ORDER HYMENOPTERA 



THIS great order of insects, which contains the bees, wasps, 

 ants, gall-flies, saw-flies, ichneumon-flies and related forms is 

 unsurpassed in interest by any other group of animals. It is a 

 very large order, and comprises nearly 30,000 described species; 

 but the enormous number of undescribed species, particularly of 

 the smaller parasitic forms inhabiting tropical regions and other 

 out-of-the-way localities would probably swell this number to 

 more than 300,000. To indicate the work still to be done in this 

 order it is safe to say that a day's collecting in Central Park, New 

 York, almost under the windows of the great American Museum 

 of Natural History, or in Logan Square, Philadelphia, within 200 

 yards of the Academy of Natural Sciences, would result in the 

 capture of a number of species new to science. But the size of 

 the order is its least important and interesting feature. The very 

 great variation in habits and life history, the wonderful social 

 organization of the bees, ants and some wasps, the seeming mar- 

 vellous intelligence of these creatures, the remarkable adaptations 

 of structure to environment, the extraordinary interrelations and 

 interdependencies of species seen with the members of the 

 parasitic families, the strange vital phenomena of sex-abortion, 

 of virgin birth or parthenogenesis, and the wonderful plant de- 

 formations brought about by the gall-makers, unite to render the 

 Hymenoptera a field of study of never-ending interest. 



As a group the Hymenoptera are distinguished from other 

 insects by the following points: Their metamorphoses are com- 

 plete, their mouth parts are mandibulate, and in most families 

 formed for biting, although in the bees they are so modified as 

 to form a sort or proboscis, and the females are furnished with 

 an extensile sting or ovipositor. All have four wings, of which 

 the hind pair is smaller. The wings are membranous, usually 

 transparent, bear no scales, and are divided by veins or nervures, 

 as they are inappropriately and misleadingly called, into a com- 

 paratively small number of cells. 



On account of the great diversity of form and structure 

 which exists within these limits, the Hymenoptera have long 



