Caddis Flies in Milton Keynes

 

INSECT RECORDING

 

There is much more to moth trapping than moths. Over the last ten years I have recorded several hundreds of Macro and Micro moth species but many more insects are attracted to a light trap and become trapped. Some of the insect orders are; Mayflies, Earwigs, Shield bugs, Water bugs, Leafhoppers, Aphids, Lacewings, many sorts of Flies, assorted social Wasps and Ants, Ichneumons, various Ground Beetles, Chafers, a wide variety of Water Beetles, the occasional Butterfly and, once, a large Dragonfly.

 

Three years ago I became intrigued by the wide variety and number of Caddis Flies coming to the light trap. At first I saved specimens each month that looked different. Then finding no-one else interested in the insects locally, I resolved to learn more about them. The key in Collins field guide “The Insects of Britain and Northern Europe” is quite easy to follow and by examination of the spurs on each tibia, the form of the palps and, in some cases, the wing venation, a preserved specimen can be placed in one of the eighteen families of the order Trichoptera (hairy-winged insects).

 

 

THE CADDIS FLY

 

The name Caddis originates in folklore. It referred to a sort of tinker, a Caddyman, who travelled through villages with samples of his wares pinned to his coat. Caddis larvae build progressively a protective case from materials at hand. It is said that each species builds its case to a specific design from preferred materials. In practice, with a few exceptions, one can identify larval cases to family level only.

 

The Caddis or Sedge Fly has four wings held roof wise. They have six legs, longish antennae and two pairs of palps. The biggest drawback when first attempting an identification is that of the 190 UK species, a handful have easily recognisable features (e.g. wing marking) but most fit the description LBJs (little brown jobs), thereby demanding the use of a comprehensive, well used, up to date key to determine family, genus and species. The UK status of Caddis Fly species in 1985 was; common – ninety-five species, uncommon – sixty-six species and rare – twenty-nine species. Since the year 2000 more than thirty-five species have been identified for Milton Keynes with at least twenty or so awaiting confirmation or assistance with parts of the key. There are some very common species of Caddis Fly which can be found in Milton Keynes most times between April and November. They are: Glyphotaelius pellucidus, Limnephilus flavicornis, L. affinis, L. auricula, L. marmoratus, L. vittatus, L. lunatus, S. permistus, Hydropsyche pellucidula, H. radiatus, H. digitatus, Mystacides longicornis, Phryganea striata, H. angustipennis, Tinodes waeneri.

 

 

Life Cycle

 

Caddis flies pair very soon after leaving the water and mostly lay their several hundred eggs on, in or near water.  The tiny larvae appear in about two weeks.  As the larva grows it spins a sticky coating to which it progressively attaches various case building materials such as sand, leaves, sticks, shells or plant seeds in a style depending upon the species concerned.  The head and legs protrude from the case to allow movement and feeding.  About one third of UK species are not case builders, these build permanent silk nets attached to vegetation and filter food from the water flow.  The complete cycle takes about a year with pupation in early spring and emergence from April through to September/October depending upon the species.  Adults live for a few days to a week or two.

 

 

Fish and Fishing

 

The adult insect is heavily predated upon by bats and birds.  Fish feed on all stages of caddis, particularly on spent females which have returned to the water surface to lay eggs.  Anglers use artificial versions of larvae and adult caddis flies of the larger species for fly fishing (anglers use the term “sedge flies”).  Naturally, the correct species for the habitat and the time of year has to be adhered to so that the trout cannot tell the lure from the real thing.  This includes the actions of the fly struggling from its pupal case then fluttering along the water surface towards vegetation and safety.  Common names have been attributed by fisherman to a few species or groups of similar species.

 

 

The largest caddis are Phryganea grandis and P. striata, either can have the common name Great Red Sedge, Murragh or Northern Bustard.  The most common caddis, Limnophilus lunatus, is known as the Cinnamon Sedge.  A commonly used artificial caddis for trout fishing is called the Grannom, its scientific name is Brachycentrus subnubilis.  Of all the species only about forty or fifty are represented artificially, about fifty are so tiny as to be of no use as fishing flies.

