226 Transactions. — Zoology. 



fig. 4) illustrating the veins and cells of the dipterous wing is 

 ■wholly ideal, and combines all the characters that are found 

 in the different families of the Order. The parts to which the 

 numbers refer are named in the explanation of the plate. 

 Some observations as to the relative value of the different 

 veins and cells in describing characters of genera and species 

 are given in Skuse's paper on the Australian Gcciclomyidce. 

 (vol. iii., Trans. Lin. Soc. N.S.W.). 



Family CECIDOMYID^. 



1. Ovum. 



Longer than broad, ends rounded, orange-red, yellow, or 

 whitish. The eggs are laid on the surface of leaves, in the 

 flowers of grasses, or beneath the bark of trees. The larva 

 usually escapes in a few days. In some species there is a 

 single annual generation, but in others eggs are laid at two or 

 more distinct times of the year. I have never been fortunate 

 enough to observe the eggs on any plants, but some of my 

 specimens deposited eggs after capture. 



2. Larva. 



The larva is rather a slender maggot, generally white in 

 colour, but often orange or red. The body consists of fourteen 

 segments, most of which are provided with stigmata. Head is 

 small and retractile, provided with soft and rudimentary 

 mouth-organs. A slender, corneous organ usually projects 

 from the first thoracic segment. This is called the anchor 

 process, or breast-bone. The function of this orgaii is not 

 yet certainly determined. Baron Osten-Sacken remarks that 

 its homology is unknown, and suggests that it is used for loco- 

 motion. He points out that it may represent the mentum, 

 and is therefore homologous with the boring mentum of the 

 larvffi of some Tipulidcs. Miss Ormerod suggests that the 

 organ is used to injure plant-tissues, in order that the nutri- 

 tive juices may be obtained more readily and in greater abun- 

 dance. The terminal segment of the body is frequently pro- 

 vided with stiff hairs, that aid apparently in locomotion. 



Some of the species undergo their metamorphosis from 

 larva to pupa in cocoons ; others bury themselves in the 

 ground ; while others have no special covering, and undergo 

 the change in the same place in which they have completed 

 their larval growth. 



Many years ago parthenogenesis was described in ceci- 

 domyid larvae. It appears to be of much the same nature 

 as that so well known in the various species of Aphis flies. 

 The ovaries of the larvae develope fully, and produce six or 

 more buds. These also grow and again produce buds, from 



