Category Theory without Objects

Our notion of category is that of [Eilenberg & Mac Lane, 1945]. We identify objects with their identity maps and we regard a diagram A--f-->B as a formula which asserts that A is the (identity map of the) domain of f and that B is the (identity map of the) codomain of f.

From the start of the PhD thesis of F. William Lawvere ( Functorial Semantics of Algebraic Theories and Some Algebraic Problems in the context of Functorial Semantics of Algebraic Theories, 1963).

Alloy Talk

Here is a good recent talk by Jay Parlar on using the Alloy Analyzer to find bugs in software designs.

Seasonal variation in the numbers of Delia Platura

Another bivoltine species, at least in southern UK.  Again based on specimens collected between 2014 and 2019, mostly in the Reading area but with a few from north Yorkshire and a few from the New Forest.

Bramble Stem Gall

A stem gall on bramble (Rubi fruticosus) caused by the larvae of the wasp Diastrophus rubi (Hymenoptera: Cynipidae). Identified using the key of Redfern & Shirley, 2011.

For images of the contents and later stages of these galls see here.

Specimen take in Thames Valley Park, Reading, UK on 2019-08-26.

Spring and Autumn Flies

More seasonal frequency plots for Muscid flies: First Eudasyphora cyanella which is commonest in spring:

And, second, the closely related Eudasyphora cyanicolor which is commonest in autumn:

These are from flies caught between 2014 and 2019 mainly on the Reading area but with with some from North Yorkshire and the New Forest.