LARVAL HEAD OF SOME CHIRONOMIDAE — GOUIN 187 



and the assemblage of the labral elements, the absence of premandibles, the 

 multiplication of the mandibular teeth and correlatively the hypochilan teeth. 



c. The chironomian structure adds a few individual characteristics to the 

 fundamental traits: (i) the labral and epipharyngeal elements are pectinate, 

 particularly the very distinct individualized median chaeta and the centro- 

 epipharyngeal chaetae; (2) correlatively the dorsal brush; (3) the presence of a 

 brush close to the messorial tip; (4) the anterior part of the ventral wall is 

 double, the internal wall (which is the "striated plate") is soldered to the 

 hypochilan "rabat," correlatively with a different insertion of the maxillary 

 base. 



The general structure of the family is thus specified by these three 

 modifications, typical for the subfamilies Orthocladiinae, Podonomi- 

 nae, and Chironominae. However, the great resemblance in the dis- 

 position, the connections, and the conformation of the constituent 

 elements authorized the joining of these three types under the com- 

 mon term of "generalized orthocladian structure," for the ortho- 

 cladian type is truly the structure which is nearest to the generalized 

 type. To this structure is opposed the "tanypin" structure, very 

 distinctly correlated with the strictly carnivorous regimen, the study 

 of which forms the subject of the following section. 



THE STRUCTURE OF TANYPINAE : THE LARVAL HEAD 

 OF MACROPELOPIA CF. NEBULOSA MG. 



The anatomy of the larval head of Chironomidae in the predaceous 

 larvae of the species grouped in the subfamily Tanypinae presents 

 remarkable structural details. They have been the subject of a paper 

 by Zavfel {in Thienemann and Zavfel, 1916-1917, p. 575 sq.), the 

 data of which are reviewed and completed in the following study. 



The whole behavior of these predaceous larvae, the length of the 

 pseudopoda, the flexibility of the abdomen, the retractibility of the 

 antennae, the falciform mandibles moving in frontal planes, the 

 powerful cephalic cibarial and pharyngeal musculature, the extensi- 

 bility of the oesophagus — all these characters and many others are 

 strictly correlated with the mode of life. The animal, looking for 

 its prey, advances in slow and rather extensive movements, often 

 stops to explore the area by shaking its antennae, places its head and 

 its thorax as if to proceed in a swift current, its abdomen, stretched 

 like a spring, always highly buttressed above the posterior pseudopoda. 

 Then, when it has thus been drawn by stages to within reach of its 

 pseudopoda, with a sudden movement of relaxation it projects its 

 body forward and implants its hooks into the soft body of its victim. 

 It will ingest the prey completely, thanks to its maxillae being abun- 



