228 Prof. J. O. Westwood on some monstrous Insects. 



spinning any cocoon. The perfect moths which are pro- 

 duced from these individuals exliibit a curious mixture of 

 the parts of the imago and those of the larva ; the head 

 being small, furnished with two black compound eyes, the 

 thorax is incomplete, having the third segment similar to 

 the third ring of the larva ; the abdomen also resembles 

 that of the larva after its fourth moult both in form and 

 the number of its segments. The hind wings are long 

 and narrow, and the antenna? are greyish coloured, the 

 fore-wings somewhat elongated and narrow, and the hind 

 wings shorter and narrower (le ali superiori alquanto 

 lunghe e ristrette, le inferiori piu corte e strette). The 

 cause of this irregular transformation is supposed by 

 IMajoli to be an excessive warm temperature in the breed- 

 ing room, which prevents the caterpillar from producing 

 the exudation of the fluids necessary for the formation of 

 the chrysalis and obliges it to transform directly into the 

 moth. 



A somewhat similar instance of irregular development 

 in a moth ( Orgyia antiqua ?) was exhibited at the 

 November Meeting of the Entomological Society, in 

 Avhich the larva skin had only been partially shed, whilst 

 other parts of the insect had assumed the imago state, 

 and others showed the pupa skin. 



DIPTERA. 



Eristalis tenax. — This specimen (PI. VII. fig. 7), 

 which is in the Hopeian Collection, is remarkable at first 

 sight for the two frontal horns or processes arising from a 

 transverse portion of the head-case of the larva, which is 

 one of the rat-tailed species found in manure water. The 

 head itself of the imago is distinct ; but, as shown in figs, la 

 and 7i, it is enveloped in the delicate pellicle or cephalo- 

 theca of the pupa. 



Eristalis nemorum. — This specimen, the head of 

 which is represented in fig. 8, is also in the Hopeian 

 Collection, to which it was. presented by Sir Sidney 

 Saunders, agrees with the preceding in having retained 

 the head-case and two elongated appendages of the larva 

 on assumino; the imag-o state. 



