82 THE ENTOMOLOGIST. 



I Metathoracic spiracles linear-elongate ; stigma of wings red. 



23. uniguttatus, 5 — 6 lines (s, a). 

 II Metathoracic spiracles rather short ; stigma fuscous. 



35. Panzeri, 41—6 hnes (Z, a). 

 ft Tibis red. 26, sputator, 6 hnes. 



THE COCOONS OF HYDROPHILUS PICEUS AND 

 HYDROBIUS FUSCIPES. 



By Abbott G. Laker. 



In the summer of 1878 I had the opportunity of examining 

 a good many cocoons of Hydrophiliis inceus, and, as I have seen 

 various and somewhat conflicting accounts given of these cocoons, 

 my notes on the subject may possibly be of some interest to 

 persons who have studied the habits of water insects. 



The cocoons were taken from a pond in the south-east of 

 London between June 9th and July 1st. They varied con- 

 siderably in size and shape, but on the average were about 

 llg- lines long b}^ lOf lines broad, and the height from the bottom 

 to the tip of the spike was about 17 lines. The walls of these 

 nests were composed of a substance very like whitey-brown 

 paper, but the portion of the cocoon immediately under the spike 

 was in each case closed simply by a loose downy material, which 

 would not be impervious to water, and as this part was submerged, 

 it is clear the enclosed eggs must be constantly moist. I have 

 seen it stated these cocoons are water-tight, but this is not 

 in accordance with my experience. 



The interior of the nest contains a loose silky substance 

 similar to that at the enc' immediately beneath the spike, and the 

 eggs are arranged with great regularity, their ends resting on the 

 bottom of the cocoon. The young larvae, when mature, break 

 through the silky substance mentioned above, but before they 

 are ready to emerge they are capable of some degree of move- 

 ment. 



The cocoons, whilst the eggs are unhatched, are very buoyant, 

 and, if allowed to float loose they are only submerged to about 

 two-thirds of their depth. I have found them floating, and only 

 surrounded with Confervce, but most of the specimens I have 

 taken have been attached to the long grass growing in the water 

 near the margin of the pond, or else attached to the under side of 



