FIELD BOOK OF INSECTS, 



scale or knot, strongly differentiated from the rest of the 

 abdomen. (In what follows I will leave off the word 

 "apparent"; really the first abdominal segment of all 

 but the Tenthredinoidea is so closely fused to the thorax 

 that it does not appear as part of the abdomen and may, 

 for practical purposes, be forgotten.) The Formicoidea 

 are the True Ants and the workers are always wingless. 

 Seep. 415. 



In groups h toj the petiole is not scale-like or nodiform; 

 body often hairy. 



(h) APOIDEA. First segment of hind tarsus (basi- 

 or metatarsus) expanded, flattened, and usually very 

 hairy; trochanters one- jointed; many of the hairs branched; 

 adults always winged. Bees; see p. 439. 



In groups i and j (as well as in other Hymenoptera 

 which are not bees), the basitarsus is not as described for 

 bees and the body-hairs are not branched. 



(i) VESPOIDEA. Pronotum extending back so that 

 its hind angles or tubercles touch or reach above the 

 tegulae (scale-like bodies, one in front of the base of each 

 wing) ; wingless forms are densely hairy; some of the winged 

 forms fold the front wings longitudinally when at rest. 

 Seep. 425. 



(j) SPHECOIDEA. Hind angles of pronotum remote 

 from tegulas and on a lower level (this is true also of the 

 bees); never wingless; front wings never folded. See 



P- 431. 



TENTHREDINOIDEA 



The ovipositor of the female Saw-fly consists of an 

 external, flattened plate on each side ("saw-guides") 

 and two flattened, pointed, yellowish plates ("saws") 

 between them. The larvae either feed on the leaves of 

 plants or within their stems, including tree-trunks; some 

 of them make galls. Saw-fly larvae have only one ocellus 

 on each side of the head, w r hereas caterpillars have several; 

 also their abdominal legs, if present, do not have the circles 

 of hooklets possessed by Lepidoptera. The larvae of 

 Siricidae and Cephidas are practically legless; when saw- 

 fly larvae have abdominal legs, there is always a pair on 



408 



