740 SUMMABY OF CURRENT RESEARCHES RELATING TO 



After lengtliy remarks on the systematic relations of different groups 

 of Diptera, based on the larval characters, he states that the typical, 

 inheiited feature in the entire group of Dipterous larvae appears to be 

 the position of the brain, whether it is contained in a head-capsule, or 

 free, i. e. far behind the mouth or immediately behind the chitinous 

 capsule, supporting some of the mouth-parts, and containing the 

 oesophagus. Less important characteristics are then enumerated. A 

 very unsafe character is the number of visible body-segments. 



The characters of the dipterous larvae in general are laid down and 

 the value of the larval characters in classification discussed. A 

 tabular view of the nervous systems of the larval as compared with 

 the adult Diptera is followed by a section on the character of the 

 sub-orders and families which occupies the greater part of the work. 

 It is succeeded by short descriptions of a few larvae of the families 

 Tabanidae, Leptidae, Dolichopidae, and Empidse. 



Larvae of North American Lepidoptera.* — A. Gruber gives a 

 description of the larvae of some Papilionidae and Nymphalidae ; scanty 

 as his material seems to have been, he thinks that the larvae before 

 him give indications of the possibility of making out the genetic 

 relations of the species. 



The first stage of the larvae of the Papilionidae is distinguished by 

 the constant possession of well-developed warts, on which there are 

 long set« that give a hairy appearance to the caterpillar. They are 

 longest on the most anterior and the most posterior rings of the body 

 and a correlation is apparent between the thoracic and the three last 

 abdominal segments. After each ecdysis the warts decrease in size, 

 and sooner or later disappear altogether ; the smallest, or those on 

 the median segments, are the first to be lost. The function of these 

 warts appears to be that of providing suitable and prominent points of 

 attachment for the setee ; it is to be noted that the warts are rudi- 

 mentary in proportion to the distinctness of the markings on the 

 caterpillar. It is these markings that have been seized upon by 

 natural selection, and the other characters, which have lost their 

 significance, have been gradually suppressed. When the warts do not 

 interfere with the markings, as in the case of larvae with black trans- 

 verse bands, they do not completely disappear until the last ecdysis. 



We may, therefore, suppose that the larvae of the Papilionidae 

 have been derived from forms which were indifferently coloured and 

 not strongly marked, and which possessed strong setigerous warts ; all 

 the larvae in their first and even in their second stage, resemble this 

 hypothetical primitive form. Numerous intermediate conditions are 

 to be observed between it and the conspicuously marked forms found 

 at the present time, and each larva more or less completely repeats, 

 at its ecdyses, the phylogenetic history of its species. 



Further than this, we may suppose that those larvae which retain 

 their warts longest are the oldest forms, or those that stand nearest to 

 the primitive form. 



The Nymphalidae present arrangements which are the opposite 



* JenaisCh. Zeitschr. f. Naturwiss., xvii. (1884) pp. 465-87 (2 pis.). 



