parts are 

 easily separable. The outer pairs, however, have grown together 

 almost entirely and appear as one pair. Occasionally, though, they 

 can be seen split at their tips, as is the middle pair, and they arc 

 sometimes sculptured or serrate. Extending throughout the ovi- 

 positor there are a number of chitinized rods. These appear to be 

 composed of parts jointed together and working one against another. 

 There are present toward the tip flattened structures which appar- 

 ently correspond to the " sting palpi " of the PsyllidcC. The ovaries 

 are two in number and very large. They are composed of five-cham- 

 bered ovarian tubes and in some cases almost entirely fill the abdo- 

 men. The receptaculum seminalis is ventral and the oviduct, coiling 

 upon itself considerably, opens between the valves of the ovipositor. 



LEGS OF THE ADULT. 



The rudiments of the legs appear very early in the embryonic state, 

 at about the same time as those of the m6uthparts. A study of the 

 legs of the adults is interesting, as it tends to throw some light on 

 l!ie position of the family. The three pairs are considerably alike, 

 varying only in the relative lengths of the different segments. The 

 femora and tibijc are elongate and armed with spines and hajrs. The 

 tibiae especially possess several longitudinal rows composed of 

 prominent spines placed close together. On the distal third these 

 become fewer in number, excepting for a comblike structure, which is 

 found in at least several species. The distal end of the tibifc is sur- 

 rounded by a number of short spines which, though much weaker, 

 suggest the jumping spines of the Psyllida'. The tarsus is composed 

 of two segments almost equal in length, and in this regard it is nuich 

 closer to the Psyllidai than to the Aphididse, in which one segment is 

 very much reduced, or to the Coccidac and some Aphidida?, in which 

 it is altogether lost. Attaching the claws and paronychium to the 

 tarsus proper are a number of irregular pieces difficult to make out 

 and which may be part of the tarsus. The foot itself seems much 

 nearer to that of the Psyllida; than to that of the Aphidida^, for the 



