132 MANDIBULAXA. IS'liUKOl TEKA. 



of the segments faintly yellowish ; wings hyaline, stigma the same and 

 colourless ; nervures fuscous. 



Found in June, near London. 



Section V.— MEGALOPTERINA, Mac Leay. 



Antennas moderately long, setaceous, articulations numerous, rarely very 

 distinct : palpi filiform or setaceous : labrum existed, transverse, entire 

 mandibles small : head rather large, sometimes depressed : eyes moderate : 

 ocelli three, or wanting : thorax with its anterior segment, or collar, large, 

 more or less quadrate : ivings ample, deflexed or incumbent, posterior 

 sometimes largest ; nervures distinct, frequently variable on the two sides 

 of the same individual : abdomen somewhat curved or elongate, occasionally 

 furnished with two setae at its apex : legs longish and simple, sometimes 

 compressed : tarsi with five joints, and the last but one bifid, or with three 

 joints and nearly simple. 



The insects included in this section of the order differ considerably 

 in habit from the remainder : they have in general longish setaceous 

 antennae; the head broad, mostly depressed, and more or less 

 inflexed ; are either destitute of ocelli, or have three placed in a 

 triangle ; their wings are ample, resemble .each other, are rather 

 coarsely veined, the nervures occasionally diff'ering in the same 

 example : the anterior pair are sometimes largest ; at others the 

 posterior are most ample, and, although not longer, their surface is 

 larger from their superior width : they are either deflexed or hori- 

 zontally incumbent. The following families are found in Britain : — 



Ocellis nullis : alis deflexis : . . . . . .1. SialidjE. 



3-bus, in triangulum dispositis : alis incunibentibus : . .2. PEHLiDiE. 



Family I.— SIALID^E, Leach. 



AntenncE inserted on the front of the head between the eyes, rather longer than 

 the thorax, and composed of numerous simple articulations: mandibles 

 small, horny, abruptly hooked at the tip, acute, toothless : palpi filiform ; 

 maxillary long, four-jointed, labial 3-articulate, all with the terminal joint 

 rather attenuated at the base and obtuse at the tip : head transverse, de- 

 pressed, nutant, as broad as the thorax : ocelli wanting : ivings of nearly 

 equal size, posterior smallest, deflexed, coarsely but somewhat remotely 

 reticulated, the anterior pair dilated at the base of the costa, and all 

 destitute of a stigma : legs aimple: iJam five-jointed, with the penultimate 

 joint bifid, heart-s^haped. Larva elongate-conic, depressed, with -six lees-i 



