47] LEPIDOPTEROUS LARVAE — FR ACKER 47 



ordinal or biordinal, as described above. In addition, arctians and a 

 few other families show a peculiar specialization. The planta (Fig. 

 100) is longitudinally extended beyond the series of well developed cro- 

 chets, which in these cases are always uniordinal. At each end of this 

 planta is a row of much smaller chitinous processes, usually not hooked. 

 These are often so slightly developed that they are difficult to demon- 

 strate, but the type of arrangement is easily made out by the short row 

 of crochets on the elongated planta. We may apply to this condition 

 the term heteroideous (Fig. 100) now used by botanists for "diversified 

 in form". In distinction from this, crochets of the ordinary mesoseries 

 are called homoideous (Fig. 105). 



Modifications, not well covered by the above terms, are found in 

 Megalopygidae and Lycaenidae. In the former the mesoseries makes a 

 sharp angle cephalad of the middle while the crochets near the angle 

 are as short as those at the ends of the series. The genus Carama has a 

 distinct gap at the angle so that the hooks are in two groups. In some 

 Lycaenidae (Fig. 102) there is a similar gap near the middle of the 

 series and from the planta at this point arises a small fleshy protu- 

 berance. The latter is present in all members of the family altho in 

 many genera the crochets are merely shortened opposite it instead of 

 being wanting. 



Other structures. — Certain genera and families show peculiar spe- 

 cializations which are of value in identification. The most common of 

 these are eversible glands, or osmateria, such as are used in distinguish- 

 ing Papilionidae, Parnassiidae, and Liparidae. The dorsal gland on the 

 seventh abdominal segment of Lycaenidae is also said to occur in all 

 species but is so minute that it is usually overlooked. The ventral pro- 

 thoracic glands of many noctuids, notodontians, and nymphalids are 

 conspicuous enough but their occurrence does not usually depend upon 

 family or generic limits. 



Several kinds of processes of the body wall are less closely associ- 

 ated with setae than are seoli and verrucae. The most common of these 

 are cornicula, or little horns, usually heavily chitinized. They are very 

 often present on the suranal plate. A corniculum is similar to a chalaza 

 in shape but does not bear a seta. 



Certain slender fleshy processes have been given the name, "fleshy 

 filaments", by former authors, and that term describes their structure 

 so well that no further explanation is necessary. They vary from one 

 to many pairs and are found in all Lymnadidae (Fig. 92) and in the 

 papilionid genus Laertias. 



Other projections of the body wall are described in connection with 

 the larvae which bear them. Gibbosities are large round dorsal swellings 



