442 



MISS A. M. EVANS ON THE STRUCTURE AND OCCURRENCE 



close correspondence between the construction and arrangement of the hypo- 

 pharynx and labium in a Tenthredian larva and that of Sialis. I have 

 further suggested a possible mode of derivation of the condition in larval 

 Lepidoptera and Trichoptera from one less specialised such as we found in 

 larval TenthredinePG. If there is any foundation for these suggestions then 

 the Neuropterons types studied have afforded some clue to the mode of 

 development of the highly specialised labio-hypopharyngeal structure of 

 Lepidoptera from the free tongue and generalised labium of Forficula. They 

 have, further, made it apparent that the possession of a pair of lobe-like 

 projections is. a feature of the hypopharynx in the Neuropterons forms 

 studied-. In dealing with the Tenth'redinese, reasons are given for assuming 



Text-fig. 9. 



Ilemerohius sp. Labium and hypopharynx, dorsiil aspect, h. Hypopharynx. 

 I. Dorsally flexed ligula. 1. p. Labial palp. m. Maxillula. s. Sclerite 

 supporting hypopharynx. 



that the corresponding structures (m.) in that family are homologous with the 

 maxillce of Lepidopterous larva? I suggest, therefore, that in Neuroptera 

 we find a condition of hypopharynx and maxillulse intermediate between 

 that of Forficula and larval Lepidoptera. 



COLEOPTERA. 



In the larva of Helodes Carpenter and McDowell (9. pp. 373-96) have 

 described and figured a pair of articulated appendages, one at each side of 

 the hypopharynx. 



