146 ARTHROPOD A. 



Order IX. HYMENOPTEEA. 

 PIEZATA. PHLEBOPTERA. 



Four naked, membranous, unequal few-veined wings. Mandi- 

 bulate ; labium and maxillae more or less elongate. Larvae apodal 

 [excl. Terebrantia]. Pupa incomplete, inactive. 



The mouth has two robust mandibles, protected by a labrum 

 above, and two united maxillae forming a sheath for the labium, 

 when developed into a suctorial proboscis, below, and two pairs 

 of palr,i. The mandibles, however, are chiefly employed in the 

 construction of the nest ; the labium, when used as a sucking-organ, 

 is retractile. 



The abdomen, mostly attached by a pedicel to the thorax, is in 

 the female furnished with an ovipositor, which is frequently 

 modified into a sting [aculeus], or in one group into saws [serrae], 

 and in another into a borer [terebra]. It consists normally of 

 six pieces, the two outer forming a sheath. The mesothorax forms 

 the bulk of the thorax, the other two parts being but moderately 

 developed. The wings are always horizontal, the upper pair fre- 

 quently with a chitinous nodule (tegulum) at the base ; the lower 

 pair along its anterior margin is provided with a series of minute 

 hooks, which catch into the reflected posterior margins of the 

 upper wings, for the purpose of keeping them together during 

 flight. On the upper wings is an opaque spot, as in the Neuro- 

 ptera, named the " stigma." 



Wingless species (but the absence of wings frequently depending 

 on sex) are frequent. Female ants, after pairing or when pre- 

 paring to lay their eggs, shake off their wings, a small portion, 

 however, generally remaining. The wings, as in Chalcididae, 

 are sometimes almost destitute of venation. Some species are 

 eyeless, or are without mandibles, or without a sting. Never- 

 theless the order cannot be said to contain any aberrant or 

 abnormal forms, except among the neuters ; these are undeveloped 

 females peculiar to the Hymenoptera, with the sole exception of 

 white ants among the Neuroptera. 



In the aculeate Hymenoptera a poison, strongly impregnated 

 with formic acid, is secreted by a special gland. 



Galls, although produced by other insects, and even by worms, 

 are in this order almost exclusively caused by Cynipidae. These 

 insects deposit their eggs in the leaves, stems, and roots of plants. 

 Different kinds of galls are seen on the same plant, produced by 

 different species of gall-flies. Some galls contain but a single 

 egg, as those of Cynips gallcB-tinctorice ; in other galls more than 



