Coleoptera 



225 



this position they are fertilised by the free-flying male. The tiny 

 campodeiform larva; are hatched within the mother's body. Escap- 

 ing to the outer surface of the bee-host they are carried to her 

 nest, where they bore into a bee-grub and become changed into 

 legless maggots. The presence of the parasite does not hinder the 

 development of the bee-larva, but when the latter has undergone 

 the final change it flies carrying the Stylopid — if a female — within 

 its abdomen. The Stylopidz are probably widely distributed, but 

 little is known of them outside Europe and North America 



Fig. 124. — Bark-Beetle {Scolytus rugtdosus, Ratz.), Europe, a. Beetle from 

 above ; b. side view ; c. pupa ; d. larva. Magnified 10 times. From 

 Chittenden, Circular 29 (2nd ser.), Div. Ent. U.S. Dept. Agr. 



ORDER 12.— TRICHOPTERA. 



Structure. — This order comprises the Caddis- 

 flies, which were formerly united with the Neurop- 

 tera. Their structure is, however, very distinct. 

 The wing-surface, as well as the insect's body, is 

 covered with hairs. The fore-wings are long and 

 narrow, the hind-wings usually broad and somewhat 

 shorter, with folding anal area ; the neuration is pre- 

 dominantly longitudinal, the principal nervures forking 

 repeatedly and being connected by few cross nervules. 

 A fold of membrane (jugum) at the base of each wing 

 is a characteristic feature. Mandibles are absent, and 

 the two pairs of maxilla are united to form, with the 

 upper lip, an imperfect sucking apparatus (139) ; the 

 feelers are long, slender, and many-jointed. The palps 

 of the first maxillae have five segments in the females, 



