INSECTA. 575 



hooks or scales. In the Ephemeradae, the mandibles are 

 obscure, the tarsal joints four in number, and the terminal 

 ring of the abdomen furnished with setae, as in Ephemera, 

 Baetis, and Cloeon. 



In other families, the antennae are much longer than the 

 head, and consist of sixteen joints and upwards. Among 

 these the Panorpadae, including Panorpa, Nemoptera, Bit- 

 taces, and Boreus, have the front produced into a snout. 

 The remaining families have the front short. In the Myr- 

 melionedae the antennae are clavate, and the palpi six in 

 number, as Myrmelion and Ascalapus. The two remain- 

 ing families have filiform antennae. The Termesidae have 

 from two to three tarsal joints, as Termes and Psocus. 

 The Hemerobiadae have four or five tarsal joints, as He- 

 merobius, Raphidia, Mantispa, Scalis, Corydalis, Chaulio- 

 des, and Osmylus. The Perladae, including Perla and 

 Nemoura, have the inferior wings folded longitudinally. 



Order V. TRICHOPTERA. 



The wings of the trichopterous insects are four in num- 

 ber, and membranaceous. The upper ones are usually of 

 a darker colour and firmer consistence than the lower ones. 

 The ribs, which are usually hairy, are disposed longitudi- 

 nally, and when they do anastomose, the intervening spa- 

 ces are lengthened. The lower wings fold longitudinal, 

 ly. The mouth has a distinct labrum ; the maxillary 

 palpi have five joints. The labial palpi have only three 

 joints, the last of which is a little enlarged. The maxillae 

 and labium are united, but do not form a sucker. There 

 are two large compound eyes, and two ocelli. The legs 

 are spinous, and the tarsal joints five in number. The 

 larvae live in the water in tubular dwellings, which they 

 construct, and move about with, open at both ends, and 

 consisting of bits of stick, sand, or shells. Hence they are 