 

Habitats in Milton Keynes

 

There is immense scope for research on water borne insects in Milton Keynes, the approximate lengths of the main water bodies are as follows:

 

n        River Great Ouse                  38 miles

n        River Ouzel                          16 miles

n        River Tove                             8 miles

n        Loughton Brook                     8 miles

n        Longmore Brook                    5 miles

n        Other small brooks             120 miles

n        Grand Union Canal               20 miles

                   Total               215 miles

 

Together with the above, including lakes and ponds, there are more than sixty potential major habitats for caddis to prosper.  During the early months of 2002 I made some 56 visits to 31 sites for access, visual and water pH checks.  I found sixteen sites where it was possible to easily observe from a few to hundreds of cased caddis busily moving about on the substrate or on submerged vegetation.  Little Linford Wood car park pond was perhaps the best site where I could identify several different families from close range.  Below the Haversham Viaduct emerging insects from the Great Ouse congregate on the large area of brickwork where I was able to easily collect and identify several species.  Caldecotte Lake has good numbers and Willen Lake has some sandy marginal areas which encourage a wide variety of species.  Blue Lagoon was the best site for access and observation with large areas of shallow clean water.  River observation is difficult with deep, mostly unclean water with steep overgrown banks.  Some of the least productive sites visited were Furzton and Mount Farm lakes which had considerable mobile silt, not much vegetation and high numbers of wildfowl.  At all sites the water pH was neutral.

 

 

Species List

 

A provisional list of caddis flies (Trichoptera) recorded in Milton Keynes during the period 2000-2002.  Those species more difficult to identify have been verified by Dr Ian Wallace of Liverpool Museum.  Twenty five specimens await verification.

 

C = Common               L = Local                     NR = Regionally Notable

 

Species

UK Status

Sites (LT = light trap)

Cyrnus flavidus

C & L

MLK.LT

C. trimaculatus

C

MLT.LT, G.U. Canal

Glyphotaelius pellucidus

C

MLK.GEH.LH.LT & various

Goera pilosa

C

MLK.LT

Halesus digitatus

C

MLK.LT

H. radiatus

C

MLK.LT

Hydropsyche angustipennis

C & NR

Tear Drop Lakes

H. contubernalis

C & NR

MLK.LT, Gt. Ouse

H. Pellucidula

C

MLK.GEH.LT, Haversham

Limnophilus affinis

C

MLK.GEH.LT

L. auricular

C

MLK.GEH.LH.LT

L. bipunctatus

L

MLK.LT

L. flavicornis

C

MLK.LT, HERC

L. lunatus

C

MLK.LH.LT

L. marmoratus

C

MLK.LT

L. sparsus

C

MLK.LT

L. vittatus

C

Olney Meadows

Lype phaeopa

C & NR

MLK.LT, G.U. Canal

Micropterna sequax

C

MLK.LT

Molanna angustata

NR

MLK.LT, Bradwell Lake

Mystacides longicornis

C & L

MLK.LT, Gt. Ouse

Neureclipsis bimaculata

C

MLK.LT

Oecetis ochracea

C

MLK.LT

Oligotricha striata

C & NR

MLK.LT, Willen Lake

Polycentropus flavomaculatus

C

MLK.LT

Stenophylax permistus

C

MLK.GEH.LT

Tinodes waeneri

C

MLK.LT, Caldecotte, Gayhurst

T. bicolor

C

MLK.LT

 

 

Further studies of distribution

 

The MV light trap is quite a blunt means of recording insect distribution, caddis flies as with moths and many other insects are attracted at night by what is such a powerful light from a wide circle of uncertain radius.  The more portable discreet actinic trap can be utilized in more specific safe (!!) habitats and left unattended e.g. in a woodland ride or a river bank etc.  Searching for late instar larvae in the shallows of rivers and lakes etc is the most accurate means of recording; however it does require the use of an additional set of identification keys for the caddis larvae.  Sweeping of canal tow paths and river or lakeside vegetation with a suitable net can be very productive particularly if there has been an insect emergence during the last day or so.  Beating overhead vegetation (using a tray and stick) is utilized where water passes through coniferous or deciduous woodland.  A combination of all the above methods is probably the best way to obtain a reasonable distribution of insect species based on 10km square mapping.

 

 

Uncommon Species

 

Several species become classified either as uncommon, local or notable etc, frequently as a result of under recording, because of insufficient recorders.  Many uncommon and rare species are habitat specialists; one such group is associated with wet/damp woodland, some where leaf litter collects in shallow pools or where the water flow ceases or dries up during the summer months.  We have such habitats in Milton Keynes and I hope to investigate them in due course.

 

Should anyone wish to assist me in any way in the research of caddis flies in Milton Keynes they are welcome to contact me via the Milton Keynes Natural History Society.

 

Mike Killeby

 

 

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