A HISTORY OF NOTTINGHAMSHIRE 



differences in the mode of life of the insects in the two groups. The Sessiliventres or Sawflies are 

 vegetable feeders ; the larvae mostly resemble the caterpillars of Lepidoptera, and usually feed 

 exposed on the foliage of plants, while those of the Petiolata are maggot-like and incapable of 

 obtaining food by their own exertions : a large proportion of them are carnivorous, living as 

 parasites in the bodies of other insects. A remarkable feature in the economy of the Hymenoptera 

 is the frequent occurrence of parthenogenesis, i.e. the production of young by the female insect 

 without the co-operation of a male. While in some cases it may be of only occasional occurrence, 

 in others, although intermittent, it occurs regularly, and still other species are apparently perpetually 

 parthenogenetic. Thus in many of the Gall-flies (Cynipidae) a parthenogenetic generation alternates 

 regularly with a sexual one, and in a few Tenthredinidae and Cynipidae the male insect is entirely 

 unknown, all the individuals belonging to the female sex, so that reproduction must be entirely 

 parthenogenetic, and the progeny always wholly female. In some Cynipidae, although the male is 

 very rare it is occasionally produced, but is probably useless, the virgin females being able to dispense 

 with the assistance of a male. 



On the other hand in some cases of parthenogenesis the progeny is entirely male. The 

 workers among the social ants, bees, and wasps sometimes lay unfertilized eggs, and these always 

 give rise to male individuals The same thing occurs with the queen hive-bee before fertilization, 

 and in some sawflies In a few species of the latter group, however, while the parthenogenetic 

 broods usually consist entirely of males, a female very occasionally appears. Whatever may be the 

 meaning of parthenogenesis and its significance is still very obscure it appears to tend to the 

 production of a brood in which the individuals are all of one sex, sometimes male, sometimes female. 



Among the higher Hymenoptera (ants, some bees and wasps) a remarkable development of 

 social life occurs, the individuals of a species living together in great societies consisting mainly of 

 imperfect females or ' workers ' who perform all the ordinary duties of the community ; they 

 construct, maintain, and defend the nest, and feed and tend the young. The work of reproduction 

 is undertaken by a single perfect female known as the queen, or by a small number of such females. 

 The males are short-lived, and of use only in the fertilization of the queens, 



HYMENOPTERA SESSILIVENTRES OR TENTHREDINIDAE 



Sawflies 



The Sawflies are as a rule sluggish insects with a weak heavy flight which is not long sustained. 

 They are fond of settling on flowers, especially Umbelliferae, and feed chiefly on pollen ; a few 

 species, however, devour the small insects frequenting flowers. They all possess in the female sex a 

 pair of remarkable sawing or piercing instruments which are used to cut or bore into the tissues of 

 plants in which the eggs are deposited. The larvae are exclusively vegetable feeders ; a few, like 

 Cephas, which feeds internally in stems of corn, and Sirex, which lives in the solid wood of trees, are 

 white fleshy grubs ; a few others inhabit galls, or bore into fruits, or mine or roll up leaves ; but the 

 great majority are caterpillar-like, and feed exposed on plants. These have from six to eight pairs 

 of prolegs in addition to the three pairs of thoracic legs, whereas a lepidopterous caterpillar never 

 has more than five pairs of prolegs. 



The larvae of some species of sawflies are at times very destructive to crops. Pteronus ribesti 

 sometimes completely defoliates the gooseberry bushes in gardens, and the slimy slug-like larva of 

 Eriocampoides limacinus occasionally does much damage to pear and other fruit trees. I have not 

 heard of any other species causing damage in Nottinghamshire. 



Parthenogenesis is very prevalent in this group, as has been repeatedly proved by rearing larvae 

 from unfertilized eggs laid in confinement by bred females. In nearly all the species females are 

 much more numerous than males ; indeed in some species males are very rare, and in others quite 

 unknown. On the other hand the parthenogenetically developed individuals of Pteronus ribesii are 

 almost always males. 



The list of Nottinghamshire sawflies is a somewhat meagre one, and will doubtless be greatly 

 extended when the group is properly worked. Tenthredopsis thornleyi is interesting as having been 

 founded by Pastor Konow on specimens collected by the Rev. A. Thornley in Nottinghamshire and 

 Lincolnshire in May and June, 1897. Nearly all the species enumerated below have been 

 determined either by Pastor Konow or the Rev. F. D. Morice. Unless otherwise stated they 

 were all collected by the Rev. A. Thornley or myself. 



LYDIDAE LYDIDAE (continued) 



Pamphilius sylvaticus, Linn. S. Leverton ; Tresteell Cephus pygmaeus, Linn. S. Leverton ; Trestvell 

 Wood Wood; Widmerpool, abundant in buttercup 



hortorum, Klug. Trestoell Wood flowers, 23 June, 1900 



depressus, Schrk. S. Leverton Macrocephus linearis, Schrk. Treswell Wood 



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