6 NATURAL HISTORY. 



branches of the rose-bush, The well-known oak-apples, which many people still wear on King 

 Charles's Day, are another form of galls. They are produced on the twigs of oaks by the puncture 

 of Teras terinincdis. A very curious form of gall, which would generally be taken rather for a 

 parasitic fungus than a gall, is to be found upon oak leaves in every wood. This is a little flat round 

 disc attached to the surface of the leaf by a very small portion of its lower suiiace. Such galls are 

 produced by two or three species of Neuroterus, which may be easily bred from them, if the leaves are 

 collected in the autumn. JBiorhiza aptera, a wingless species, lives on the roots of the oak. 



Singularly enough, we have in this family once more to record cuckoo-like habits, many species 

 of Gall Flies depositing their eggs in the galls produced by other species. The larvae hatched from 

 these eggs feed upon the substance of the gall, and in the end devour the rightful possessor. 

 These parasites belong to the genus Synergus, a common species of which (S. vulyaris), black, with 

 the mouth, antennae, and legs red, breeds in the galls of Cynips quercus-folii. 



The truly parasitic species form several distinct genera. Ibalia cultellata, a large species, 

 measuring half an inch long, black, with a red, knife-shaped abdomen, is parasitic upon the larva? 

 of wood-boring Beetles, or, according to some writers, upon that of the Tailed Wasp (Sirex). 

 The species of Figites live upon the larvae of Flies, and those of Allotria upon Aphides. None 

 of them appear to attack insects belonging to their own family, but the true Gall Flies by no 

 means have an immunity from parasites. Many Ichneumonidae, and especially Chalcididae, pierce 

 the substance of the galls with their long ovipositors, and place their eggs in the contained larva. 

 Thus Callimome bedeguaris (p. 4) haunts the Bedeguar galls, and another species of the same 

 genus even makes its way underground to place its progeny in the root-galls of Biorhiza. 



A remarkable circumstance connected with the insects of this family is that of a great number 

 of the supposed species, especially those of the genus Cynips, only the females are known, the most 

 pertinacious investigation having failed to reveal any males. Hence entomologists, headed by 

 Mr. Siebold, long since came to the conclusion that as the unimpregnated females undoubtedly 

 produce galls, we have here to do with a case of parthenogenesis. Recent researches have shown 

 that in some cases, at any rate, what has been called an "alternation of generations" takes place; 

 that is to say, that the parthenogenetic females are the offspring of male and female insects, 

 so different from them in character as to be placed in different genera. 



TRIBE III PHYTOPHAGA. 

 FAMILY UROCERID^E, OR TAILED WASPS. 



The remainder of the Hymenoptera, forming two families, are, as already stated, confined 

 to a vegetable diet in all stages of their existence. The perfect insects are recognisable at once 

 by their sessile abdomen, and the larvae are more or less caterpillar-like, possessing six legs, and 

 generally a number of pro-legs,' and having a hinder opening to the intestinal canal. 



The two families may be distinguished by various characters, but especially by the structure 

 of the ovipositor. In the present family this organ generally projects considerably from the apex 

 of the abdomen, and consists of essentially the same parts as in the preceding families, that is 

 to say, two lateral plates, and a central, more or less serrated style, grooved along its lower surface. 

 The antennae are filiform, and consist of from eleven to twenty-four joints the eyes and ocelli 

 are well developed ; the abdomen is elongated, usually nearly cylindrical, and composed of nine 

 segments, with the dorsal plate of the first segment divided ; and the anterior tibiae have only 

 a single spine at the apex. The larvae resemble the grubs of Beetles rather than Caterpillars ; 

 they have six thoracic legs, which are often rudimentary, and generally no trace of pro-legs. 



These insects present certain rather remarkable peculiarities of structure, such as the division. 

 of the dorsal plate of the first segment of the abdomen already alluded to, the purpose of which 

 is at present unknown ; the exceedingly fi'ee articulation of the neck-like prosternum with the 

 pronotum, which gives the head great freedom of motion ; the movable junction of the meso- 

 and metathorax, which exists in this and the next family, and is a very exceptional chai'acter 

 in the class of insects ; and the presence of two transverse openings on the metaiiotum, the so-called 

 " false stigmata." the function of which is unknown. 



The family is not an extensive one, and its species occur chiefly in Europe and North America, 



