HYMENOPTERA 175 



flies) . The stinging Hymcnoptcra, on account of their efficient 

 means of defense, are often mimicked (Fig. 132, p. 160) the 

 bumble-bees by the hawk-moths, the hornets by two clear- 

 winged moths of the genus Sesia, the bee by the drone-fly 

 (Eristalis), the wasp by a common English beetle (Clytus 

 erictus), and the hornet by a Nicaraguan Hemiptera. 



Saw-flies and "Horntails." Among the boring Hymenoptera are the 

 saw-flies, horntails, and gall-flies. 



The saw-flies have a wide head and thorax, with a broad joining of the 

 base of the abdomen and thorax. The ovipositor consists of a pair of saws 

 with which slits are made in leaves or stems where the eggs are laid. The 

 larvse look much like caterpillars, but may be distinguished by having from 

 twelve to sixteen pro-legs instead of ten. Most of these larvae have " a 

 curious habit of curling the hind end of the body sidewise " about a branch. 

 The rose-slug and currant-worm are familiar examples. 



The currant-worm is the larva of 

 the saw-fly (Nem'atus ribe'sii). It is 

 a " criminal emigrant " and has left 

 a large army of descendants. The 

 female deposits her glossy white eggs 

 along the ribs of the first leaves of 

 currant and gooseberry bushes. In 

 ten days the little whitish Iarva3 

 hatch. They are voracious feeders 

 and will strip a bush of every leaf if 

 allowed to mature. When mature 

 they are green with a black head and 

 black spots and resemble caterpillars. 

 They pupate in brownish paper-like 

 cocoons, either attached to the bush 

 or hidden in the ground. There are 

 two broods in a season, provided the 

 first is not exterminated by a liberal Fig. 145. Boring saw-fly or horn- 

 spraying with Paris green or hellebore. tail (TrZ'mex col&m'ba). 

 If the spraying is thoroughly done 



when the worms are quite small, they are easily poisoned, since, like all 

 insects with biting mouth parts, they swallow the poison with their food. 

 If any of the larvse escape, the spraying must be repeated for the second 

 brood, or the bushes may be killed outright in one season. If the spraying 

 is done soon after the first brood hatches there is no danger of poisoning the 

 fruit. 



The horntails (Siric'idce) are so named because the posterior end of the 

 abdomen bears a spine or " horn." They differ from the saw-flies in hav- 

 ing an ovipositor " which is composed of five long, slender pieces," adapted 

 for boring instead of for sawing. There are several species in America. 



The pigeon horntail (TrZ'mex col&m'ba) (Fig. 145) has a cylindric body 

 about \ inch in diameter. It is 1J inches long, with rusty red thorax and 

 black abdomen, with yellow bands and spots on the sides, a yellow " horn- 

 tail," and smoky transparent wings. The female pierces holes about \ inch 

 deep in elm, oak, sycamore, or maple trees, bending the ovipositor at right 



