162 ENTOMOLOGY 
Thysanuriform Larvee.—Two types of larve are recog- 
nized by Brauer, Packard and other authorities: thysanuri- 
form and eruciform,; respectively generalized and specialized 
in their organization. The former term is applied to many 
larve and nymphs (Fig. 210, C, D) on account of their resem- 
blance to Thysanura, of which Campodea and Lepisma are 
FIG. 210: 
Types of larve. A, B, Thysanura; C, D, thysanuriform nymphs; E-J, eruciform 
larve. A, Campodea; B, Lepisma; C, perlid nymph (Plecoptera); D, Libellula 
(Odonata); E, Tenthredopsis (Hymenoptera): F, Lachnosterna (Coleoptera); G, 
Melanotus (Coleoptera); H, Bombus (Hymenoptera); J, Hypoderma (Diptera). 
types. The resemblance lies chiefly in the flattened form, hard 
plates, long legs and antennz, caudal cerci, well-developed man- 
dibulate mouth parts, and active habits, with the accompanying 
sensory specializations. These characteristics are permanent 
in Thysanura, but only temporary in metamorphic insects, and 
their occurrence in the latter forms may properly be taken to 
indicate that these insects have been derived from ancestors 
which were much like Thysanura. 
Thysanuriform characters are most pronounced 1n nymphs 
of Blattidee, Forficulidze, Perlidee, Ephemeridze and Odonata, 
but occur also in the larvee of some Neuroptera (Mantispa) 
and Coleoptera (Carabidze and Meloide). These primitive 
characters are gradually overpowered, in the course of larval 
evolution, by secondary, or adaptive, features. 
