THE TRICEOPTERA. 



17 



followed in this course by English writers generally (such as Leach, Westwood, and Stephens) ; 

 and Mr. McLachlan, in his monograph of the European species of the group, also states that his 

 tendency is to separate them from the other Neuroptera. Their relationship to the Saw-flies among 

 the Hymenoptera has been exaggerated ; but, on the other hand, their close affinity to the 

 Lepidoptera, through some of the lower forms of that order, is unmistakable. 



The systematic study of these insects is attended with very considerable difficulties, owing, to a 

 great extent, to the obscurity and minuteness of the distinguishing marks to which it is necessary to 

 have recourse. In general character, in the nature of the metamorphosis, and in the mode of life of 

 the insects thers is such an agreement as would seam to mark them as one family, and by most 

 entomologists they are so treated. To divide them up into subordinate groups (families or sub-families) 

 it is necessary to appeal to very minute distinctive features. Nevertheless, it will be of use to the 

 reader to have a classification of these insects to refer to, and we therefore reproduce here, with 

 some modifications, the table of families given by Mr. McLachlan in his admirable " Monographic 

 Revision and Synopsis of the European Trichoptera," which has already been alluded to : 



DIVISION I. IN^EQUIPALPIA. 



Maxillary palpi, differing in the number of joints in the two sexes- five-jointed in the females: 



A. Form of maxillary palpi similar in both sexes ; those of the male not very pubescent : 



1. Maxillary palpi of the male four-jointed ...... 



2. Maxillary palpi of the mule three-jointed ...... 



B. Maxillary palpi of males two- or three- jointed, very different from those of the females, 



usually very pubescent ......... 



DIVISION II. ^EQUIPALPIA. 



Maxillary palpi, five-jointed, and usually similar in form, in the two sexes : 



A. Maxillary palpi, strongly hairy, usually ascending, the last joint long but simple ; wings 



pubescent ; antenna) long and slender ....... 



B. Pa!pi either rudimentary or long, more or less bent down, with the last joint whip-like, 



composed of numerous minute jointlets ; antennae variable .... 



C. Palpi bent down, rarely hairy, last joint like the others ..... 



D. Palpi simple in structure, very hairy ; antennas short and stout ; insects minute, very 



pubescent and hairy ......... 



The Trichoptera are for the most part moth-like insects, having a smallish head, with the 

 mouth downwards, and usually three ocelli at the vertex ; the antennae are bristle-shaped, generally 

 long, and the first joint is thicker than the rest and more 

 or less elongated ; the eyes are hemispherical ; the wings 

 differ in form, the hinder ones being wider, shorter, and 

 more rounded than the anterior; in repose the wings 

 wrap round the body, and, in consequence, the hind 

 wings are folded. The number of transverse veins in 

 the wings is always very small, and the surface of the wings is, 

 with very few exceptions, clothed with hairs. In the males of 

 a few species the hinder wings are rudimentary, and the females 

 of Enoicyla are almost destitute of wings. The legs have 

 large, conical coxae, meeting in the middle line of the body; 

 and the tibiae are spurred at the apex, and also generally in 

 the middle. 



Species of this group are found in nearly every part of 

 the earth, but they seem to be most abundant in temperate 

 climates. Mr. McLachlan, in the work already cited, enumerates 

 in all 474 species from the European region, which, as limited 

 by him, includes certain parts of Western Asia. If we assume 

 that these constitute about one-half of the known species, 

 we may estimate the total at about 1,000. No doubt this is 

 very far from the whole number of Trichoptera existing on 

 the earth. They are insects which do not greatly attract the 



PHRYGANEID.E. 



LlMNOPHILID^E. 



SERICOSTOMID^E. 



LEPTOCERIDJE. 



HYDROFSYCHIDJE. 

 RHYACOPHILIDJE. 



HYDROPTILID.E. 



LARVA AND NYMPH OF SPECIES OF THE. 

 GENUS LIMNOPHILVS, ENLARGED. 



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